SGSN Principles(How Does It Works)

HUAWEI SGSN9810 Serving GPRS Support Node

V800R009

System Principle

Issue 03

Date 2009-05-27

Part Number 00413586

Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Huawei Technologies Co., Ltd. provides customers with comprehensive technical support and service. For anyassistance, please contact our local office or company headquarters.

Huawei Technologies Co., Ltd.Address: Huawei Industrial Base

Bantian, LonggangShenzhen 518129People's Republic of China

Website: http://www.huawei.com

Email: [email protected]

Copyright © Huawei Technologies Co., Ltd. 2009. All rights reserved.No part of this document may be reproduced or transmitted in any form or by any means without prior writtenconsent of Huawei Technologies Co., Ltd. Trademarks and Permissions

and other Huawei trademarks are the property of Huawei Technologies Co., Ltd.All other trademarks and trade names mentioned in this document are the property of their respective holders. NoticeThe information in this document is subject to change without notice. Every effort has been made in thepreparation of this document to ensure accuracy of the contents, but the statements, information, andrecommendations in this document do not constitute a warranty of any kind, express or implied.

Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

http://www.huawei.com

mailto:[email protected]

Contents

About This Document.....................................................................................................................1

1 System Structure of SGSN9810...............................................................................................1-11.1 Overview of SGSN9810..................................................................................................................................1-21.2 Hardware Structure.........................................................................................................................................1-3

1.2.1 SGSN subracks.......................................................................................................................................1-31.2.2 PSM Subrack..........................................................................................................................................1-51.2.3 SGSN Board...........................................................................................................................................1-6

1.3 Software Structure...........................................................................................................................................1-81.3.1 Platform System..................................................................................................................................1-101.3.2 Service System.....................................................................................................................................1-101.3.3 Charging System..................................................................................................................................1-111.3.4 O&M System........................................................................................................................................1-11

2 Principle of the Hardware........................................................................................................2-12.1 Interconnection Between PSM Subracks.......................................................................................................2-22.2 Buses in PSM Subracks...................................................................................................................................2-3

2.2.1 Shared Resource Bus..............................................................................................................................2-32.2.2 H.110 Bus...............................................................................................................................................2-42.2.3 Serial Port Bus........................................................................................................................................2-6

2.3 Power Supply SubSystem...............................................................................................................................2-72.3.1 Structure.................................................................................................................................................2-72.3.2 Power Supply Monitoring...................................................................................................................2-10

2.4 Clock Synchronization Subsystem................................................................................................................2-122.4.1 Technical Specifications......................................................................................................................2-122.4.2 Structure...............................................................................................................................................2-142.4.3 Clock Interface Part..............................................................................................................................2-152.4.4 Clock Distribution Part.........................................................................................................................2-162.4.5 Clock Control Part................................................................................................................................2-18

2.5 Equipment Monitoring Subsystem................................................................................................................2-182.5.1 Fan Monitoring.....................................................................................................................................2-182.5.2 Equipment Room Environment Monitoring........................................................................................2-19

3 Principle of the Platform System............................................................................................3-13.1 The location of the platform system................................................................................................................3-2

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle Contents

Issue 03 (2009-05-27) Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

i

3.2 Platform Management Subsystem...................................................................................................................3-33.2.1 The Structure of Platform Management Subsystem..............................................................................3-33.2.2 Load Management..................................................................................................................................3-43.2.3 Startup Management..............................................................................................................................3-63.2.4 Switchover Management........................................................................................................................3-73.2.5 Patch Processing.....................................................................................................................................3-9

3.3 Internal Communication Subsystem.............................................................................................................3-113.3.1 Structure...............................................................................................................................................3-113.3.2 The procedure for exchanging data between the subracks...................................................................3-12

4 Principle of the Service System...............................................................................................4-14.1 The structure of the service processing system...............................................................................................4-24.2 IP Routing Subsystem.....................................................................................................................................4-3

4.2.1 The structure of IP Routing Subsystem..................................................................................................4-34.2.2 Principle of IP routing subsystem..........................................................................................................4-5

4.3 Gb Interface Subsystem..................................................................................................................................4-74.3.1 The structure of Gb Interface Subsystem...............................................................................................4-74.3.2 The procedure for processing Gb packets in the Gb interface subsystem..............................................4-9

4.4 Iu Interface Control Plane Subsystem...........................................................................................................4-114.4.1 The structure of Iu Interface Control Plane Subsystem.......................................................................4-114.4.2 The procedure for signaling processing in the Iu interface signaling subsystem................................4-14

4.5 Gn/Gp Interface Subsystem .........................................................................................................................4-164.5.1 The structure of Gn/Gp Interface Subsystem ......................................................................................4-164.5.2 The procedure for User Data forwarding.............................................................................................4-184.5.3 Procedure for Processing Gn/Gp Signaling Data.................................................................................4-204.5.4 Procedure for DNS Resolution.............................................................................................................4-214.5.5 Procedure for NTP Synchronization....................................................................................................4-22

4.6 Signaling Subsystem.....................................................................................................................................4-234.6.1 The structure of Signaling Subsystem..................................................................................................4-234.6.2 Procedure for L3 Signaling .................................................................................................................4-26

4.7 Typical Data Processing Procedure...............................................................................................................4-284.7.1 2.5G signaling data flow......................................................................................................................4-284.7.2 3G signaling data flow.........................................................................................................................4-304.7.3 2.5G service data flow..........................................................................................................................4-314.7.4 3G service data flow.............................................................................................................................4-32

5 Principle of the Charging System...........................................................................................5-15.1 The location of the charging system in the SGSN..........................................................................................5-25.2 The structure of the modules in the charging system......................................................................................5-35.3 The procedure for generating a CDR..............................................................................................................5-45.4 Processing and Sending a CDR.......................................................................................................................5-6

6 Principle of the O&M System..................................................................................................6-16.1 The location of the O&M system in the SGSN...............................................................................................6-3

ContentsHUAWEI SGSN9810 Serving GPRS Support Node

System Principle

ii Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)

6.2 The structure of the modules in the O&M system..........................................................................................6-46.3 Configuration Management.............................................................................................................................6-56.4 Performance Measurement..............................................................................................................................6-7

6.4.1 The basic concepts of performance measurement..................................................................................6-76.4.2 Procedure for performance measurement...............................................................................................6-8

6.5 Alarm Management.......................................................................................................................................6-106.6 Query and Control.........................................................................................................................................6-136.7 Security Management....................................................................................................................................6-14

6.7.1 Domain Management...........................................................................................................................6-146.7.2 User Authorities...................................................................................................................................6-156.7.3 User Name and Password.....................................................................................................................6-156.7.4 Command Groups................................................................................................................................6-16

6.8 User or Interface Tracing..............................................................................................................................6-176.9 Log Management...........................................................................................................................................6-186.10 External Maintenance Interface...................................................................................................................6-19

6.10.1 Command Input and Output Interface................................................................................................6-206.10.2 SNMP Interface..................................................................................................................................6-216.10.3 SSH.....................................................................................................................................................6-21

Index.................................................................................................................................................i-1

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle Contents


iii

Figures

Figure 1-1 Location of the SGSN9810 in a GPRS/UMTS network....................................................................1-2Figure 1-2 Hardware configuration of the SGSN9810.........................................................................................1-4Figure 1-3 Boards in the switching subrack.........................................................................................................1-5Figure 1-4 Boards in the basic subrack................................................................................................................1-6Figure 1-5 Boards in the extended subrack for both 2.5G and 3G services ........................................................1-6Figure 1-6 Structure of the SGSN9810 software.................................................................................................1-9Figure 2-1 Interconnection between the PSM subracks.......................................................................................2-2Figure 2-2 Buses in the PSM subrack..................................................................................................................2-3Figure 2-3 Shared resource bus............................................................................................................................2-4Figure 2-4 H.110 bus............................................................................................................................................2-5Figure 2-5 Principle of the USPU switchover......................................................................................................2-6Figure 2-6 Serial port bus.....................................................................................................................................2-7Figure 2-7 Power input part..................................................................................................................................2-8Figure 2-8 Power distribution part.......................................................................................................................2-9Figure 2-9 Principles of monitoring the PDB....................................................................................................2-10Figure 2-10 Principles of monitoring the UPWR...............................................................................................2-11Figure 2-11 Maximum allowed input jitter and lower limit of wander..............................................................2-14Figure 2-12 Architecture of the clock synchronization system..........................................................................2-15Figure 2-13 Procedure for clock distribution inside the PSM subrack..............................................................2-17Figure 2-14 Fan monitoring...............................................................................................................................2-18Figure 2-15 Equipment room environment monitoring.....................................................................................2-19Figure 3-1 Location of the platform system in the SGSN....................................................................................3-2Figure 3-2 Modules inside the platform management subsystem........................................................................3-3Figure 3-3 Loading channels for each board........................................................................................................3-5Figure 3-4 Sequence of board startup...................................................................................................................3-7Figure 3-5 Switchover procedure.........................................................................................................................3-8Figure 3-6 Working principle of the software patch..........................................................................................3-10Figure 3-7 Transfer of patch states.....................................................................................................................3-11Figure 3-8 Logical structure of the internal communication subsystem............................................................3-12Figure 3-9 Procedure for exchanging data between the subracks......................................................................3-13Figure 4-1 Structure of the service system...........................................................................................................4-2Figure 4-2 Modules inside the IP routing subsystem ..........................................................................................4-4Figure 4-3 Procedure for processing IP packets in the IP routing subsystem......................................................4-6

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle Figures


v

Figure 4-4 Modules inside the Gb interface subsystem ......................................................................................4-8Figure 4-5 Procedure for processing Gb packets in the Gb interface subsystem...............................................4-10Figure 4-6 Modules inside the Iu interface control plane interface subsystem..................................................4-12Figure 4-7 Procedure for signaling processing in the Iu interface signaling subsystem....................................4-15Figure 4-8 Modules inside the Gn/Gp interface subsystem...............................................................................4-17Figure 4-9 Procedure for forwarding user data..................................................................................................4-19Figure 4-10 Procedure for processing the Gn/Gp signaling data.......................................................................4-20Figure 4-11 Procedure for DNS resolution .......................................................................................................4-21Figure 4-12 Procedure for NTP synchronization ..............................................................................................4-22Figure 4-13 Modules inside the signaling subsystem........................................................................................4-24Figure 4-14 Procedure for signaling processing ................................................................................................4-27Figure 4-15 Processing procedure for 2.5G uplink signaling data flow ............................................................4-29Figure 4-16 Processing procedure for 3G uplink signaling data flow ...............................................................4-30Figure 4-17 Processing procedure for 2.5G uplink service data flow ...............................................................4-31Figure 4-18 Processing procedure for 3G uplink service data flow...................................................................4-32Figure 5-1 Location of the charging system in the SGSN................................................................................... 5-2Figure 5-2 Structure of the charging subsystems ................................................................................................5-3Figure 5-3 Charging flow points for the mobility management service.............................................................. 5-5Figure 5-4 Procedure for sending a CDR.............................................................................................................5-7Figure 6-1 Location of the O&M system in the SGSN........................................................................................6-3Figure 6-2 Hierarchy of the O&M system........................................................................................................... 6-4Figure 6-3 Composition of the O&M system.......................................................................................................6-5Figure 6-4 Configuration management flow........................................................................................................6-6Figure 6-5 Procedure for performance measurement...........................................................................................6-8Figure 6-6 Alarm management flow..................................................................................................................6-11Figure 6-7 Query and control flow.....................................................................................................................6-13Figure 6-8 Procedure for user authentication.....................................................................................................6-15Figure 6-9 Procedure for user tracing or interface tracing ................................................................................6-18Figure 6-10 External O&M interfaces of the SGSN .........................................................................................6-20Figure 6-11 Structure and flow of SNMP..........................................................................................................6-21Figure 6-12 Establishing an SSH channel between the SGSN and LMT..........................................................6-22

FiguresHUAWEI SGSN9810 Serving GPRS Support Node

System Principle

vi Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)

Tables

Table 1-1 Boards in the SGSN ............................................................................................................................1-7Table 2-1 Connection description in the PSM subrack......................................................................................2-10Table 2-2 Technical specifications of the clock synchronization system...........................................................2-13Table 5-1 MS status in the M-CDR generation procedure...................................................................................5-5Table 5-2 Description of the charging flow points...............................................................................................5-6Table 6-1 User groups and authorities................................................................................................................6-15Table 6-2 Command group description..............................................................................................................6-16

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle Tables


vii

About This Document

PurposeThis manual describes the following content:

l Position, functions, hardware structure, and software structure of the SGSN

l Implementation principles of the hardware, platform system, service system, chargingsystem, and O&M system

Related VersionsThe following table lists the product versions related to this document.

Product Name Version

SGSN9810 V800R009

Intended AudienceThe intended audiences of this document are:

l Marketing staff

l Installation engineers & technicians

l Operation & maintenance personnel

Organization1 System Structure of SGSN9810

The syetem structure of SGSN consists of hardware structure and software structure

2 Principle of the Hardware

The principle of the hardware system involves principles of the interconnection betweensubracks, internal cables, power supply, clocks, and monitoring system.

3 Principle of the Platform System

The platform system consists of the platform management subsystem and internalcommunication subsystem. The system realizes board drive, communications, and datamanagement.

4 Principle of the Service System

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle About This Document


1

The service system consists of the IP routing subsystem, Gb interface subsystem, Iu interfacecontrol plane subsystem, Gn/Gp interface subsystem, and signaling subsystem. The servicesystem processes the external interface protocol and high-level signaling for the SGSN andforwards user data.

5 Principle of the Charging System

The charging system operates in the USPU, UGTP, and UCDR boards. The charging systemcollects, codes, buffers, and sends CDRs as well as provides charging information for the billingcenter.

6 Principle of the O&M System

The O&M system is a management center of the SGSN. The O&M system provides interactiveinterfaces between an operator and the SGSN.

ConventionsSymbol Conventions

The symbols that may be found in this document are defined as follows.

Symbol Description

Indicates a hazard with a high level of risk, which if notavoided,will result in death or serious injury.

Indicates a hazard with a medium or low level of risk, whichif not avoided, could result in minor or moderate injury.

Indicates a potentially hazardous situation, which if notavoided,could result in equipment damage, data loss,performance degradation, or unexpected results.

Indicates a tip that may help you solve a problem or savetime.

Provides additional information to emphasize or supplementimportant points of the main text.

General Conventions

The general conventions that may be found in this document are defined as follows.

Convention Description

Times New Roman Normal paragraphs are in Times New Roman.

Boldface Names of files, directories, folders, and users are inboldface. For example, log in as user root.

Italic Book titles are in italics.

About This DocumentHUAWEI SGSN9810 Serving GPRS Support Node

System Principle

2 Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)


Courier New Examples of information displayed on the screen are inCourier New.

Command Conventions

The command conventions that may be found in this document are defined as follows.


Boldface The keywords of a command line are in boldface.

Italic Command arguments are in italics.

[ ] Items (keywords or arguments) in brackets [ ] are optional.

{ x | y | ... } Optional items are grouped in braces and separated byvertical bars. One item is selected.

[ x | y | ... ] Optional items are grouped in brackets and separated byvertical bars. One item is selected or no item is selected.

{ x | y | ... }* Optional items are grouped in braces and separated byvertical bars. A minimum of one item or a maximum of allitems can be selected.

[ x | y | ... ]* Optional items are grouped in brackets and separated byvertical bars. Several items or no item can be selected.

GUI Conventions

The GUI conventions that may be found in this document are defined as follows.


Boldface Buttons, menus, parameters, tabs, window, and dialog titlesare in boldface. For example, click OK.

> Multi-level menus are in boldface and separated by the ">"signs. For example, choose File > Create > Folder .

Keyboard Operations

The keyboard operations that may be found in this document are defined as follows.

Format Description

Key Press the key. For example, press Enter and press Tab.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle About This Document


3

Format Description

Key 1+Key 2 Press the keys concurrently. For example, pressing Ctrl+Alt+A means the three keys should be pressed concurrently.

Key 1, Key 2 Press the keys in turn. For example, pressing Alt, A meansthe two keys should be pressed in turn.

Mouse Operations

The mouse operations that may be found in this document are defined as follows.

Action Description

Click Select and release the primary mouse button without movingthe pointer.

Double-click Press the primary mouse button twice continuously andquickly without moving the pointer.

Drag Press and hold the primary mouse button and move thepointer to a certain position.

Update HistoryUpdates between document versions are cumulative. Therefore, the latest document versioncontains all updates made to previous versions.

Updates in Issue 03 (2009-05-27)

Remove SGSN N+1 function.


Bug revision.


Initial field trial release.

About This DocumentHUAWEI SGSN9810 Serving GPRS Support Node

System Principle

4 Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)

1 System Structure of SGSN9810

About This Chapter

The syetem structure of SGSN consists of hardware structure and software structure

1.1 Overview of SGSN9810The SGSN9810 is a device in a core network–packet switched (CN–PS) domain of the generalpacket radio system (GPRS) or universal mobile telecommunications system(UMTS).

1.2 Hardware StructureThe SGSN9810 consists of cabinets,Subrack,Board.

1.3 Software StructureEach board in the SGSN9810 has its own software. Based on the functions of the software, theSGSN9810 software is divided into various software systems.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 1 System Structure of SGSN9810


1-1

1.1 Overview of SGSN9810The SGSN9810 is a device in a core network–packet switched (CN–PS) domain of the generalpacket radio system (GPRS) or universal mobile telecommunications system(UMTS).

Figure 1-1 shows the location of the SGSN9810 in a GPRS/UMTS network.

Figure 1-1 Location of the SGSN9810 in a GPRS/UMTS network

Other PLMN

NodeB

RNC

UMTS UTRAN

RANGSM/GPRS BSS

BSC

CN-CS

MSC/VLRHLR

SGSNFirewall

BG

DNSServer

SMS-GMSCSMS-IWMSC

GMSC

BillingCenter

CG

GGSN/FA

CN-PS

DNSServer

WAPGateway

AAAServer

Firewall

BTSMS

HA

CoreNetwork

PSTN,ISDN

Internet,Intranet,

etc.

SS7

EIR

MS: mobile station RAN: radio access network

CN-CS: core network – circuit switcheddomain

CN-PS: core network – packet switched domain

BSS: base station subsystem UTRAN: UMTS terrestrial radio access network

BTS: base transceiver station BSC: base station controller

RNC: radio network controller BG: border gateway

SGSN: serving GPRS Support Node HA: home agent

1 System Structure of SGSN9810HUAWEI SGSN9810 Serving GPRS Support Node

System Principle

1-2 Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)

CG: charging gateway DNS: domain name service

GGSN/FA: gateway GPRS support node/foreign agent

AAA: authentication, authorization, andaccounting

MSC/VLR: mobile service switching center/visitor location register

HLR: home location register

WAP: wireless access protocol EIR: equipment identification register

SMS-GMSC: short message servicegateway MSC

SMS-IWMSC: short message serviceinterworking MSC

GMSC: gateway MSC PSTN: public switched telephone network

ISDN: integrated services digital network SS7: CCITT signaling system No.7

The serving GPRS support node (SGSN) provides the following functions:

l Routing and forwarding of data packets

l Encryption and authentication

l Session management

l Mobility management

l Logical link management

l Generation and output of charging data records (CDRs)

1.2 Hardware StructureThe SGSN9810 consists of cabinets,Subrack,Board.

1.2.1 SGSN subracksThe SGSN9810 consists of one or more cabinets. Each cabinet houses four subracks that arecalled packet service module (PSM) subracks.

1.2.2 PSM SubrackEach PSM subrack has 21 slots. Boards can be inserted from both the front side and the rear sideof the subrack.PSM subracks are classified into the switching subrack, basic subrack, andextended subrack.

1.2.3 SGSN BoardThe boards in the SGSN process services for the SGSN.

1.2.1 SGSN subracksThe SGSN9810 consists of one or more cabinets. Each cabinet houses four subracks that arecalled packet service module (PSM) subracks.



1-3

Each PSM subrack has 21 slots. Boards can be inserted from both the front side and the rear sideof the subrack.

Figure 1-2 shows the SGSN9810 hardware in full configuration.

Figure 1-2 Hardware configuration of the SGSN9810

Air Deflector

Dummy Pannel

Power Distribution Box

UGBI

UGBI

UGBI

UGBI

USPU

USPU

URCU

URCU

USPU

USPU

UGBI

UGBI

UGBI

UGBI

UALU

UPWR

UPWR

UGTP

UGTP

UGBI

UGBI

UGFU

UGFU

URCU

URCU

UOMU

UOMU

UGTP

UGTP

UALU

UPWR

UPWR

UICP

UICP

USPU

USPU

USPU

USPU

URCU

URCU

USPU

USPU

UGBI

UGBI

UGBI

UGBI

UALU

UPWR

UPWR

PSM Subrack

UCDR

UCDR

UGFU

UGFU

UFCU

UFCU

URCU

URCU

UFCU

UFCU

UFCU

UFCU

UGFU

UGFU

UALU

UPWR

UPWR

PSM Subrack

PSM Subrack

PSM Subrack

Air Deflector

Air Deflector


System Principle


Issue 03 (2009-05-27)

1.2.2 PSM SubrackEach PSM subrack has 21 slots. Boards can be inserted from both the front side and the rear sideof the subrack.PSM subracks are classified into the switching subrack, basic subrack, andextended subrack.

The following slots are fixedly configured:

l Slot 6 and Slot 8: configured with the URCU (front board) and the UBIU (back board)

l Slot 7 and Slot 9: configured with the UACU (back board)

l Slot 17 and Slot 19: configured with the UPWR, which occupies two slots and is insertedfrom both the front side and the rear side of the slot

l Slot 16: configured with the UALU (front board)

Other slots are common slots, which can be configured with any types of boards. Based on theconfigurations for different boards, PSM subracks are classified into the switching subrack, basicsubrack, and extended subrack.

Switching Subrack

The PSM subrack configured with the frame connect unit (UFCU) is called the switchingsubrack. The SGSN can be and must be configured with only one switching subrack.

Figure 1-3 shows the switching subrack in full configuration.

Figure 1-3 Boards in the switching subrack

UPIU

UPIU

UPIU

UPIU

UACU

U

U

UACU

UPIU

UPIU

UPWR

UPWR

UPWR

UPIU

UBIU

BI

UFCU

UGFU

UALU

UPWR

UCDR

UCDR

UGFU

UFCU

URCU

UFCU

UFCU

UFCU

UFCU

UGFU

UGFU

URCU

UBSU

UBSU

UPIU

UPIU

UPIU

NOTE

In Figure 1-3, the boards in the upper part of the subrack are inserted from the rear, and the boards in thelower part are inserted from the front.

Basic Subrack

The PSM subrack configured with the packet service O&M unit (UOMU) is called the basicsubrack. The SGSN can be and must be configured with only one basic subrack.

Figure 1-4 respectively show the boards in the basic subrack.



1-5

Figure 1-4 Boards in the basic subrack

UBIU

URCU

UACU

UBIU

URCU

UACU

UFSU

UOMU

UFSU

UOMU

ULAN

UCKI

UGTP

UCKI

UALU

UPWR

UPWR

UPWR

UPWR

UGTP

USPU

USPU

NOTE

In the above three figure, the boards in the upper part of the subrack are inserted from the rear, and theboards in the lower part are inserted from the front.

Extended Subrack

Other PSM subracks except the switching subrack and basic subrack are called the extendedsubracks. The SGSN can be configured with no extended subrack or with multiple extendedsubracks.

An extended subrack can be configured to process 2.5G services, 3G services, or both of them.

Figure 1-5 shows the boards in the extended subrack for both 2.5G and 3G services.

Figure 1-5 Boards in the extended subrack for both 2.5G and 3G services

UEPI

UGBI

UEPI

UGBI

UEPI

UGBI

UEPI

UGBI

UEPI

USPU

UEPI

USPU

UBIU

URCU

UACU

UBIU

URCU

UACU

UEPI

UEPI

UEPI

UEPI

UICP

UICP

UALU

UPWR

UPWR

UPWR

UPWR

USPU

USPU

USPU

USPU

NOTE

In Figure 1-5, the boards in the upper part of the subrack are inserted from the rear, and the boards in thelower part are inserted from the front.

1.2.3 SGSN BoardThe boards in the SGSN process services for the SGSN.

Table 1-1 lists all the boards in the SGSN.


System Principle


Issue 03 (2009-05-27)

Table 1-1 Boards in the SGSN

Name Description

UACU Auxiliary control unit

UAIC Asynchronous transfer mode (ATM)interface card

UALU Alarm unit

UBIU Back interface unit

UBSU Back storage unit

UCDR Charging detail record unit

UCKI Clock unit

UEEC Ethernet electric interface card

UEFC Ethernet fiber interface card

UEPC Encryption processing card

UEPI E1 processing interface unit

UTPI T1 processing interface unit

UFCU Frame connect unit

UFEU Frame relay enhance unit

UFIU Fiber interface unit

UFSU PSM flash disk storage unit

UGBI Gb interface unit

UGFU GPRS tunneling protocol (GTP) forwardingunit

UGTP GTP processing unit

UICP Iu_PS control processing unit

ULAN LAN-switch card

UOMU Packet service O&M unit

UPIU Packet interface unit

URCU Sub-rack control unit

USIG SIGTRAN process unit

USPU Packet service signal processing unit

USS7 CCITT signaling system No.7 (SS7)signaling link processing unit



1-7

Name Description

UPWR PSM power module

1.3 Software StructureEach board in the SGSN9810 has its own software. Based on the functions of the software, theSGSN9810 software is divided into various software systems.

As shown in Figure 1-6.


System Principle


Issue 03 (2009-05-27)

Figure 1-6 Structure of the SGSN9810 software

BSS

UICP

Platformmanagement

OM

Gbinterface

subsystem

Platformmanagement

OM

UGBI

Signalingsubsystem

Platformmanagement

OM

USIG

Signalingsubsystem

Platform management

OM

Chargingsystem

USPUUGTP

Platform management

OM

Chargingsystem

URCU

Platform management

OM

Internalcommunication

subsystem

UFCU


subsystem

Platformmanagement

OM

UGFU

IP routingsubsystem

Platformmanagement

OM

Gn/Gpinterface

subsystem

UOMU

Platformmanagement

OM

UCDR

Chargingsystem

Platformmanagement

OM

BSS

No.7signalling

node, suchas HLR

RNCIP node,such asGGSN

LMT

BUS

BUS

Service subrack

Switching subrack

Iu interfacecontrolplane

subsystem

Gn/Gpinterface

subsystem

E1 E1

Network cable Fiber cable

Fiber cable

Fiber cable

Fiber cable ornetwork cable

NOTE

When Gb over IP and SS7 over IP functions are used, the UGFU provides the interfaces to connect theSGSN with the HLR and BSS.

The SGSN9810 software consists of the following four systems:

l Platform system

l Service system



1-9

l Charging system

l O&M system

The following sections describe the functions of each system.

1.3.1 Platform SystemThe platform system consists of the platform management subsystem and internalcommunication subsystem. The platform system realizes board drive, communications betweenboards, and data management.

1.3.2 Service SystemThe service system consists of the internet protocol (IP) routing subsystem, Gb interfacesubsystem, Iu interface control plane subsystem, Gn/Gp interface subsystem, and signalingsubsystem. The service system processes the external interface protocols and high-levelsignaling for the SGSN and transfers user data.

1.3.3 Charging SystemThe charging system collects, codes, buffers, and sends CDRs and provides charging informationfor the billing center.

1.3.4 O&M SystemThe O&M system provides the O&M interfaces for the SGSN. The O&M system realizes alarmmanagement, performance statistics, signaling tracing, in addition to command resolution andprocessing.

1.3.1 Platform SystemThe platform system consists of the platform management subsystem and internalcommunication subsystem. The platform system realizes board drive, communications betweenboards, and data management.

The subsystems of the platform system has the following functions:

l Platform management subsystemIt realizes operation system, hardware drive, communications between boards,configuration data, and user data management. It is the foundation on which other softwaremodules operate.It works in all the boards.

l Internal communication subsystemIt realizes routing and forwarding of data or signaling between subracks.It works in the UFCU of the switching subrack, in addition to the URCU, UCDR, andUOMU of the service subrack. The main functions are realized in the UFCU.

NOTE

Unless specially mentioned, the boards involved in this manual include subboards and back boards. Forexample, the UOMU mentioned above includes the UOMU and UFSU.

1.3.2 Service SystemThe service system consists of the internet protocol (IP) routing subsystem, Gb interfacesubsystem, Iu interface control plane subsystem, Gn/Gp interface subsystem, and signalingsubsystem. The service system processes the external interface protocols and high-levelsignaling for the SGSN and transfers user data.

The subsystems of the service system has the following functions:


System Principle


Issue 03 (2009-05-27)

l IP routing subsystem

It provides the interfaces to connect the SGSN with the external IP networks and carriesout IP routing and security check.

The IP routing subsystem works in the UGFU board.

l Gb interface subsystem

It realizes the functions of the physical layer, frame relay (FR), network service (NS), basestation subsystem GPRS protocol (BSSGP), subnetwork dependent convergence protocol(SNDCP), and logical link control (LLC) layers for the Gb interface.

The Gb interface subsystem works in the UGBI board.

l Iu interface control plane subsystem

It realizes the functions of the signaling ATM adaptation layer (SAAL), message transferpart broadband (MTP3B), signaling connection and control part (SCCP), and radio accessnetwork application part (RANAP) layers for the Iu interface control plane.

The Iu interface subsystem works in the UICP board.

l Gn/Gp interface subsystem

It realizes GTP-C signaling forwarding, network time protocol (NTP) client, domain nameservice (DNS) client, and GPRS tunnel protocol (GTP) data packets forwarding betweenthe Gn/Gp interface and Iu interface or between the Gn/Gp interface and Gb interface

The Gn/Gp interface subsystem works in the UGTP and UGFU boards.

l Signaling subsystem

It realizes the functions of message transfer part (MTP) L1/L2/L3, or simple controltransmission protocol (SCTP) and SS7 MTP3-user adaptation (M3UA) layers ofSIGTRAN for SS7 in addition to the functions of SCCP, transaction capability applicationpart (TCAP), mobile application part (MAP), CAMEL application part (CAP), mobilitymanagement (MM), session management (SM), short message service (SMS), customizedapplications for mobile network enhanced logic (CAMEL), and base station subsystemapplication part (BSSAP+) protocol layers.

The signaling subsystem works in the USPU and USIG boards. The USIG board realizesthe functions of SCTP and M3UA layers, while other functions are realized by the USPUboard.

1.3.3 Charging SystemThe charging system collects, codes, buffers, and sends CDRs and provides charging informationfor the billing center.

The charging system operates in the USPU, UGTP, and UCDR boards.

1.3.4 O&M SystemThe O&M system provides the O&M interfaces for the SGSN. The O&M system realizes alarmmanagement, performance statistics, signaling tracing, in addition to command resolution andprocessing.

The O&M system consists of the host software and terminal software.

l The host software works in all the boards. Its main functions are realized in the UOMU.

l The terminal software works in the PC and provides the man machine interface.



1-11

2 Principle of the Hardware

About This Chapter

The principle of the hardware system involves principles of the interconnection betweensubracks, internal cables, power supply, clocks, and monitoring system.

2.1 Interconnection Between PSM SubracksThe SGSN consists of multiple subracks. The subracks communicate with each other throughthe switching subrack.

2.2 Buses in PSM SubracksThe buses in the PSM subrack transfer the data, clocks, and control signals between the boardsin the subrack.

2.3 Power Supply SubSystemThe power supply subsystem powers the entire SGSN9810. It requires high reliability. TheSGSN9810 adopts a dual-circuit backup and point-to-point monitoring method in the design.

2.4 Clock Synchronization SubsystemWhen the SGSN9810 provides narrowband signaling to connect with other devices or framerelay (FR) to connect with the base station subsystem (BSS), the clock synchronizationsubsystem is required to be configured to carry out clock synchronization.

2.5 Equipment Monitoring SubsystemThe equipment monitoring subsystem consists of fan monitoring and equipment roomenvironment monitoring to ensure that the SGSN can work in a normal environment.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 2 Principle of the Hardware


2-1

2.1 Interconnection Between PSM SubracksThe SGSN consists of multiple subracks. The subracks communicate with each other throughthe switching subrack.


Figure 2-1 Interconnection between the PSM subracks

Switching subrack

UBIU

URCU

UBIU

URCU

UPIU

UFCU

UPIU

UFCU

UPIU

UFCU

UPIU

UFCU

UPIU

UFCU

UPIU

UFCU

UBIU

URCU

UBIU

URCU

UBIU

URCU

UBIU

URCU

UFSU

UOMU

UFSU

UOMU

UBSU

UCDR

UBSU

UCDR

ULAN

The UBIUs, back boards of the URCUs in each PSM subrack, connect to the UPIUs, back boardsof the UFCUs in the switching subrack through SDH transport module-1 (STM-1) fibers.Through information exchange and routing of the UFCU, the boards in different PSM subrackscan communicate with each other.

Though the UOMUs and UCDRs are inserted in the PSM subrack, they cannot directlycommunicate with the URCUs in the same subrack. The back boards of the UOMUs and UCDRsconnect with the UPIUs, back boards of the UFCUs. Through information exchange and routingof the UFCU, the UOMUs and UCDRs can communicate with all other boards.

The UFSUs, back boards of the UOMUs, connect with the ULANs and UBIUs, back boards ofthe URCUs in the switching subrack through network cables to form an initial loading channelfor the active URCU when the system is power-on.

2 Principle of the HardwareHUAWEI SGSN9810 Serving GPRS Support Node

System Principle


Issue 03 (2009-05-27)

2.2 Buses in PSM SubracksThe buses in the PSM subrack transfer the data, clocks, and control signals between the boardsin the subrack.

The PSM subrack contains the following three types of buses, as shown in Figure 2-2.

l Shared resource bus

l H.110 bus

l Serial port bus

Figure 2-2 Buses in the PSM subrack

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

UACU

UBIU

UACU

UBIU

URCU

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

URCU

UALU

Shared resourebus B

Shared resourebus A

H.110 busSerial port bus

BB

BB: back board

FB: front board

2.2.1 Shared Resource BusThe shared resource bus is also called OSTA bus.

2.2.2 H.110 BusThe H.110 bus provides the following functions: Carrying out service switchover between theactive and standby USPUs or UGBIs. Providing a transmission channel for reference clock inthe subrack

2.2.3 Serial Port BusThe serial port bus carries out control, load, and state query for the boards that are controlled bythe center processing unit (CPU) in the subrack but not connected to the shared resource bus.These boards include the UCKI, UEPI, and UALU.

2.2.1 Shared Resource BusThe shared resource bus is also called OSTA bus.

Functions

Through the shared resource bus, the URCU carries out loading, managing, and maintaining theUSPU, UICP, UGBI, UGTP and USIG boards in the subrack.



2-3

NOTE

Though the UOMUs and UCDRs are inserted in the PSM subrack, they communicate with the URCUs inthe switching subrack through fibers instead of the shared resource bus.

The backplane (motherboard) in the PSM subrack provides pins for the shared resource bus toconnect the bus with the boards.

Realization

As shown in Figure 2-3, each subrack has two shared resource buses, namely A and B. Thebandwidth of each shared resource bus is 2 Gbit/s.

Figure 2-3 Shared resource bus

UACU

UBIU

UACU

UBIU

URCU

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

URCU

Shared resource bus BShared resource bus A

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Slot

FB: front board

The URCU at slot 6 manages the front boards configured in the left half of the subrack throughshared resource bus A. The URCU at slot 8 manages the front boards (except the UALU andUPWR) configured in the right half of the subrack through shared resource bus B.

The UACUs at slots 7 and 9 are respectively connected to the two shared resource buses to bridgethe two buses. In this case, the URCU at slot 6 can manage the front boards (except the UALUand UPWR) configured in the right half of the subrack through shared resource bus B, and theURCU at slot 8 can manage the front boards configured in the left half of the subrack throughshared resource bus A.

The URCUs adopt the active and standby working mode. The active URCU manages the frontboards (except the UALU and UPWR) in the whole subrack through shared resource bus A andshared resource bus B.

2.2.2 H.110 BusThe H.110 bus provides the following functions: Carrying out service switchover between theactive and standby USPUs or UGBIs. Providing a transmission channel for reference clock inthe subrack


System Principle


Issue 03 (2009-05-27)

FunctionsAs shown in Figure 2-4, each subrack has one H.110 bus, which provides a switching capacityof 4,096 timeslots and bandwidth of 256 Mbit/s. The H.110 bus provides the following functions:

l Carrying out service switchover between the active and standby USPUs or UGBIs.

l Providing a transmission channel for reference clock in the subrack.

Figure 2-4 H.110 bus

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

UACU

UBIU

UACU

UBIU

URCU

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

FB

URCU

H.110 bus

BB: backboard

FB: frontboard

Service Backup for Front Board SwitchoverNOTE

This section takes the USPU switchover as an example. The switchover procedure for the UGBI is similarto that for the USPU.

As shown in Figure 2-5, the communication path for narrowband SS7 is from E1, UEPI 0,internal highway bus, and to USPU0.

When the USPU is switched over, the communication path is from E1, UEPI 0, H.110 bus, UEPI1, internal highway bus, and to USPU0.

NOTE

The highway bus is used to transfer data between the front board and its back board. The transfer rate is 8Mbit/s. Two channels of highway buses correspond to eight channels of E1 in the back board.



2-5

Figure 2-5 Principle of the USPU switchover

UEPI0

USPU0

UEPI1

USPU1

H.110 bus

UEPI0

USPU0

UEPI1

USPU1

H.110 bus

Data Data

Beforeswitchover

Afterswitchover

HWHW HW HW

CAUTIONOnly in the case of front board switchover, H.110 bus can carry out service backup. Because E1is fixedly configured in the UEPI, the signaling link may be interrupted if the back board isswitched over.

2.2.3 Serial Port BusThe serial port bus carries out control, load, and state query for the boards that are controlled bythe center processing unit (CPU) in the subrack but not connected to the shared resource bus.These boards include the UCKI, UEPI, and UALU.

As shown in Figure 2-6, the rate of the serial port bus is 9,600 bit/s. The URCU is an activenode. The UCKI, UEPI, and UALU are standby nodes.


System Principle


Issue 03 (2009-05-27)

Figure 2-6 Serial port bus

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

BB

UACU

UBIU

UACU

UBIU

URCU

URCU

UALU

Serial port bus

BB: back board

NOTE

The standby node of the serial ports also includes the power distribution box. It communicates with theactive node at the rate of 9,600 bit/s.

2.3 Power Supply SubSystemThe power supply subsystem powers the entire SGSN9810. It requires high reliability. TheSGSN9810 adopts a dual-circuit backup and point-to-point monitoring method in the design.

2.3.1 StructureThe power supply system consists of two parts:Power input part and Power distribution part

2.3.2 Power Supply MonitoringThe power supply monitoring module monitors the power supply system in real time, reportspower running status, and generates alarms when detecting faults.

2.3.1 StructureThe power supply system consists of two parts:Power input part and Power distribution part

Power Input PartThe power input part refers to the power distribution frame (PDF) from the direct current (DC)distributor to the SGSN9810 cabinet.




2-7

Figure 2-7 Power input part

-48V2

GND

PGND

-48V1 PG

ND

-48V1

-48V2

BG

ND

GND

PG

ND

-48V1

-48V2

BG

ND

PG

ND

-48V1

-48V2

BG

ND

(1)

(2)

(3) (3) (3)

(4)

(1) DC distributor (2) Power distribution frame

(3) SGSN9810 cabinet (4) Protection grounding bus

The power input part contains the DC distributor, the PDF, and the connection cables.

The DC distributor and the power distribution cabinet are not parts of the SGSN9810. The powerdistribution cabinet is required to provide two independent and stable channels of input powersupply. The DC distributor provides two independent channels of – 48 V power supply and onechannel of protection ground (PGND) for each SGSN9810 cabinet.

Normally, two channels of – 48 V power supply work at the same time. When one is faulty, theother independently supplies power.

Power Distribution PartThe power distribution part refers to power distribution from the power distribution box (PDB)to each component of the cabinet.



System Principle


Issue 03 (2009-05-27)

Figure 2-8 Power distribution part

11

12

13

W 9 11 12

9 10

ATM155M

UBIU UBIU

8K_IN8K_OUT

COM1COM2

10/100 BT

6.1 6.2W 8

PSM0

PSM1

W 6W 77.1 7.22.22.1

W 4W 54.1 4.23.13.2

PSM2

W 3 W 25.25.1 8.1 8.2

PSM3

3.1 3.2 4.1 4.2

1.1 1.2 2.1 2.2 5.1 5.2 6.1 6.2 7.1 7.2 8.1 8.2

-48V1 RTN1 -48V2 RTN2 -48V3 RTN3 -48V4 RTN4 RTN5 RTN6-48V6-48V5

QW11WSTB

COM1COM2

QW11WSTB

9

10

COM2 +

W 1

Table 2-1 lists the cable numbers and cable names in Figure 2-8.



2-9

Table 2-1 Connection description in the PSM subrack

Cable Name Cable Number

PSM0 subrack power cable 1 and 6




PDB monitor cable 9 and 10

Subrack PGND cable From W2 to W9

Inter-cabinet PGND cable From 11 to 13

Two channels of – 48 V power supply are input into a power distribution box (PDB) afterlightning protection and overcurrent protection. Then eight channels of – 48 V power supply intwo groups (four channels in each group) are distributed to the subracks in the cabinet. The twogroups work as hot backup for each other.

The UPWR in each subrack obtains – 48 V power from the backplane. The power is then providedfor other boards after converted to the working power.

Meanwhile, the PDB checks the input power voltage and output power state. It generates anaudio alarm when a fault occurs.

2.3.2 Power Supply MonitoringThe power supply monitoring module monitors the power supply system in real time, reportspower running status, and generates alarms when detecting faults.

Monitoring the PDBEach cabinet of the SGSN9810 is configured with a PDB, which is monitored by the serviceprocessing subrack.

Figure 2-9 shows the principles of monitoring the PDB.

Figure 2-9 Principles of monitoring the PDB

URCU

Monitor board

PDB

UBIU

URCU

UBIU

RS485RS485


System Principle


Issue 03 (2009-05-27)

The principles of monitoring the PDB are illustrated as follows:

l The PDB is equipped with a monitor board, which is used to collect the running status ofthe PDB.

l The monitor board provides two RS485 serial ports, one active and the other standby.Through the RS485 serial port cables, the active port connects with the COM2+ interfaceon the UBIU, back board of the active URCU and the standby port connects with the COM2+ interface on the UBIU, back board of the standby URCU.

l The URCU processes the information collected from the PDB and reports the results to theUOMU. When a fault occurs, the URCU generates an alarm and sends it to the alarmsubsystem and alarm box.

NOTE

When a cabinet is configured with multiple service processing subracks, the lowest subrack installed inthe cabinet monitors the PDB of the cabinet.

Monitoring Power Supply of Service Processing Subracks

The UPWR is the power supply module in the service processing subrack. It monitors the UPWRthrough the UALU of the subrack.

Figure 2-10 shows the principles of monitoring the UPWR.

Figure 2-10 Principles of monitoring the UPWR

UALU

UPWR

UPWR

UPWR

UPWR

WSMU

URCU

Powerstate signal

Each service processing subrack is configured with four UPWRs, two at the front and two at therear. The principles of monitoring the UPWR are illustrated as follows:

l The UPWR reports the power supply status to the UALU through the dedicated signalcables in the backplane.

l The UALU monitors the power supply status in real time. It reports the status data to theURCU. The UALU also displays the status of the back UPWRs through the indicators.

l The URCU processes the data reported by the UALU, and sends the results to the UOMU.If the power supply system is faulty, the URCU sends an alarm to the alarm box and alarmsubsystem through the UOMU.

l The UALU has a temperature sensor to monitor the temperature of the subrack.



2-11

2.4 Clock Synchronization SubsystemWhen the SGSN9810 provides narrowband signaling to connect with other devices or framerelay (FR) to connect with the base station subsystem (BSS), the clock synchronizationsubsystem is required to be configured to carry out clock synchronization.

The clock synchronization subsystem of the SGSN9810 adopts advanced digital phase-lock loopand reliable software phase-lock technologies. It has the following features:

l The subsystem enables stratum-2 clock (including category A and category B), stratum-3clock, and enhanced stratum-3 clock for choice.

l The structure can be flexibly customized. The stratum-2 and stratum-3 clocks can beselected through terminals.

l The input reference source is diversified, such as 2.048 MHz and 2.048 Mbit/s.

l The software has powerful functions, such as display, alarm, and O&M functions. You canuse the maintenance terminal to control the reference clock and phase-lock mode.

l The subsystem has powerful phase-lock capability, and is applicable to different clocktransmission conditions. When the clock reference subsystem is abnormal, the clocksynchronization subsystem can work in free-run mode to maintain synchronization for aperiod of time.

2.4.1 Technical SpecificationsTechnical specifications consists of Network access parameter, Long-term phase change, Clockworking mode, Input jitter tolerance.

2.4.2 StructureThe UCKI is the core of the whole clock synchronization system. It is fixedly configured in thebasic subrack. The active and standby UCKIs work in the hot backup mode.

2.4.3 Clock Interface PartThe clock interface part includes the UCKI, UEPI/UTPI, and UPIU boards in addition toconnected cables. It accesses and locks the clock source to provide the stable clock for theSGSN9810.

2.4.4 Clock Distribution PartThe clock distribution part includes the UCKI, UBIU, UPIU, dedicated clock cables, and H.110bus. The clock distribution part distributes the clock signals provided by the UCKI to the UEPIsor UPIUs in all the subracks.

2.4.5 Clock Control PartThe clock control part includes the URCU, UOMU, local maintenance terminal (LMT), andserial port bus.

2.4.1 Technical SpecificationsTechnical specifications consists of Network access parameter, Long-term phase change, Clockworking mode, Input jitter tolerance.

Table 2-2 shows the technical specifications of the clock synchronization system.


System Principle


Issue 03 (2009-05-27)

Table 2-2 Technical specifications of the clock synchronization system

Item Specification

Network accessparameter

Lowest accuracy Stratum-2 clock: ±4×10-7

Stratum-3 clock: ±4.6× 10-6

Pull-in range Stratum-2 clock: able tosynchronize with the accuracy of±4×10-7

Stratum-3 clock: able tosynchronize with the accuracy of±4.6×10-6

Maximum frequency offset Stratum-2 clock: 5×10-10/day

Stratum-3 clock: 2×10-4/day

Initial maximum frequency offset Stratum-2 clock: < 5× 10-10/day

Stratum-3 clock: < 1× 10-8/day

Long-term phasechange

Ideal working status Maximum relative time intervalerror (MRTIE)≤1ms

Hold working status MRTIE (ns)≤a×s +(1/2)×b×s²+cThe letter s indicates time withthe unit as second. The unit ofMRTIE is nanosecond (ns).Stratum-2 clock:

a = 0.5 b = 1.16×10-5 c = 1000Stratum-3 clock:

a = 10 b = 2.3×10-4 c = 1000

Clock workingmode

Fast pull-in, locked, holdover, and free-run

Input jitter tolerance Refer to Figure 2-11 for details.

NOTE

l Lowest accuracy is the maximum value of the offset to the nominal frequency in a long term (20 years)in the case of no external reference frequency (free-run mode).

l Maximum frequency offset is the maximum value of the relative frequency offset in a unit period duringthe consecutive running of the clock.

l Pull-in range is the maximum frequency bandwidth of the input clock signals that the clock can lock.

l MRTIE refers to the maximum peak-peak delay change of the tested clock to an actual reference clockduring the test.



2-13

Figure 2-11 Maximum allowed input jitter and lower limit of wander

Y (UI)

10 2

X

A0 =36.9

10 1

A1=1.5

A2=0.2

1.2 ´ 10-5

1

10 20 2.4 k 18 k 100 k f (Hz)

10 -1

Peak-to-peak jitter and wander amplitude (logarithm)

Slope: 20dB / 10 times of frequency interval

For example, if the jitter frequency of an input signal is 1 kHz, the amplitude is greater than 1.5UI, and the system can still work normally, it indicates that the signal meets the requirements.

NOTE

UI is the unit interval. The reciprocal of the digital signal frequency is one UI. For example, the UI of 2.048Mbit/s signal is 488 ns.

2.4.2 StructureThe UCKI is the core of the whole clock synchronization system. It is fixedly configured in thebasic subrack. The active and standby UCKIs work in the hot backup mode.

Figure 2-12 shows the architecture of the clock synchronization system.


System Principle


Issue 03 (2009-05-27)

Figure 2-12 Architecture of the clock synchronization system

UEPI

UPIU

UBIU

UCKI

UBIU

UPIU

UBIU

UEPI

UPIU

UGFU

UFCU

Switchingsubrack

8 kHz internalclock cable

2 MHz internalclock cable

STM-1 H.110 bus

E1STM-1/STM-4

UGFU

E1 STM-1/STM-4

BITS

URCU

URCU

USPU

UEPI

UGBI

USPU

URCU U

BIU

UEPI

UPIU

UGFU

H.110 bus

E1 STM-1/STM-4

URCU

USPU

UEPI

UGBI

STM-1H.110 bus

The clock synchronization system of the SGSN9810 consists of three parts:

l Clock interface partl Clock signaling distribution partl Clock control part

The UCKI is the core of the whole clock synchronization system. It is fixedly configured in thebasic subrack. The active and standby UCKIs work in the hot backup mode.

2.4.3 Clock Interface PartThe clock interface part includes the UCKI, UEPI/UTPI, and UPIU boards in addition toconnected cables. It accesses and locks the clock source to provide the stable clock for theSGSN9810.

The SGSN9810 supports two types of clock sources, cable clock source and building integratedtiming supply (BITS) clock source. If the clock source is stratum 2, the local clock can be set tostratum 2 or stratum 3. If the clock source is stratum 3, the local clock can be set to only stratum3.

l Cable clock sourceIf the clock stratum of the peer device (HLR) is lower than stratum 3, the local end canextract the clock source from the E1 or SDH that is connected with the peer end.



2-15

– The UEPI provides the E1 interface to extract the E1 cable clock from the peer end andgenerate a 2 MHz clock source.

– The UPIU provides the SDH interface for ATM-1 or ATM-4 to extract the SDH cableclock and generate a 2 MHz clock source. The extracted 2 MHz clock is sent to theUBIU through the local bus. Then the UBIU provides the clock interface for the clockto access the UCKI.

– The UCKI obtains the cable clock from the UEPI or UBIU through the 2 MHz internalclock cable.

– The UCKI traces, locks, and generates the cable clock and then generates stable clocksignals.

l BITS clock sourceThe interfaces provided by the UCKI can directly connect with the external clock source,such as BITS. Thus, the UCKI can obtain the 2 MHz or 2 Mbit/s clock source.

2.4.4 Clock Distribution PartThe clock distribution part includes the UCKI, UBIU, UPIU, dedicated clock cables, and H.110bus. The clock distribution part distributes the clock signals provided by the UCKI to the UEPIsor UPIUs in all the subracks.

The clock distribution part includes clock distribution from the UCKI to all the PSM subracksand clock distribution inside the PSM subrack.

Clock Distribution from the UCKI to all the PSM SubracksThe steps for distributing signals from the UCKI to all the PSM subracks are as follows:

1. The UCKI sends the clock signals to the UBIU through the 8 kHz internal clock cable.2. The UBIU sends the clock signals to the UPIU, back board of the UFCU through the H.

110 clock bus.3. The UPIU, back board of the UFCU sends the clock signals to the UBIUs in all the subracks.

Clock Distribution Inside the PSM SubrackFigure 2-13 shows the procedure for clock distribution inside the PSM subrack.


System Principle


Issue 03 (2009-05-27)

Figure 2-13 Procedure for clock distribution inside the PSM subrack

H.110 clock bus A

UEPI

UBIU

URCU

8 kHz clock ref. cable

H.110 clock bus B

UEPI

UEPI

UBIU

URCU

UPIU

8 kHz clock ref. cable

UPIU

UPIU

The steps for distributing clock signals inside the PSM subrack are as follows:

1. The UBIU sends the STM-1 signals to the URCU.2. The UPIU, subboard of the URCU processes the STM-1 signals and extracts the clock

signals that are then sent to the UBIU.

NOTE

The UBIU in the switching subrack directly obtains the clock signals from the UCKI through the 8kHz internal clock cable. Therefore, the UBIU does not need to obtain the clock signals from theURCU.

3. After receiving the clock signals, the UBIU carries out either the following settings basedon data configuration and the DIP switches:l Directly driving the H.110 bus in the PSM subrack

l Sending the clock signals to the UEPI through the 8 kHz internal clock cable. The H.110 bus is driven by the UEPI.

4. The UPIU, subboard of the UEPI and UGFU, extracts the clock signals from the H.110bus.

The H.110 bus consists of the following two groups:

l CLK_A: driven by the UBIU in slot 6 or the UEPI configured for the primary master (PM).



2-17

l CLK_B: driven by the UBIU in slot 8 or the UEPI configured for the secondary master(SM).

For normal operation, CLK_A provides the clock. For abnormal operation, CLK_B providesthe clock.

2.4.5 Clock Control PartThe clock control part includes the URCU, UOMU, local maintenance terminal (LMT), andserial port bus.

Through the clock control module, you can carry out data configuration, data maintenance, andstatus query for the SGSN9810 clock system.

2.5 Equipment Monitoring SubsystemThe equipment monitoring subsystem consists of fan monitoring and equipment roomenvironment monitoring to ensure that the SGSN can work in a normal environment.

2.5.1 Fan MonitoringEach PSM subrack is equipped with a fan box. The fan box contains six fans and a fan monitoringmodule. Based on the temperature of the subrack, the fan monitoring module monitors therunning status of the fan and adjusts the rotation speed.

2.5.2 Equipment Room Environment MonitoringThe PDB monitors the environment of the equipment room. Equipment room environmentmonitoring is an optional function.

2.5.1 Fan MonitoringEach PSM subrack is equipped with a fan box. The fan box contains six fans and a fan monitoringmodule. Based on the temperature of the subrack, the fan monitoring module monitors therunning status of the fan and adjusts the rotation speed.

Figure 2-14 shows the architecture of the fan monitoring module.

Figure 2-14 Fan monitoring

PSM subrack

Monitorboard

WSMU

URCU

Fan

Fan

Fan

Fan

Fan

Fan

Fan box

The principles of fan monitoring are illustrated as follows:


System Principle


Issue 03 (2009-05-27)

l The fan box is equipped with a monitor board, which is used to collect the running statusof the fan box.

l The monitor board provides an RS485 serial port to connect to the UBIU, backboard of theURCU in the service processing subrack through a RS485 serial port cable on the backplaneof the subrack.

l The URCU analyzes the information collected from the fan box and reports the results tothe UOMU. For the detected faults, the URCU sends alarms to the alarm subsystem andalarm box through the UOMU.

l You can configure the fan box through the maintenance system.

2.5.2 Equipment Room Environment MonitoringThe PDB monitors the environment of the equipment room. Equipment room environmentmonitoring is an optional function.

Figure 2-15 shows the principle of the equipment room environment monitoring.

Figure 2-15 Equipment room environment monitoring

URCU

Monitor board

PSM subrack

PDB

UBIU

URCU

UBIU

RS485RS485

Detectioninterfaces

Connectedto sensors

The PDB has five Boolean value detection interfaces which are connected to the temperaturesensor, the humidity sensor, and the smoke sensor.

The reporting path of the equipment room is the same as that of the PDB power status.



2-19

3 Principle of the Platform System

About This Chapter


3.1 The location of the platform systemAll the software of the SGSN boards contains the platform system.

3.2 Platform Management SubsystemThe platform management subsystem realizes operation system, hardware drive, andcommunications between boards. It is the foundation on which other software modules operate.The platform management subsystem works in all the boards.

3.3 Internal Communication SubsystemThe hardware of the SGSN consists of multiple subracks. Different subracks need exchangeinformation, such as signaling and data, with each other. The internal communication subsystemrealizes information exchange between the different subracks.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 3 Principle of the Platform System


3-1

3.1 The location of the platform systemAll the software of the SGSN boards contains the platform system.


Figure 3-1 shows the location of the platform system in the SGSN.

Figure 3-1 Location of the platform system in the SGSN

BSS

UICP

Platformmanagement

OM

Gbinterface

subsystem

Platformmanagement

OM

UGBI

Signalingsubsystem

Platformmanagement

OM

USIG

Signalingsubsystem

Platform management

OM

Chargingsystem

USPUUGTP

Platform management

OM

Chargingsystem

URCU

Platform management

OM


subsystem

UFCU


subsystem

Platformmanagement

OM

UGFU

IP routingsubsystem

Platformmanagement

OM

Gn/Gpinterface

subsystem

UOMU

Platformmanagement

OM

UCDR

Chargingsystem

Platformmanagement

OM

BSS

No.7signalling

node, suchas HLR


LMT

BUS

BUS

Service subrack

Switching subrack


subsystem

Gn/Gpinterface

subsystem

E1 E1


Fiber cable

Fiber cable


3 Principle of the Platform SystemHUAWEI SGSN9810 Serving GPRS Support Node

System Principle


Issue 03 (2009-05-27)

3.2 Platform Management SubsystemThe platform management subsystem realizes operation system, hardware drive, andcommunications between boards. It is the foundation on which other software modules operate.The platform management subsystem works in all the boards.

3.2.1 The Structure of Platform Management SubsystemThe platform management subsystem consists of the following modules: Operation systemmodule, Data management module, Load management module, Switchover and backupmanagement module.

3.2.2 Load ManagementLoad means a process of loading software to the Flash memory of a board. The boards in thePSM subrack can work only after the software is loaded.

3.2.3 Startup ManagementBoard startup means a process from board power-on till the board is in normal operation. Duringthis process, the board completes:

3.2.4 Switchover ManagementThe purpose of switchover is to enhance stability for system operation. Once a board runsabnormally, the system can activate the backup board to replace the work done by the faultyboard in case of service interruption.

3.2.5 Patch ProcessingSometimes adaptive and corrective modifications to the host software are required during therunning of a system. For example, you need to eliminate some found defects from the system,and add some new features. Traditionally, you halt the running of the host software to upgrade.It affects services, however, and is not beneficial to enhance communication quality. By patchingthe host software, the software can be upgraded in the in-service state, which ensures the qualityof the provided communication services.

3.2.1 The Structure of Platform Management SubsystemThe platform management subsystem consists of the following modules: Operation systemmodule, Data management module, Load management module, Switchover and backupmanagement module.

Figure 3-2 shows the modules inside the platform management subsystem.

Figure 3-2 Modules inside the platform management subsystem

Datamanagement

Loadmanagement

Operation system

Switchover andbackup

management



3-3

The platform management subsystem consists of the following modules:

l Operation system module: it realizes hardware drive, communications management, andmemory management

l Data management module: it realizes configuration data and user data management

l Load management module: it realizes software and patch load management

l Switchover and backup management module: it realizes board switchover and backupcontrol

3.2.2 Load ManagementLoad means a process of loading software to the Flash memory of a board. The boards in thePSM subrack can work only after the software is loaded.

Overview of Load ManagementLoad can apply to the whole system, whole subrack, all versions, whole board, a file, or a patch.

Load means a process of loading software to the Flash memory of a board. The boards in thePSM subrack can work only after the software is loaded. Load can apply to the whole system,whole subrack, all versions, whole board, a file, or a patch.

The loaded data includes load module, product basic input output system (BIOS), host software,and patch.

The SGSN9810 has the following two board software versions:

l Active versionIt is saved in directory \hda0\sgsn\software in the hard disk of the UOMU.

l Backup versionIt is saved in directory \hda0\sgsn\softback in the hard disk of the UOMU.

Principle of Load ManagementDifferent boards have different loading channels.

Figure 3-3 shows the loading channels for each board.


System Principle


Issue 03 (2009-05-27)

Figure 3-3 Loading channels for each board

UGFU/UGPUUFCU

Active URCU

Active UOMU

UCDR/StandbyUOMU

UGFU/UGPU

ULAN

Switching subrack

Servicing subrack

(1)

(5)

(6)

(4)

UPIU

(2) (3) (2)

UEPI/UPIU

(7)

(8)

Standby URCU

Active URCUStandby URCU

NOTE

In Figure 3-3, the UGPU represents the UGBI, USPU, UICP, UGTP, and USIG.

The steps for loading the software for each board are as follows:

l Path 1:For the URCU in the switching subrack: the active packet UOMU → the URCU in theswitching subrack– The active URCU in the switching subrack loads the host software from the active

UOMU through an Ethernet cable.– The standby URCU in the switching subrack loads the host software from the active

UOMU through an optical fiber. If the load fails, the standby URCU in the switchingsubrack loads the host software from the active UOMU through an Ethernet cable.

l Path 2:The UGPU/UFCU/UGFU in the switching subrack: the active UOMU → the URCU in theswitching subrack → the UGPU/UFCU/UGFU in the switching subrackThe UGPU/UFCU/UGFU in the switching subrack loads the host software from the activeURCU through the resource Bus.

l Path 3:The UPIU in the switching subrack: the active UOMU → the URCU in the switchingsubrack → the UPIU in the switching subrack



3-5

The UPIU in the switching subrack loads the host software from the active URCU throughthe port Bus.

l Path 4:The ULAN: the active UOMU → the ULANThe ULAN loads the host software from the active UOMU through an Ethernet cable.

l Path 5:The URCU in the service subrack: the active UOMU → the UFCU → the URCU in theservice subrack

l Path 6:The UGPU/UGFU in the service subrack except the UOMU and UCDR: the active UOMU→ the UFCU → the URCU in the service subrack → the UGPU/UGFU in the servicesubrack

l Path 7:The UEPI/UPIU in the service subrack : the active UOMU → the UFCU → the URCU inthe service subrack → the UEPI/UPIU in the service subrackThe UEPI/UPIU in the service subrack loads the host software from the active URCUthrough the port Bus.

l Path 8:UCDR/standby UOMU: the active UOMU → the UFCU → the UCDR/standby UOMU

NOTE

l The active and standby UOMUs connect to different UFCUs.

l The back boards except the ULAN load the host software through their front boards.

l The subboard loads the host software through its front board and back board.

3.2.3 Startup ManagementBoard startup means a process from board power-on till the board is in normal operation. Duringthis process, the board completes:l Initializing the software and hardware

l Obtaining and processing the configuration data for the board

Figure 3-4 shows the sequence of SGSN9810 board startup.


System Principle


Issue 03 (2009-05-27)

Figure 3-4 Sequence of board startup

Backplane busActive URCU in theswitching subrack

Active UOMU

Active and standbyUFCU/UGFU/UGPU in the

switching subrack

Standby UOMUActive and standby

URCU in the servicesubrack

Standby URCU inthe switching

subrack

Active and standbyUGFU/UGPU in the service subrack

Backplane bus

Ethernet channelSTM-1

STM-1

STM-1

STM-1

Start sequence 4

Start sequence 3

Start sequence 2

Start sequence 1

The steps for the board startup are as follows:

1. The active UOMU starts.

2. The active URCU in the switching subrack requests startup to the active UOMU.

3. The active and standby UFCUs/UGFUs/UGPUs in the switching subrack request startupto the active URCU in the switching subrack.

4. The active/standby URCUs and UCDRs in the service subrack, the standby URCU in theswitching subrack, and the standby UOMU request startup to the active URCU in theswitching subrack through STM-1 multimode optical fibers.

5. The UGFU/UGPU in the service subrack requests startup to the URCU in the servicesubrack through the backplane bus.

NOTE

l Hereinbefore descriptions refer to UOMU offline startup and boards startup. The other one mode isUOMU online startup, here URCU is normal working, when the maim UOMU be reset and restarts, itshould send request to main URCU and then be restarted.

l If an error occurs during the UOMU startup caused by the configuration data in mml.txt, the UOMUsends the error of the wrong data configuration to the FTP server. Therefore, the FTP server must beensured for normal operation and correct configuration during the process of startup.

l The standby UOMU, standby UCDR, URCU in the switching subrack, and the URCU in the non-switching subrack cannot start working until the UFCU/ UPIU works normally.

3.2.4 Switchover ManagementThe purpose of switchover is to enhance stability for system operation. Once a board runsabnormally, the system can activate the backup board to replace the work done by the faultyboard in case of service interruption.



3-7

Overview of Switchover ManagementBoard switchover is triggered by various factors under a specified prerequisite.

The purpose of switchover is to enhance stability for system operation. Once a board runsabnormally, the system can activate the backup board to replace the work done by the faultyboard in case of service interruption.

The prerequisite for switchover is that a backup board exists. The boards in the SGSN have thefollowing two backup types:

l 1+1 backup: suitable for a majority of the boards

l N+1 backup: suitable for the UGBI board

Switchover consists of the following three types:

l Fault switchoverTriggered by faulty reset of a board

l Manual switchoverTriggered by a manual command

l Automatic manual switchoverTriggered by a hot board swap, a back board fault, and the UGBI switchover

Principle of Switchover ManagementThe switchover procedure contains the following four steps: switchover judgment beforehand,earlier stage of upper-layer switchover, lower-layer switchover, and later stage of upper-layerswitchover.

Figure 3-5 shows the switchover procedure.

Figure 3-5 Switchover procedure

Switchover judgmentbeforehand

Earlier stage of upper-layer switchover

Low-layer switchover Low-layer switchover

Later stage of upper-layer switchover

Old active board New active board

Switchover judgmentbeforehandStep 1

Step 2

Step 3

Step 4

Step 1

Step 3

The switchover procedure contains the following four steps:

1. Switchover judgment beforehandThis step is to judge whether the switchover conditions are met and whether the switchovercan be carried out. The upper-layer modules can add the restrictions on manual switchoverin this step, such as restricting manual switchover when the data for the active and standbyboards is inconsistent.


System Principle


Issue 03 (2009-05-27)

NOTE

Only manual switchover has this step

2. Earlier stage of upper-layer switchover

This step is the earlier stage of the switchover. The upper-layer modules in the originalactive board make preparations for the switchover, such as backing up the data that has notbeen backed up to the standby board. After the switchover, the original active board isresetted.

NOTE

Only manual switchover has this step.

3. Low-layer switchover

This step is to finish switchover of the operational system (OS) in the lower-layer modules,synchronization of internal communication links, and central database (CDB) data switch.

4. Later stage of upper-layer switchover

This step is the later stage of the switchover. The upper-layer modules in the new activeboard carry out some smooth work to ensure normal services, such as data consistencycheck. After the switchover, the new active board can perform the services.

If the manual switchover fails in the earlier stage of upper-layer switchover, switchover recoveryis needed. If it fails in the late stage of upper-layer switchover, however, switchover recoveryis not needed.

When the earlier stage of upper-layer switchover fails, the original active board still runsnormally but the standby board is resetted. The upper-layer modules in the original active boardroll back the work carried out in this stage.

3.2.5 Patch ProcessingSometimes adaptive and corrective modifications to the host software are required during therunning of a system. For example, you need to eliminate some found defects from the system,and add some new features. Traditionally, you halt the running of the host software to upgrade.It affects services, however, and is not beneficial to enhance communication quality. By patchingthe host software, the software can be upgraded in the in-service state, which ensures the qualityof the provided communication services.

Concept of Patch

The fundamental concepts of the software paten are described as follows: Patch, Patch area,Patch file, Patch unit, Patch ID.

Sometimes adaptive and corrective modifications to the host software are required during therunning of a system. For example, you need to eliminate some found defects from the system,and add some new features. Traditionally, you halt the running of the host software to upgrade.It affects services, however, and is not beneficial to enhance communication quality. By patchingthe host software, the software can be upgraded in the in-service state, which ensures the qualityof the provided communication services.

Before the patch is activated, the function call statements of the main program calls the faultyfunction. After the patch is activated, however, the function call statements of the main programare modified to the correct function in the patch area, and thus the function problem is solved.



3-9

Principle of Patch managementSoftware patch management includes load, activation, deactivation, confirmation, and removalto realize state transfer for a patch.

Figure 3-6 shows the working principle of the software patch.

Figure 3-6 Working principle of the software patch

Function1 (correct)

Patch area

Program area

Function1 (faulty)

Call function1

Function2 (faulty) Call function2 Function2 (correct)

Function3 (faulty)

Call function3

Beforeactivation

Afteractivation

Main program

Patch unit 1

Function3 (correct) Patch unit 2

NOTE

The function call statements of the main program are modified in the system memory after the patchactivation command is executed. For the confirmed patch, the function call statements are automaticallymodified after the board resets. For the unconfirmed patch, however, the original function call statementsare used.

The fundamental concepts of the software patch are described as follows:

l PatchA patch is a segment of executable program codes, used to replace the codes to be correctedor updated in the host software.

l Patch areaThe patch area is a dedicated area in the memory of the SGSN used to store patches.

l Patch fileA patch file is a dedicated file that contains patch information. A patch file may containmultiple patch units. The UOMU can save multiple patch files, but only one activated patchfile can be loaded to the patch area of a board.

l Patch unitA patch unit is added to the patch file by every time patching the host software. The newpatch file differs from the old one in an additional patch unit. A patch unit may containmodification to multiple functions. The patch discussed in this document specially meansthe patch unit. Patch management is actually management on patch units.

l Patch IDThe patch ID an identifier used to mark the patch unit in the form of character string, suchas "CUOMU001." This character string contains three parts: C/T, board type, and patchunit ID. Letter C indicates that the patch is commercial and letter D indicates that the patchis temporary. The patch unit ID is a digit.


System Principle


Issue 03 (2009-05-27)

A patch has four states in the host software:

l Idle state: The initial state which indicates that the memory does not contain the softwarepatch.

l Deactivated state: The patch is in the patch area but is not activated. The patch codes cannotbe executed.

l Activated state: The patch is activated. The patch codes can be executed. This is a pilotstate.

l Operating state: The patch is in the normal working state. It cannot be deactivated, but onlyremoved.

Software patch management includes load, activation, deactivation, confirmation, and removalto realize state transfer for a patch, as shown in Figure 3-7.

Figure 3-7 Transfer of patch states

Idle state Deactivated state

Operating state Activated state

Load

Remove

RemoveRemove

Confirm

Activate Deactivate

3.3 Internal Communication SubsystemThe hardware of the SGSN consists of multiple subracks. Different subracks need exchangeinformation, such as signaling and data, with each other. The internal communication subsystemrealizes information exchange between the different subracks.

3.3.1 StructureThe internal communication subsystem consists of the exchange processing module and theexchange controlling module.

3.3.2 The procedure for exchanging data between the subracksThe UFCU need cooperate with the URCU to exchange data between the subracks.

3.3.1 StructureThe internal communication subsystem consists of the exchange processing module and theexchange controlling module.

Figure 3-8 shows the logical structure of the internal communication subsystem.



3-11

Figure 3-8 Logical structure of the internal communication subsystem

UPIU

Exchangeprocessing

Exchangecontrolling

UFCU

The internal communication subsystem works in the UFCU. The subsystem consists of thefollowing modules:

l Exchange processing module: encapsulating and forwarding data between the subracks

l Exchange controlling module: managing and maintaining routing data between thesubracks

3.3.2 The procedure for exchanging data between the subracksThe UFCU need cooperate with the URCU to exchange data between the subracks.

Figure 3-9 shows the procedure for exchanging data between the subracks.


System Principle


Issue 03 (2009-05-27)

Figure 3-9 Procedure for exchanging data between the subracks

Serviceboard

URCUBus

UFCUATM STM-1

UFCU

Serviceboard

URCU

Destination subrackNo./slot No.

Data Destination subrackNo./slot No.

Data

VPI/VCI

Destination subrackNo./slot No.

Data

VPI/VCI

Destination subrack No./slot No.

Data

Bus ATM STM-1

Bus

The steps for exchanging data between the subracks are as follows:

1. The service board adds the destination subrack number and slot number in the message thatis then sent to the URCU through the local bus.

2. The URCU adds the VPI and VCI in the message, and disassembles the message to ATMcells. Then the ATM cells are sent to the switching subrack through the fibers connectingthe subracks.

3. The source UFCU combines the data from the ATM cells into the destination data. Basedon the destination subrack number, the source UFCU determines the UFCU connected withthe destination subrack. Then the data is forwarded to the destination UFCU through thelocal bus.

4. The destination UFCU encapsulates the message to the ATM cells and adds the VPI andVCI for addressing. Then the UFCU sends the message to the destination URCU.

5. The destination URCU obtains the destination slot number from the payload in the ATMcells and then sends the message containing the slot number to the destination service boardthrough the local bus.



3-13

4 Principle of the Service System

About This Chapter


4.1 The structure of the service processing systemThe UICP, UGTP, USIG, UGBI, USPU, and UGFU boards have the service system.

4.2 IP Routing SubsystemThe IP routing subsystem provides the interfaces to connect the SGSN with the external IPnetworks and realizes communication with the GSN, CG, DNS server, NTP server, RNC, SS7node supporting SS7 over IP, and PCU supporting Gb over IP.

4.3 Gb Interface SubsystemThe Gb interface subsystem realizes the functions of the FR layer, NS layer, BSSGP layer, LLClayer, and SNDCP for the Gb interface.

4.4 Iu Interface Control Plane SubsystemThe Iu interface control plane subsystem realizes the functions of the SAAL, MTP3B, SCCP,and RANAP layers for the Iu interface control plane.

4.5 Gn/Gp Interface SubsystemThe Gn/Gp interface subsystem realizes the following functions:GTP-C signalingforwarding,NTP client,DNS client,GTP data packets forwarding between the Gn/Gp interfaceand Iu interface or between the Gn/Gp interface and Gb interface

4.6 Signaling SubsystemThe signaling subsystem realizes the functions of MTP L1/L2/L3, or SCTP and M3UA ofSIGTRAN for SS7 in addition to SCCP, MAP, TCAP, CAP, MM, SM, SMS, CAMEL, andBSSAP+ protocol layers.

4.7 Typical Data Processing ProcedureThe procedure for handling the typical data contains signaling and data handling.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 4 Principle of the Service System


4-1

4.1 The structure of the service processing systemThe UICP, UGTP, USIG, UGBI, USPU, and UGFU boards have the service system.

Figure 4-1 shows the structure of the service processing system.

Figure 4-1 Structure of the service system

BSS

UICP

Platformmanagement

OM

Gbinterface

subsystem

Platformmanagement

OM

UGBI

Signalingsubsystem

Platformmanagement

OM

USIG

Signalingsubsystem

Platform management

OM

Chargingsystem

USPUUGTP

Platform management

OM

Chargingsystem

URCU

Platform management

OM


subsystem

UFCU


subsystem

Platformmanagement

OM

UGFU

IP routingsubsystem

Platformmanagement

OM

Gn/Gpinterface

subsystem

UOMU

Platformmanagement

OM

UCDR

Chargingsystem

Platformmanagement

OM

BSS

No.7signalling

node, suchas HLR


LMT

BUS

BUS

Service subrack

Switching subrack


subsystem

Gn/Gpinterface

subsystem

E1 E1


Fiber cable

Fiber cable


4 Principle of the Service SystemHUAWEI SGSN9810 Serving GPRS Support Node

System Principle


Issue 03 (2009-05-27)


The functions of the five subsystems are described as follows:

l IP routing subsystemIt provides the interface to connect the SGSN with the external IP network and realizescommunication with the GSN, CG, DNS server, NTP server, RNC, SS7 node supportingSS7 over IP, and PCU supporting Gb over IP.The IP routing subsystem works in the UGFU board.

l Gb interface subsystemIt realizes the functions of the physical, FR, NS, BSSGP, and LLC layers for the Gbinterface.The Gb interface subsystem works in the UGBI board.

l Iu interface control plane subsystemIt realizes the functions of the SAAL, MTP3B, SCCP, and RANAP layers for the Iuinterface control plane.The Iu interface control plane subsystem works in the UICP board.

l Gn/Gp interface subsystemIt processes the Gn/Gp interface protocol and forwards user data between the Gn/Gpinterface and Iu interface or between the Gn/Gp interface and Gb interface.The Gn/Gp interface subsystem works in the UGTP and UGFU boards.

l Signaling subsystemIt realizes the functions of MTP L1/L2/L3, or SCTP and M3UA layers for SS7 in additionto SCCP, MAP, TCAP, CAP, MM, SM, SMS, CAMEL, and BSSAP+ protocol layers.The signaling subsystem works in the USPU and USIG boards. The USIG board realizesthe functions of SCTP, and M3UA layers, and other functions are realized by the USPUboard.

4.2 IP Routing SubsystemThe IP routing subsystem provides the interfaces to connect the SGSN with the external IPnetworks and realizes communication with the GSN, CG, DNS server, NTP server, RNC, SS7node supporting SS7 over IP, and PCU supporting Gb over IP.

4.2.1 The structure of IP Routing SubsystemThe IP routing subsystem consists of the IPv4/IPv6, ACL, TCP, UDP, OSPF, RIP, and routingmodules.

4.2.2 Principle of IP routing subsystem.Routing IP packets is a process in which the SGSN receives the IP packets and then distributesthem to different modules for processing.

4.2.1 The structure of IP Routing SubsystemThe IP routing subsystem consists of the IPv4/IPv6, ACL, TCP, UDP, OSPF, RIP, and routingmodules.



4-3

Figure 4-2 shows the modules inside the IP routing subsystem.

Figure 4-2 Modules inside the IP routing subsystem

RIP

UDP

IPv4

IP routing subsystem

Gn/Gp interface subsystem

TCP OSPF

Platform system

OM system

UGFU

ACL IPv6

Routing module

The modules inside the IP routing subsystem are described as follows:

l IPv4/IPv6

The IPv4 module realizes the functions of the Ipv4 protocol.

The IPv6 module realizes the functions of the Ipv6 protocol that is supported by the Gn/Gp interface, Iu interface, Gb interface, and SS7 interface.

The physical interfaces of the IP network are realized by the UPIU, back board of theUGFU. The types of the physical interfaces are the GE (fiber interface or network interface),FE, STM-1 ATM, and STM-4 ATM interfaces.

l ACL

The access control list (ACL) module filters the IP packets based on the ACL defined bya user to ensure that only the legal data packets can access the SGSN, and therefore preventsthe SGSN from illegal attacks.

l TCP

The TCP module realizes the functions of the TCP protocol that provides reliable datacommunication for the application layer. The TCP module partitions the data received fromthe application into suitable blocks and sends these blocks to the network layer. It alsoconfirms the received packets and sets the time-out clock for the last confirmed packets.


System Principle


Issue 03 (2009-05-27)

NOTE

The SGSN does not use the TCP protocol of the UGFU.

l UDPThe UDP module realizes the functions of the UDP protocol that provides simple servicesfor the application layer. The UDP module sends only the packets called datagram fromone host to another, but it does not ensure that the datagram can reach the other end. Theapplication layer guarantees reliability.

l OSPFThe OSPF module realizes the functions of the Open Shortest Path First (OSPF) protocol.The OSPF protocol is a widely-used Interior Gateway Protocol (IGP) based on link statusdeveloped by the IETF organization.

l RIPThe RIP module realizes the functions of the Routing Information Protocol (RIP). The RIPis a simple IGP mainly used in small-scale networks.

NOTE

The SGSN9810 supports only the RIP and OSPF based on the IPv4 protocol.

l Routing moduleThe routing module maintains the routing table and routes IP packets.All the routing information of the SGSN is saved in the UGFU routing table. Each UGFUmaintains its own routing table. The routing table contains the following information:– Routes to the internal board, such as the UGTP

– Routes between the UGFUs

– Routes to the external devices

– Routes to the destination IP nodes

4.2.2 Principle of IP routing subsystem.Routing IP packets is a process in which the SGSN receives the IP packets and then distributesthem to different modules for processing.

Figure 4-3 shows the procedure for processing IP packets in the IP routing subsystem.



4-5

Figure 4-3 Procedure for processing IP packets in the IP routing subsystem

UPIU

RoutingACL

IPv4/IPv6

TCPUDPOSPF

RIP

Gn/Gp interfacesubsystem

UGFU

UGFU

Router

UGBI

UGTP

UCDR

USIG

Gb interfacedata packets

User planedata RIP routing

information

OSPF routinginformation

Data frame

IP packets

IP packets notprocessed by the

UGFU

UDPpackets

TCPpackets

User planeIP packets

M3UAsignaling

Ga interfacesignaling

Gn/Gp interfacesignaling

IPv4packets

The steps for processing IP packets in the IP routing subsystem are as follows:


System Principle


Issue 03 (2009-05-27)

NOTE

The above figure describes only the processing procedure when the SGSN receives IP packets. Theprocessing procedure when the SGSN sends IP packets is opposite to the procedure when the SGSN receivesIP packets.

1. After receiving the IP packets from the external router, the UPIU board processes the physical layerand link layer and sends the data frames to the UGFU, front board of the UPIU through internal datacables.

2. After the data frames enter the UGFU, they first enter the IPv4/IPv6 module. Then the IPv4/IPv6module carries out the following processing:

l If the ACL function is configured, the ACL module filters the IPv4 packets and then discards theillegal packets.

l If the destination address of the IP packets is not to the UGFU, the IP packets are sent to the routingmodule for forwarding to the specified UGTP, USIG, another UGFU, or UCDR.

l The UGFU decapsulates the IP packets after processing. Based on the protocol types of the packets,the UGFU distributes the packets to the upper-layer modules, such as the OSPF, TCP, or UDP.

3. The IP upper-layer module processes the data packets in the following ways:

l Processed by the UDP module

After receiving the UDP data packets, the UDP module decapsulates the packets and sends the datapackets to the upper layers based on the port numbers. For the GTP packets, the UDP module sendsthem to the Gn/Gp interface subsystem for processing. For the Gb interface data, the UDP modulesends them to the UGBI board for processing. For the RIP data, the UDP module sends them tothe RIP module for processing.

l Processed by the OSPF module

After receiving the routing information, the OSPF module updates the routing table.

4.3 Gb Interface SubsystemThe Gb interface subsystem realizes the functions of the FR layer, NS layer, BSSGP layer, LLClayer, and SNDCP for the Gb interface.

4.3.1 The structure of Gb Interface SubsystemThe Gb interface subsystem works in the UGBI board. When the Gb interface uses IP bearer,the UGFU realizes the IP protocol.

4.3.2 The procedure for processing Gb packets in the Gb interface subsystemHandling Gb-interface messages is a process in which the SGSN receives Gb-interface messagesand then distributes them to the related modules for processing.

4.3.1 The structure of Gb Interface SubsystemThe Gb interface subsystem works in the UGBI board. When the Gb interface uses IP bearer,the UGFU realizes the IP protocol.

Figure 4-4 shows the modules inside the Gb interface subsystem.



4-7

Figure 4-4 Modules inside the Gb interface subsystem

SNDCP

LLC

UEPIFR

UFEU

Encryption/Decryption

UEPCBSSGP

NS

UGBI

UDPIPv4 IPv6

IP FR

The modules inside the Gb interface subsystem work in the UGBI and its suboards, UEPC andUFEU. The Gb interface subsystem has the following modules:

l SNDCP

The SNDCP module realizes the following functions of the SNDCP protocol:

– Providing the upper-layer protocols, IP or PPP with multiple routes to transmit data forPDP contexts identified by NSAPI

– Realizing protocol compression and data compression

– Realizing fragmentation and reorganization for data packets

l LLC

The LLC module realizes the following functions of the LLC protocol:

– Providing the upper-layer protocols, SMS, SNDCP, and GMM with logical linkconnection in acknowledged and unacknowledged modes

– Transmitting signaling and data between the SGSN and MS

– Encrypting with the UEPC

l BSSGP

The BSSGP module realizes the functions of the BSSGP protocol. The BSSGP moduleconsists of the PTP module and the SIG module. The PTP module has the followingfunctions:

– Transmitting cell data, providing the upper-layer protocols with the data transmissionchannel in the acknowledged mode, and controlling downlink traffic


System Principle


Issue 03 (2009-05-27)

– Reporting the GMM the MS radio status message received from the BSS. The GMMinforms the PTP module if the radio access capability changes

The SIG module performs BVC management and paging function.l NS

The NS module realizes the functions of the NS control sublayers including NSVCmanagement and transmission of uplink and downlink data.

l Encryption/DecryptionThe encryption/decryption module is in the UEPC, subboard of the UGBI. The moduleencrypts and decrypts the data in the LLC layer.

NOTE

The UEPC is an optional board.

l FRThe FR module processes the FR protocol. It is in the UFEU, subboard of the UGBI.The UFEU processes the FR data frames and transmits the data to the PCU through thePVC.

4.3.2 The procedure for processing Gb packets in the Gb interfacesubsystem

Handling Gb-interface messages is a process in which the SGSN receives Gb-interface messagesand then distributes them to the related modules for processing.

Figure 4-5 shows the procedure for processing Gb packets in the Gb interface subsystem.



4-9

Figure 4-5 Procedure for processing Gb packets in the Gb interface subsystem.

UEPI

NS

FR

BSSGP

LLC

SNDCP

UFEU

UGFU

BSS

USPU

Encryption/Decryption

UDPIP

UPIU

UGFU

UGBI

IP packets FR frame

FR frameIP packets

NS datapackets

BSSGP datapackets

LLC datapackets

SNDCP datapackets

User planedata packets

L3signaling

LLC datapackets

UEPC

The steps for processing Gb packets in the Gb interface subsystem are as follows:

NOTE

The above figure describes only the processing procedure when the SGSN receives Gb packets. Theprocessing procedure when the SGSN sends Gb packets is opposite to the procedure when the SGSNreceives Gb packets.


System Principle


Issue 03 (2009-05-27)

1. The data from the BSS to the SGSN can enter the UGBI board in the following two ways:l Gb interface carried by FR

After the data enters the UFEU through the UEPI, the FR module encapsulates the dataframe and forwards it to the NS module in the UGBI.

l Gb interface carried by IPAfter the data enters the UGFU through the UPIU, the UGFU processes the IP layerand UDP layer for the IP packets. Based on the destination port number and destinationIP address, the UGFU forwards the data to the NS module in the UGBI through theinternal communication system.

2. The NS module decapsulates the received data packets and processes the signaling pertinentto the module, such as NSVC link management signaling. For the upper-layer data, the NSmodule sends it to the BSSGP module for processing.

3. The BSSGP module decapsulates the received data packets and processes the signalingpertinent to the module, such as cell management signaling. For the upper-layer data, theBSSGP module sends it to the LLC module for processing.

4. The LLC module decapsulates the received data packets and processes them based on theirdata types:l The LLC module processes its relevant signaling, such as LLC link management

signaling.l For the data to be sent to the SNDCP module, the UFEC board decapsulates the data

before the LLC module sends it to the SNDCP module.l For L3 signaling, the LLC module directly sends it to the USPU board for processing.

5. The SNDCP module decapsulates the received data packets. If the TCP/IP header iscompressed, the module decompresses the header. If the user data is compressed, the datais sent to the UEPC for decompression before it is forwarded to the UGFU for processing.

4.4 Iu Interface Control Plane SubsystemThe Iu interface control plane subsystem realizes the functions of the SAAL, MTP3B, SCCP,and RANAP layers for the Iu interface control plane.

The Iu interface control plane subsystem works in the UICP board. When the Iu interface usesIP bearer, the functions of the SCCP layer below are realized in the USIG and UGFU.

NOTE

The Iu interface user plane transfers data according to the GTP protocol. The Gn/Gp interface subsystemrealizes the basic functions for the Iu interface user plane.

4.4.1 The structure of Iu Interface Control Plane SubsystemThe Iu interface control plane subsystem works in the UICP board. When the Iu interface usesIP bearer, the functions of the SCCP layer below are realized in the USIG and UGFU.

4.4.2 The procedure for signaling processing in the Iu interface signaling subsystemHandling Iu-interface signaling is a process in which the SGSN receives and sends the Iu-interface signaling packets.

4.4.1 The structure of Iu Interface Control Plane SubsystemThe Iu interface control plane subsystem works in the UICP board. When the Iu interface usesIP bearer, the functions of the SCCP layer below are realized in the USIG and UGFU.



4-11

Figure 4-6 shows the modules inside the Iu interface control plane subsystem.

Figure 4-6 Modules inside the Iu interface control plane interface subsystem

RANAP

SCCP

MTP3B

SSCF

UICP

SCTPIPv4 IPv6

IP

SSCOP

USIG

M3UA

UGFU

ATM

UGFU

USPU

The Iu interface control plane subsystem consists of the following modules:

l RANAPThe RANAP establishes, releases, and modifies the radio access bearer. The RANAPmodule realizes the following functions of RANAP:– Transferring the serving RNC and changing the SRNC function and relevant resources

– RAB management, including the establishment, modification, and release of RAB

– Releasing Iu resources

– Transferring SRNS contexts

– Iu interface overload control

– Iu interface reset

– Sending the UE Common ID message to the RNC

– Paging users

– Transferring NAS information

– Controlling the UTRAN security mode


System Principle


Issue 03 (2009-05-27)

– Controlling the report on location information

– Reporting common faults

l SCCPThrough the SS7 network, the SCCP module establishes the connectionless and connection-oriented network services between the signaling points and transmits the circuit-based andnoncircuit-based signaling in addition to information of other types. The SCCP module canestablish logical connection in the SS7 network, and thus provide end-to-end signalingtransfer between the signaling points.The SCCP module realizes the following functions of SCCP:– Establishing temporary and permanent logical connection, including routing and IP

address switch.– Providing four-class services: class 0–connectionless, class 1–connectionless with order

guaranteed, class 2–connection-oriented, and class 3–connection-oriented based ontraffic control. The RANAP supports only class2 and class 0 services.

– Segmentation and reassembly functions.

– Connection release.

– SCCP management, such as managing the SCCP module state, informing other nodesof the module state change, and modifying the changed data.

l MTP3BThe MTP3B module enhances B-ISDN support function based on MTP-3 of the SS7network.The MTP3B module realizes the following functions of MTP3B:– Processing signaling messages, which contains message identification, allocation, and

routing.A message is reported to the MTP3B from the SSCF layer through the primitiveinterface. Message identification function judges whether the destination point code(DPC) of the message is consistent with the signaling point code of the SGSN. If thetwo are same, the SGSN carries out allocation function to send the message to the userby judging the service indicator (SI) in the service information octet (SIO). If the twoare not same, the SGSN carries out signaling routing function.

– If the signaling message is sent from the SCCP layer to the MTP-3B, the signalingrouting function is directly carried out.

– Signaling network management function is used to control the constitution of thesignaling network, reassemble the network when it is faulty, and thus ensuring thatsignaling messages can be correctly sent.Signaling network management consists of signaling service management, signalinglink management, and signaling route management.The signaling service management is used to transfer the signaling service from onesignaling link or route to another signaling link(s) or route(s) or reduce the signalingservice in the case of the signaling network congested.The signaling route management is used to transmit the information about the signalingnetwork state to block and unblock the signaling routes.The signaling link management is used to control the locally connected signaling links,recover the faulty signaling links, idle connection, and links that are not located, as wellas disconnect the located links.

l SSCF



4-13

The SSCF (Q.2140) is used to switch the primitive, namely mapping between the signalingentities, MTP-3B of the SS7 and SSCOP at the network node interface (NNI). This ensuresthat the SSCOP of SAAL-UNI is the same as that of SAAL-NNI. The interface for theMTP-3B is mapped into the SSCOP primitive interface through the SSCF.The SSCF (Q.2140) realizes the following functions:– Mapping of the primitive. The SSCF maps the SAAL user primitive into the SSCOP

primitive.– Retrieving local data, which supports switch of MTP-3B links.

– Traffic control. When the low-level links are congested, the SSCF informs theinformation to the high-level links.

– Changing the link states and reporting the information to the upper-layer managemententities.

l SSCOPThe SSCOP (Q.2110), main protocol of the SAAL, carries out adaptation to the ATMsignaling protocol. It provides the upper layers with reliable and orderly data transfer andtraffic control by establishing and maintaining the ATM signaling channel.The SSCOP module realizes the following functions of SSCOP:– Guaranteeing continuity of the order when transferring SSCOP-SDUs.

– Rectifying retransmission.

– Controlling traffic through the sliding window mechanism. The receiving station cancontrol the data transfer rate of the sending station.

– Reporting the errors to the upper-layer management entities.

– Keeping the links.

– Retrieving local data. The local SSCOP users can retrieve the SDUs that are not releasedby the SSCOP entities in order.

– Connection control. Establishing, releasing, and re-synchronizing the SSCOPconnection.

– Transmitting acknowledged and unacknowledged user data.

– Rectifying and recovering the protocol errors.

– Allowing the peer entities to change state information.

4.4.2 The procedure for signaling processing in the Iu interfacesignaling subsystem

Handling Iu-interface signaling is a process in which the SGSN receives and sends the Iu-interface signaling packets.

Figure 4-7 shows the procedure for signaling processing in the Iu interface signaling subsystem.


System Principle


Issue 03 (2009-05-27)

Figure 4-7 Procedure for signaling processing in the Iu interface signaling subsystem

UPIU

ATM switch

UGFU

MTP3B

SCCP

RANAP

SSCF

M3UA

SCTP

IP

UPIU

UGFU

Routing

USIG

UICP

USPU

ATM cells IP packets

ATM cellsIP packets

IP packets

SAAL datapackets

MTP3Bsignaling

SCCPsignaling

RANAPsignaling

L3 signaling

SCCPsignaling

SCTPpackets

M3UAsignaling

RNC RNC

SSCOP

The steps for processing signaling in the Iu interface subsystem are as follows:

NOTE

The above figure describes only the processing procedure when the SGSN receives Iu packets. Theprocessing procedure when the SGSN sends Iu packets is opposite to the procedure when the SGSN receivesIu packets.

1. Step 1 The signaling from the RNC to the SGSN can enter the UICP board in the followingtwo ways:l Iu interface carried by ATM



4-15

The signaling enters the UICP board after it is forwarded by the UGFU board throughthe ATM.

l Iu interface carried by IP

The signaling enters the USIG board after it is forwarded by the UGFU board throughthe IP. The USIG board sends the SCCP message to the SCCP layer of the UICP boardfor processing after handling the IP, SCTP, and M3UA layers.

2. After receiving the Iu interface signaling message from the UGFU, the UICP send it to theSSCOP and SSCF for combination and adaptation, and then to the MTP3B module.

3. After receiving the signaling message, the MTP3B module processes the message basedon the message type. For the message pertinent to the module, such as the MTP3B linkmanagement message, the MTP3B module processes the message itself. For the SCCPmessage, the MTP3B module sends it to the SCCP module for processing.

4. After receiving the signaling message from the USIG or MTP3B module, the SCCP moduleprocesses the message based on the SSN. For the message pertinent to the module, such asthe SCCP state management message, the SCCP module processes the message itself. Forthe RANAP message, the SCCP module sends it to the RANAP module for processing.

5. After processing the RANAP signaling, the RANAP module processes the message basedon the message type. For the message pertinent to the module, such as the RAB assignmentmessage, the RANAP module processes the message itself. For the SM, MM, and SMSmessages, the RANAP module sends them to the USPU board for processing.

4.5 Gn/Gp Interface SubsystemThe Gn/Gp interface subsystem realizes the following functions:GTP-C signalingforwarding,NTP client,DNS client,GTP data packets forwarding between the Gn/Gp interfaceand Iu interface or between the Gn/Gp interface and Gb interface

4.5.1 The structure of Gn/Gp Interface SubsystemThe Gn/Gp interface subsystem works in the UGTP and UGFU boards.

4.5.2 The procedure for User Data forwardingForwarding user data is a process in which the SGSN receives the user-plane data and thenforwards the data to the related interfaces.

4.5.3 Procedure for Processing Gn/Gp Signaling DataHandling Gn/Gp signaling is a process in which the SGSN receives the Gn/Gp signaling andthen distributes the signaling to the related modules for processing.

4.5.4 Procedure for DNS ResolutionDNS resolution refers to the processing procedure performed in the internal modules after theSGSN initiates the domain name resolution.

4.5.5 Procedure for NTP SynchronizationNTP synchronization refers to the processing procedure performed in the internal modules afterthe SGSN initiates the NTP synchronization.

4.5.1 The structure of Gn/Gp Interface SubsystemThe Gn/Gp interface subsystem works in the UGTP and UGFU boards.

Figure 4-8 shows the modules inside the Gn/Gp interface subsystem.


System Principle


Issue 03 (2009-05-27)

Figure 4-8 Modules inside the Gn/Gp interface subsystem

DNS

NTP

GTPC

UDP

UGTP

IP

IPv4

ATM

USPU

IPv6

Data forwarding

IP routing ATMforwarding

UGFU

GTPUcontexts

management

NOTE

The UGTP board can realize the functions of three types, namely GTP-C, GTP-U, and both of them. Theconfiguration data for the UGTP board determines which type of function can be realized.

The Gn/Gp interface subsystem consists of the following modules:

l GTP-CWhen the UGTP receives the GTP-C messages, the GTP-C module distributes the GTP-Cmessages according to the following rules:– If the flow identity for the GTP header in the GTP-C V0 version or TEID in the GTP-

C V1 version is invalid, the UGTP directly sends the message to the USPU assigned bythe SGSN.

– If the flow identity or TEID is valid, the UGTP sends the message to the USPU thatcorresponding to the flow identity or TEID.

l DNSThe DNS module realizes the DNS agent function.The UGTP receives the domain name resolution request from the USPU, and interworkswith the DNS server to return the resolution result to the USPU.Domain name resolution is used to resolve the GGSN IP address based on the APN whenthe PDP context is activated, resolve the peer SGSN IP address based on the RAI duringinter-RAU, and resolve the peer SGSN IP address based on the RNC ID during relocation.Domain name resolution can appeal to the following three means:– Using the DNS server– Using the DNS cache– Using the hostfileThe DNS is a server specially used for domain name resolution in the network. Saved inthe local SGSN, the hostfile contains fewer records than the DNS. The DNS cache, located



4-17

in the UGTP, is the cache for the domain names and IP addresses resolved by the DNS.The cache is used to quickly resolve the domain names, and thus reducing the time forvisiting the DNS. The records saved in the cache has a lifecycle, so when the lifecycleexpires, the records become invalid.The SGSN carries out domain name resolution in the following steps:

1. Look up the host information in the hostfile of the UGTP2. Look up the host information in the DNS cache of the UGTP if no record is found in

step 13. Send the domain name resolution requirement to the DNS server if no record is found

in step 1 and step 2l NTP

The NTP module realizes the NTP client function.The UGTP has the NTP client function and it can interwork with the NTP server tosynchronize the local time for the SGSN. The SGSN9810 supports the third version of theNTP protocol.The SGSN can connect with the NTP server in the following two ways:– Through the service network, namely the port on the UGFU.

– Through the maintenance network, namely the port on the UOMU.

l GTPU context managementThe GTPU context management module realizes the GTPU context management function.Every time an MS activates the PDP contexts, the GTPU contexts are generated. Thesecontexts contain the information about data transfer and forwarding, which are used by theUGTP for processing the data.

l Data transferThe data transfer module realizes forwarding data packets between the Gn/Gp interfaceand Iu interface or between the Gn/Gp interface and Gb interface. This function is the mostimportant in the Gn/Gp subsystem.

4.5.2 The procedure for User Data forwardingForwarding user data is a process in which the SGSN receives the user-plane data and thenforwards the data to the related interfaces.

Figure 4-9 shows the procedure for forwarding user data.


System Principle


Issue 03 (2009-05-27)

Figure 4-9 Procedure for forwarding user data

IP ATM

Data forwarding

IP routing ATMforwarding

UGFU

UGBI

UPIU

MAC

UPIU

ATMSAR

GGSN RNC

2.5G data

3Gdata

The steps for forwarding user data are as follows:

NOTE

The above figure describes only the processing procedure when the SGSN receives GGSN packets. Theprocessing procedure when the SGSN sends RNC or BSS packets is opposite to the procedure when theSGSN receives GGSN packets.

1. After receiving the data packets from the GGSN, the SGSN sends them to the IP routingmodule in the UGFU board to process the IP layer and UDP layer of the packets

2. The IP routing module sends the processed GTP packets to the data transfer module.

For the 2.5G data packets, the data transfer module re-encapsulates them into the internalpackets before sending the packets to the UGBI for processing.

For the 3G data packets, the data transfer module re-encapsulates the payload in the GTPpackets and then sends the new GTP packets to the RNC through the ATM forwardingmodule or IP routing module.



4-19

4.5.3 Procedure for Processing Gn/Gp Signaling DataHandling Gn/Gp signaling is a process in which the SGSN receives the Gn/Gp signaling andthen distributes the signaling to the related modules for processing.

Figure 4-10 shows the procedure for processing the Gn/Gp signaling data.

Figure 4-10 Procedure for processing the Gn/Gp signaling data

IP

IP route

UGFU

UPIU

MAC

GGSN

GTPC

USPU

UGTP

IP packets

IP packets

IP packets

GTPCsignaling

The steps for processing the Gn/Gp signaling data are as follows:

NOTE

The above figure describes only the processing procedure when the SGSN receives GGSN packets. Theprocessing procedure when the SGSN sends GGSN packets is opposite to the procedure when the SGSNreceives GGSN packets.

1. After receiving the signaling data from the GGSN, the SGSN sends it to the IP routingmodule in the UGFU board. Based on the destination IP address, namely the IP address ofthe UGTP, the IP routing module forwards the data to the UGTP.

2. After processing the IP layer and UDP layer of the signaling, the UGTP sends the GTPCmessage to the GTPC module.


System Principle


Issue 03 (2009-05-27)

3. The GTPC module decapsulates the GTPC message and sends it to the USPU in the internalmessage form.

4.5.4 Procedure for DNS ResolutionDNS resolution refers to the processing procedure performed in the internal modules after theSGSN initiates the domain name resolution.

Figure 4-11 shows the procedure for DNS resolution.

Figure 4-11 Procedure for DNS resolution

IP

IP routing

UGFU

UPIU

MAC

DNS Server

DNS

USPU

UGTP

DNSrequest

IP packets

IP packets

IP packets

DNSresponse

The steps for DNS resolution are as follows:

1. After receiving the DNS resolution request from the USPU, the DNS module in the UGTPlooks up the resolution record in the local hostfile and DNS cache in the UGTP. If the recordis found, the DNS module returns the resolution result to the USPU. If the record is notfound, the DNS module sends the DNS resolution request to the DNS server.

2. The IP routing module in the UGFU sends the DNS resolution request to the DNS serverthrough a proper port on the UPIU.



4-21

3. The DNS server sends the resolution result to the SGSN. After the UPIU and UGFU boardsprocess the resolution result, it is sent to the UGTP that initiates the resolution request, andthen to the USPU board.

4.5.5 Procedure for NTP SynchronizationNTP synchronization refers to the processing procedure performed in the internal modules afterthe SGSN initiates the NTP synchronization.

Figure 4-12 shows the procedure for NTP synchronization.

Figure 4-12 Procedure for NTP synchronization

IP

IP routing

UGFU

UPIU

MAC

NTP Server

NTP

Active URCU in the switchingsubrack

UGTP

IP routing

MAC

UOMU

UFSU

IP

NTP Server

Internal timesynchronization message

IP packets

IP packets

IP packets

IP packets

IP packets

IP packets

Otherboards

OtherboardsInternal time

synchronizationmessage

The steps for NTP synchronization are as follows:

1. The NTP module in the UGTP board sends the synchronization request to the NTP server.


System Principle


Issue 03 (2009-05-27)

2. The synchronization request can be sent to the NTP server through the UGFU and its backboard, the UPIU, or the UOMU and its back board, the UFSU.

3. The NTP server returns the synchronization result to the NTP module through the UPIUand its front board, the UGFU, or the UFSU and its front board, the UOMU.

4. The NTP module processes the synchronization result and then sends the result to the activeURCU in the switching subrack through the internal message. The active URCU completestime synchronization for the whole SGSN system.

NOTE

The NTP module regularly sends the synchronization request to the NTP server.

4.6 Signaling SubsystemThe signaling subsystem realizes the functions of MTP L1/L2/L3, or SCTP and M3UA ofSIGTRAN for SS7 in addition to SCCP, MAP, TCAP, CAP, MM, SM, SMS, CAMEL, andBSSAP+ protocol layers.

4.6.1 The structure of Signaling SubsystemThe signaling subsystem works in the USPU and USIG boards. The USIG board realizes thefunctions of SCTP and M3UA layers, while other functions are realized by the USPU board.

4.6.2 Procedure for L3 SignalingHandling L3 signaling is a process in which the internal modules handle the L3 signaling afterthe SGSN receives the signaling from an MS.

4.6.1 The structure of Signaling SubsystemThe signaling subsystem works in the USPU and USIG boards. The USIG board realizes thefunctions of SCTP and M3UA layers, while other functions are realized by the USPU board.

Figure 4-13 shows the modules inside the signaling subsystem.



4-23

Figure 4-13 Modules inside the signaling subsystem

UEPI

MTP2

USS7

MTP3

SCCP M3UA

SCTP

IP

UPIU

UGFU

Routing

USIG

TCAPCAP BSSAP+

MM/SM/SMS/LCS

UGBI/UGTP/UICP

No.7 signallingpoint, such as

HLR

USPU

MAP

The signaling subsystem consists of the following modules:

l MM

The MM module realizes 2.5G and 3G mobility management, establishes contexts forsubscribers, and carries out attach, detach, location update, and intersystem change.

l SM


System Principle


Issue 03 (2009-05-27)

The SM module carries out session management for subscribers by establishing, releasing,and modifying PDP contexts. During this process, the module establishes and releasesconnection between the MS and SGSN.

l SMSThe SMS module realizes short message mobile originated (SM-MO), short messagemobile terminated (SM-MT), and short message alert (SMAlert) functions. It generates afault report in the case of abnormity in short messages.

l LCSLocation services (LCS) provide user location information in a standard format foroperators, common service suppliers, and value added service suppliers. The SGSN carriesout user authentication and location request management.

l MAPThe SGSN communicates with the entities in the GSM network through the MAP signalingprotocol.– Gr interface

The Gr interface is an interface used to exchange information about MS location anduser management between the SGSN and HLR.The SGSN provides the HLR with MS location. The HLR sends the mobile subscribers'information required for services to the SGSN.

– Gd interfaceThe Gd interface is an interface used to exchange SM information between the SGSNand SMS-GMSC or between the SGSN and SMS-IWMSC.

– Gf interfaceThe Gf interface is an interface used to check international mobile station equipmentidentity (IMEI) for subscribers between the SGSN and EIR.

– Lg interfaceThe Lg interface is an interface between the SGSN and GMLC. The GMLC sends theUE location query request and receives the UE location response through this interface.

– Through cooperation with GTP, the SGSN also supports GTP-MAP. The GTP-MAP isused in the case when the GGSN need originating PDP contexts but the GGSN itselfdoes not has the No.7 MAP interface. In such a case, the GGSN sends a request to theSGSN that can support GTP-MAP switch. The SGSN then sends the information fromthe HLR to the GGSN through the GTP message.

l TCAPTransaction capabilities refer to a series of communication capabilities that provide aninterface between applications and a network layer service.The TCAP defines a public function and is independent of specific applications.

l BSSAP+ signalingThe BSSAP+ signaling cooperates with the GMM/PMM to exchange the Gs interfaceinformation between the SGSN and MSC/VLR.

l CAPThe CAP signaling realizes interworking between the SGSN and CAMEL gsmSCF throughthe Ge interface. The SGSN informs the gprsSSF of the monitored user events, such asattach, PDP context activation, and SMS so that the gprsSSF can control the user's actions.

l MTP3 and MTP2



4-25

The MTP3 and MTP2 realize functions of the MTP layer for SS7. The USS7, subboard ofthe USPU realizes the MTP2. The USPU board realizes the MTP3.

l M3UA and SCTPThe M3UA and SCTP realize the IP bearer for SS7 on the USIG board.

4.6.2 Procedure for L3 SignalingHandling L3 signaling is a process in which the internal modules handle the L3 signaling afterthe SGSN receives the signaling from an MS.

Figure 4-14 shows the procedure for signaling processing.


System Principle


Issue 03 (2009-05-27)

Figure 4-14 Procedure for signaling processing

UEPI

MTP2

USS7

MTP3

SCCP

M3UA

SCTP

IP

UPIU

UGFU

Routing

USIG

TCAPCAP BSSAP+

MM/SM/SMS/LCS

UGBI

HLR and otherdevices

No.7 signaling IP packets

IP packets

IP packets

SCTPsignaling

M3UAsignaling

No.7 signaling

MTP3 signaling

SCCPsignaling

CAPsignaling

BSSAP+signaling

TCAPsignalling

L3 signaling

Iu interfacesignaling

UGTP UICP

Gn/Gp interfacesignaling

Gb interfacesignaling

USPU

MAP

Map signalling

The steps for processing signaling are as follows:

NOTE

The above figure shows the Gb or Iu interface signaling exchanged with the HLR.



4-27

1. The signaling from the Gb or Iu interface is sent to the SM, MM, LCS, or SMS module inthe USPU for processing.

2. Through the internal message, the SM, MM, LCS, or SMS module informs the MAPmodule of encapsulating the signaling or sending the signaling to the Gn/Gp interfacesubsystem in the UGTP for processing.

3. After encapsulating the upper-layer signaling, the MAP module sends it to the TCAP layer.4. After encapsulating the MAP signaling, the TCAP module sends it to the SCCP layer.5. After encapsulating the TCAP message to the SCCP message, the SCCP layer sends the

SCCP message to the MTP or M3UA module for processing.6. The MTP module adds the MTP header for the SCCP message and chooses a proper link

to send the message to the HLR or other SS7 nodes. The M3UA module adds the M3UAheader for the SCCP message and chooses a proper SCTP link. After encapsulating thesignaling to the IP packets, the M3UA module sends them to the SS7 nodes supporting theIP through the UGFU.

4.7 Typical Data Processing ProcedureThe procedure for handling the typical data contains signaling and data handling.

4.7.1 2.5G signaling data flowHandling 2.5G signaling data flows is a process in which the internal modules handle the 2.5Gsignaling data after the SGSN receives the data from the Gb interface.

4.7.2 3G signaling data flowHandling 3G signaling data flows is a process in which the internal modules handle the 3Gsignaling data after the SGSN receives the data from the Iu interface.

4.7.3 2.5G service data flowHandling 2.5G service data flows is a process in which the internal modules handle the 2.5Gservice data after the SGSN receives the data from the Gb interface.

4.7.4 3G service data flowHandling 3G service data flows is a process in which the internal modules handle the 3G servicedata after the SGSN receives the data from the Iu interface.

4.7.1 2.5G signaling data flowHandling 2.5G signaling data flows is a process in which the internal modules handle the 2.5Gsignaling data after the SGSN receives the data from the Gb interface.

The 2.5G uplink signaling data flow enters the SGSN from the BSS. The SGSN processes thesignaling and exchanges it with the HLR or GGSN upon requirement.

The 2.5G downlink signaling data flow enters the SGSN from the HLR or GGSN. The SGSNprocesses the signaling and exchanges it with the BSS upon requirement.

The following illustrates the processing procedure for 2.5G uplink signaling data flow, as shownin Figure 4-15.


System Principle


Issue 03 (2009-05-27)

Figure 4-15 Processing procedure for 2.5G uplink signaling data flow

UGFU

USPU

UGBI

UEPI

UPIU

URCU

UBIU

USIG

UFCU

UPIU

UGTP

UGFU

UPIU

UFCU

UPIU

BSS

GGSN、SG

HLRand

otherdevices

URCU

UBIU

UEPI

BSS

The steps for processing the 2.5G uplink signaling data flow are as follows:

1. The signaling from the BSS to the SGSN can enter the UGBI board in the following twoways:

l Gb interface carried by FR

The signaling directly enters the UGBI through the UEPI.

l Gb interface carried by IP

The signaling enters the UGFU through the UPIU. Then the UGFU forwards thesignaling to the UGBI through the internal communication system.

2. After receiving the signaling from the BSS, the UGBI sends it to the protocol layers forprocessing. For the signaling between the MS and SGSN, the UGBI forwards it to the USPUfor processing.

3. The USPU processes the signaling based on their types:

l Signaling related to the MM or SMS modules

This type of signaling should be exchanged with the SS7 nodes, such as the HLR orSMC. In this case, the USPU processes the signaling based on the bearer types of SS7.

– TDM bearer

The USPU exchanges the signaling with the SS7 nodes through the UEPI.

– IP bearer

The USPU exchanges the signaling with the SS7 nodes through the USIG andUGFU.

l Signaling related to the PDP contexts

This type of signaling should be exchanged with the GGSN. In this case, the USPU firstsends the signaling to the UGTP, and then the UGTP exchanges the signaling with theGGSN through the IP interface provided by the UGFU.



4-29

4.7.2 3G signaling data flowHandling 3G signaling data flows is a process in which the internal modules handle the 3Gsignaling data after the SGSN receives the data from the Iu interface.

The 3G uplink signaling data flow enters the SGSN from the RNC. The SGSN processes thesignaling and exchanges it with the HLR or GGSN upon requirement.

The 3G downlink signaling data flow enters the SGSN from the HLR or GGSN. The SGSNprocesses the signaling and exchanges it with the RNC upon requirement.

The following illustrates the processing procedure for 3G uplink signaling data flow, as shownin Figure 4-16.

Figure 4-16 Processing procedure for 3G uplink signaling data flow

UGFU

USPU

UICP

UEPI

UPIU

URCU

UBIU

USIG

UFCU

UPIU

UGTP

UGFU

UPIU

UFCU

UPIU

RNC

GGSN,SG,and otherdevices

HLRand

otherdevices

URCU

UBIU

USIG

The steps for processing the 3G uplink signaling data flow are as follows:

1. The signaling from the RNC to the SGSN can enter the UICP board in the following twoways:l Iu interface carried by ATM

The signaling directly enters the UICP after it is forwarded by the ATM module in theUGFU.

l Iu interface carried by IPThe signaling enters the USIG after it is forwarded by the IP module in the UGFU.Then the USIG sends the SCCP message to the UICP for processing.

2. After receiving the signaling from the RNC, the UICP sends it to the protocol layers forprocessing. For the signaling between the MS and SGSN, the UICP forwards it to the USPUfor processing.

3. The USPU processes the signaling based on their types:l Signaling related to the MM or SMS modules


System Principle


Issue 03 (2009-05-27)

This type of signaling should be exchanged with the SS7 nodes, such as the HLR orSMC. In this case, the USPU processes the signaling based on the bearer types of SS7.– TDM bearer

The USPU exchanges the signaling with the SS7 nodes through the UEPI.– IP bearer

The USPU exchanges the signaling with the SS7 nodes through the USIG andUGFU.

l Signaling related to the PDP contextsThis type of signaling should be exchanged with the GGSN. In this case, the USPU firstsends the signaling to the UGTP, and then the UGTP exchanges the signaling with theGGSN through the IP interface provided by the UGFU.

4.7.3 2.5G service data flowHandling 2.5G service data flows is a process in which the internal modules handle the 2.5Gservice data after the SGSN receives the data from the Gb interface.

The 2.5G uplink service data flow enters the SGSN from the Gb interface. After processed bythe SGSN, the data flow is forwarded from the Gn/Gp interface.

The 2.5G downlink service data flow enters the SGSN from the Gn/Gp interface. After processedby the SGSN, the data flow is forwarded from the Gb interface.

The following illustrates the processing procedure for 2.5G uplink service data flow, as shownin Figure 4-17.

Figure 4-17 Processing procedure for 2.5G uplink service data flow

UGFU

UGBI

UPIU

URCU

UBIU

UFCU

UPIU

BSS UEPI

BSS

GGSN

The steps for processing the 2.5G uplink signaling data flow are as follows:

1. The signaling from the BSS to the SGSN can enter the UGBI board in the following twoways:l Gb interface carried by FR

The signaling directly enters the UGBI through the UEPI.l Gb interface carried by IP

The signaling enters the UGFU through the UPIU. Then the UGFU forwards thesignaling to the UGBI through the internal communication system.

2. After receiving the signaling from the BSS, the UGBI sends it to the protocol layers forprocessing. Then the processed data is forwarded to the UGFU.



4-31

3. Based on the destination IP address of the service data, the UGFU chooses a proper portfor the data that is then sent to the GGSN.

4.7.4 3G service data flowHandling 3G service data flows is a process in which the internal modules handle the 3G servicedata after the SGSN receives the data from the Iu interface.

The 3G uplink service data flow enters the SGSN from the Iu interface. After processed by theSGSN, the data flow is forwarded from the Gn/Gp interface.

The 3G downlink service data flow enters the SGSN from the Gn/Gp interface. After processedby the SGSN, the data flow is forwarded from the Iu interface.

The following illustrates the processing procedure for 3G uplink service data flow, as shown inFigure 4-18.

Figure 4-18 Processing procedure for 3G uplink service data flow

UGFU

UPIU

RNC

GGSN

The steps for processing the 3G uplink signaling data flow are as follows:

1. The data packets from the RNC are sent to the UGFU after processed by the ATM layerand SAR of the UPIU.

2. The UGFU extracts the IP packets from the ATM cells and determines the destinationUGFU for the data based on the destination IP address.

3. The UGFU replaces the GTP header and modifies the tunnel identifier.4. The UGFU finds the route for the data packets based on the destination IP address. Then

the UGFU sends the encapsulated data packets to the GGSN through the UPIU.


System Principle


Issue 03 (2009-05-27)

5 Principle of the Charging System

About This Chapter

The charging system operates in the USPU, UGTP, and UCDR boards. The charging systemcollects, codes, buffers, and sends CDRs as well as provides charging information for the billingcenter.

5.1 The location of the charging system in the SGSNThe charging system operates in the USPU, UGTP, and UCDR boards.

5.2 The structure of the modules in the charging systemThe charging system contains of charging information collection subsystem, CDR codingmodule, Hard disk module

5.3 The procedure for generating a CDRThe procedure for generating a CDR contains the following three steps: Creating a CDR;Generating a partial CDR; Closing a final CDR.

5.4 Processing and Sending a CDRCDRs generated by the USPU and UGTP are sent to the UCDR. The enarging subsystem in theUCDR encodes the CDRs with abstract syntax notation one (ASN.1), encapsulates the CDRs toa GTP' packet and then sent the packet to the CG through the UGFU.

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 5 Principle of the Charging System


5-1

5.1 The location of the charging system in the SGSNThe charging system operates in the USPU, UGTP, and UCDR boards.

The charging system collects, codes, buffers, and sends CDRs as well as provides charginginformation for the billing center.

Figure 5-1 shows where the charging system is located in the SGSN.

Figure 5-1 Location of the charging system in the SGSN

BSS

UICP

Platformmanagement

OM

Gbinterface

subsystem

Platformmanagement

OM

UGBI

Signalingsubsystem

Platformmanagement

OM

USIG

Signalingsubsystem

Platform management

OM

Chargingsystem

USPUUGTP

Platform management

OM

Chargingsystem

URCU

Platform management

OM


subsystem

UFCU


subsystem

Platformmanagement

OM

UGFU

IP routingsubsystem

Platformmanagement

OM

Gn/Gpinterface

subsystem

UOMU

Platformmanagement

OM

UCDR

Chargingsystem

Platformmanagement

OM

BSS

No.7signalling

node, suchas HLR


LMT

BUS

BUS

Service subrack

Switching subrack


subsystem

Gn/Gpinterface

subsystem

E1 E1


Fiber cable

Fiber cable


5 Principle of the Charging SystemHUAWEI SGSN9810 Serving GPRS Support Node

System Principle


Issue 03 (2009-05-27)

5.2 The structure of the modules in the charging systemThe charging system contains of charging information collection subsystem, CDR codingmodule, Hard disk module

Figure 5-2 shows the structure of the charging subsystems.

Figure 5-2 Structure of the charging subsystems

M-CDR

S-CDR

UGTP

Charginginformationcollection

USPU

CDR coding

UCDR

CDR sending

Harddisk

UBSU

UGFU

CG

UPIU

IP

Charginginformationcollection

The charging system contains the following subsystems:

l Charging information collection subsystemThe charging information collection subsystem in the USPU collects M-CDR, S-SMO-CDR, S-SMT-CDR, LCS-MT-CDR, LCS-MO-CDR, and LCS-NI-CDR. Then thesubsystem generates a half-finished CDR and sends the CDR to the UCDR board.The charging information collection subsystem in the UGTP receives traffic informationfrom the UGFU and collects S-CDR. Then the subsystem generates a half-finished CDRand sends the CDR to the UCDR board.



5-3

l CDR coding moduleThe CDR coding module carries out ASN.1 coding for the half-finished CDR and processesit to a finished CDR that is suitable for transmission and complies with the protocol.

l CDR sending moduleThe CDR sending module encapsulates CDRs according to certain protocols, chooses thesuitable CG for the CDRs, and then transfers them through the UGFU.

l Hard disk moduleWhen the SGSN and CG cannot communicate normally, the hard disk module buffersCDRs.

5.3 The procedure for generating a CDRThe procedure for generating a CDR contains the following three steps: Creating a CDR;Generating a partial CDR; Closing a final CDR.

Generating a CDRA CDR contains many domains, such as user identity, service time, and service duration. Thebilling center charges the users based on the CDR information.

The charging subsystem in the USPU and UGTP collects original charging information. Someof the charging information is obtained from the user database or the configuration database,but some dynamic information, such as the service duration is obtained from the specifiedcounter or timer.

The procedure for generating a CDR contains the following three steps:

l Creating a CDRWhen a subscriber uses the service, the system is triggered to create a CDR at a certaincharging point and then records the subsequent charges in the CDR. For example, aftersending an ATTACH ACCEPT message to a user, the SGSN creates a mobilitymanagement generated-charging data record (M-CDR) for the user.

l Generating a partial CDRWhen a subscriber uses the service, the SGSN generates a partial CDR for the user if time,traffic, tariff, or QoS change time reach the set threshold.

l Closing a final CDRWhen the service terminates, the SGSN closes the CDR and generates a final CDR

One or more CDRs may be generated when a subscriber uses a certain service. These CDRs arecombined in the billing center for final charging on the user.

The following takes M-CDR as an example to explain how a CDR is generated.

Creation of M-CDRThe mobility management service starts when an MS attaches to the SGSN, and terminates whenthe MS detaches from the SGSN. Since the service occurs in a series of processes, the creationof an M-CDR is closely related to the connection status between the MS and the SGSN. To bespecific, the creation of an M-CDR contains three steps, creation, generation, and closure.

Table 5-1 lists the MS status in the M-CDR generation procedure.


System Principle


Issue 03 (2009-05-27)

Table 5-1 MS status in the M-CDR generation procedure

M-CDR Generation Procedure MS Status

Creation of a M-CDR Attached to the SGSN

Generation of a partial M-CDR From attached to the SGSN till detached fromthe SGSN and conditions for generating apartial M-CDR are met

Closure of a M-CDR Detached from the SGSN

Figure 5-3 shows the charging flow points for the mobility management service.

Figure 5-3 Charging flow points for the mobility management service

MS Old SGSNBSS/UTRAN

P1

New SGSN HLR

P2

P4

P5

P3

Attach Request

Attach Accept

Attach Complete

Routing Area UpdateRequest

Routing Area UpdateAccept

Routing Area UpdateRequest

Routing Area UpdateAccept

Detach Request

Detach Accept

RAU Update ACK

RAU Update Request

RAU Update Response

Insert Subscriber Data

Table 5-2 describes the charging flow points in Figure 5-3.



5-5

Table 5-2 Description of the charging flow points

Sequence Number Event Network Element

P1 The SGSN creates an M-CDR for the MS.

Old SGSN

P2 The SGSN generates a partialM-CDR after the number oflocation update for the MSreaches the present threshold.

Old SGSN

P3 Inter-SGSN switch occurs tothe MS. The old SGSN closesthe M-CDR.

Old SGSN

P4 Inter-SGSN switch occurs tothe MS. The new SGSNcreates an M-CDR.

New SGSN

P5 The MS detaches from theSGSN. The SGSN closes thefinal M-CDR.

New SGSN

5.4 Processing and Sending a CDRCDRs generated by the USPU and UGTP are sent to the UCDR. The enarging subsystem in theUCDR encodes the CDRs with abstract syntax notation one (ASN.1), encapsulates the CDRs toa GTP' packet and then sent the packet to the CG through the UGFU.

ASN.1 CodingASN.1 is a universal language used worldwide to describe data structure in thetelecommunication field. According to the 3rd generation partnership project (3GPP) protocol,all CDR structures must adopt ASN.1 for description. ASN.1 has the following features:

l Unfixed-length data structureThe description fields of ASN.1 have two types, optional and mandatory. Each filedcontains a triplet of Tag, Length, and Value.

l Cross-platformData structures described by ASN.1 adopt the uniform network byte sequence fortransmission over networks.

Sending a CDRFigure 5-4 shows the procedure for sending a CDR.


System Principle


Issue 03 (2009-05-27)

Figure 5-4 Procedure for sending a CDR

USPU

InternalCDR

SubrackNo:Slot No

UCDR

UGFU

ASN.1 CDR

SubrackNo:Slot No

GTP' header

UDP header

IP header

ASN.1 CDR

GTP' headerUDP header

IP header

CG

UGTP

The steps for sending a CDR are as follows:

1. The USPU or UGTP generates a CDR and sends the CDR to the UCDR.2. The UCDR encapsulates the ASN.1-encoded CDR using GTP, TCP/UDP, and IP in turn

and then sends the encapsulated CDR packet to the UGFU.3. The UGFU queries the internal routing table and sends the CDR to the CG.



5-7

6 Principle of the O&M System

About This Chapter


6.1 The location of the O&M system in the SGSNThe functions of the O&M system are mainly implemented on the UOMU board.

6.2 The structure of the modules in the O&M systemBased on its location, the O&M system can be categorized into two modules, back administrationmodule (BAM) and front administration module (FAM).

6.3 Configuration ManagementData configuration includes operations such as addition, deletion, modification, and query ofsystem data. Actually, data configuration is to manage the configuration database.

6.4 Performance MeasurementPerformance measurement means measuring the SGSN and its surrounding network to obtaindata about network operation.

6.5 Alarm ManagementThe alarm system monitors the systemic operation and informs the maintenance personnel ofthe detected faults or disturbance.

6.6 Query and ControlThe query and control function indicates monitoring, controlling, and testing the hardware andlinks in the system.

6.7 Security ManagementSecurity management means controlling on users and user authorities to ensure that theauthorized users can operate the SGSN within the authorization range.

6.8 User or Interface TracingTracing function is used in the routine maintenance for the SGSN. By tracing the information,you can locate where the fault occurs in the service procedure. After the data is configured forthe SGSN, you can establish tracing to verify if the signaling links are normal, and thus judgewhere the fault occurs.

6.9 Log Management

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle 6 Principle of the O&M System


6-1

The log management subsystem records the generated messages when the system runs and savesthe messages to the UOMU hard disk, and thus facilitates problem location and systemmaintenance.

6.10 External Maintenance InterfaceThe O&M subsystem acts as a bridge to connect the SGSN with users, so the subsystem mustprovide various network management systems with the interconnected interfaces. Currently, theSGSN can provide the command input and output interface and SNMP interface.

6 Principle of the O&M SystemHUAWEI SGSN9810 Serving GPRS Support Node

System Principle


Issue 03 (2009-05-27)

6.1 The location of the O&M system in the SGSNThe functions of the O&M system are mainly implemented on the UOMU board.


Figure 6-1 shows the location of the O&M system in the SGSN.

Figure 6-1 Location of the O&M system in the SGSN

BSS

UICP

Platformmanagement

OM

Gbinterface

subsystem

Platformmanagement

OM

UGBI

Signalingsubsystem

Platformmanagement

OM

USIG

Signalingsubsystem

Platform management

OM

Chargingsystem

USPUUGTP

Platform management

OM

Chargingsystem

URCU

Platform management

OM


subsystem

UFCU


subsystem

Platformmanagement

OM

UGFU

IP routingsubsystem

Platformmanagement

OM

Gn/Gpinterface

subsystem

UOMU

Platformmanagement

OM

UCDR

Chargingsystem

Platformmanagement

OM

BSS

No.7signalling

node, suchas HLR


LMT

BUS

BUS

Service subrack

Switching subrack


subsystem

Gn/Gpinterface

subsystem

E1 E1


Fiber cable

Fiber cable




6-3

Externally, the O&M system provides the network management systems with the uniformhuman-machine language (MML) interfaces that realize the network management systems toaccess the SGSN.

Internally, the O&M system cooperates with the other subsystems to maintain and monitor theSGSN system.

6.2 The structure of the modules in the O&M systemBased on its location, the O&M system can be categorized into two modules, back administrationmodule (BAM) and front administration module (FAM).

l The BAM manages the interactive input and output management between the O&M systemand users. The BAM breaks down and delivers O&M tasks, collects and reports the SGSNmonitoring data. The BAM is in the UOMU.

l The FAM directly interacts with other subsystems. The FAM is located in all the IO boardsin the SGSN.

The BAM and the FAM perform operation and maintenance for the whole SGSN system, asshown in Figure 6-2.

Figure 6-2 Hierarchy of the O&M system

BAM FAM

UOMU

IP

LMT

FAM

UICP

FAM

USPUSGSN

The BAM and the FAM modules consist of the configuration, query and control, performance,alarm, security, tracing, and log management submodules, as shown in Figure 6-3.


System Principle


Issue 03 (2009-05-27)

Figure 6-3 Composition of the O&M system

IP

LMT

Commandprocessing

Securitymanagement

ConfigurationQuery and

controlmanagement

Alarmmanagement

Performancemanagement

Logmanagement

Tracingmanagement

FAM

BAM

UOMU

FAM

Service board

6.3 Configuration ManagementData configuration includes operations such as addition, deletion, modification, and query ofsystem data. Actually, data configuration is to manage the configuration database.

Figure 6-4 shows the configuration management flow.



6-5

Figure 6-4 Configuration management flow

Configurationmanagement

ADD/RMV/MOD/LST/SET

CDBMML.TXT

SAVE CFG

Initialization

Service module

MMLcommand

Dynamic Data Configuration

You can dynamically configure the data when the SGSN works normally.

To configure dynamic data, perform the following steps:

1. You send an MML configuration command through the LMT.

2. After you send the command, the configuration management module resolves the commandand checks the validity for the command.

3. If the command is illegal, the module conducts addition, modification, or deletion of datain the database as directed by the command.

4. The CDB then validates the data that is updated dynamically.

NOTE

For some modification that may affect the normal running of the system, a configuration command onlychanges the information in the database. The modified data takes effect only after the system restarts.

Static Data Configuration

MML.TXT can be manually modified off-line. The modified MML.TXT file is loaded to theUOMU. When the system initializes, the UOMU reads the data from the MML.TXT to updatethe data that is configured statically.


System Principle


Issue 03 (2009-05-27)

Saving and Recovering Configuration

When the system loads or updates the configuration, you must save the updated configurationdata to make them effective all the time.

To save the configuration, perform the following steps:

1. You send the configuration saving command SAVE CFG through the LMT.2. After you send the command, the configuration management module browses through all

the tables in the CDB and converts each record to a certain MML command.3. The converted MML commands are saved in sequence to a new file. Then the new initiation

MML.TXT file forms in the configuration database.

When the system restarts and initializes the CDB, it reads the commands from the initiationMML.TXT file and executes the commands in the file one by one. Then the system writes theconfigured data in the CDB, and thus completes recovering the data before the system starts.

6.4 Performance MeasurementPerformance measurement means measuring the SGSN and its surrounding network to obtaindata about network operation.

6.4.1 The basic concepts of performance measurementPerformance measurement consists of the following basic elements: measurement index,measurement unit, measurement set, measurement object, configurable object, non-configurableobject, and performance task.

6.4.2 Procedure for performance measurementThe procedure for performance measurement includes information collecting, reporting, andprocessing.

6.4.1 The basic concepts of performance measurementPerformance measurement consists of the following basic elements: measurement index,measurement unit, measurement set, measurement object, configurable object, non-configurableobject, and performance task.

Performance measurement means measuring the SGSN and its surrounding network to obtaindata about network operation.

The basic concepts of performance measurement are described as follows:

l Measurement itemIt is also called measurement entity, which is a specific attribute item for statistics.

l Measurement unitIt is a set of measurement items that bear the same attribute.

l Measurement setIt is a set of measurement units that bear the same attribute.

l Measurement objectIt is an entity object that is pointed at by the measurement item.

l Configurable object



6-7

It is an object to be configured by a user. Configurable objects may be in large quantity,such as IMSI. The object may also be unpredictable in the system, such as an access pointname (APN). Therefore, the system cannot measure all the configurable objects.

l Unconfigurable objectIt is an object automatically created by the system, such as a board.

l Performance taskIt consists of measurement unit, measurement cycle, and other attributes. This task collectsall the performance data for all the measured objects on a time basis.

6.4.2 Procedure for performance measurementThe procedure for performance measurement includes information collecting, reporting, andprocessing.

Figure 6-5 shows the procedure for performance measurement.

Figure 6-5 Procedure for performance measurement

BAM performancemanagement

module

Performancedata file

MMLcommand

Resultbuffer area

Performancetask file

Objectarea

FAM performancemanagement

module

FAM performancemanagement

module

Resultreport area

Counterarea

UOMU

Service module

Result data

Result data

Result data

Initial data

Serviceboard

Initialization

Result data

LMT

M2000 client

M2000database

server

Result data

The steps for performance measurement are as follows:

1. System measurement initialization


System Principle


Issue 03 (2009-05-27)

After the system is first started, the BAM performance management module generates theinitial performance task file.

The performance task file records information such as measurement object, measurementperiod, measurement set, measurement unit, and measurement index.

The measurement object is generated by the BAM performance management module afterthe module obtains the measurement data from the system configuration file. Themeasurement period has two types, five minutes and thirty minutes. Measurement set,measurement unit, and measurement index are determined by the system configuration file.

2. Measurement information synchronization

The BAM performance management module synchronizes the measurement taskinformation to all the service boards. The FAM performance management module createsthe object area, counter area, and result reporting area.

3. Data collection

(1) The service modules in the service board collect all types of measurement data andsave it in the counter area. The measurement data is accumulated in the counter.

(2) The FAM performance management module in the service board collects data everyfive minutes and calculates the increment of the data, and saves the data in the resultreporting area.

(3) The FAM performance management module in the service board reports the data inthe result reporting area to the FAM performance management module in the UOMU.

(4) The FAM performance management module in the UOMU gathers the measurementdata reported from all the service boards and then sends the data to the BAMperformance management module.

(5) The BAM performance management module formats the performance measurementresults and then saves the results in the result data file.

NOTE

Performance result data has three types, short-period result file (data measured every 5 minutes),medium-period result file (data measured every 30 minute), and SNMP measurement result file.

The following shows how long these files can be stored in the SGSN:

l The short-period result file can be saved for one day.

l The medium-period result file can be saved for three and a half days.

l The SNMP measurement result file can be saved for seven days.

4. Data reporting

The BAM performance management module regularly sends the measurement resultinformation to the M2000 database server. The M2000 database server obtains the datafrom the UOMU performance data file through the file transfer protocol (FTP) and savesthe data in the database.

The LMT can also automatically obtain the measurement result file from the UOMU harddisk.

For the data of the simple network management protocol (SNMP), the network managementsystem actively obtains and queries the data.

5. Data processing

Through the M2000 client, you can query, analyze, and collect the measurement data savedin the M2000 database server.



6-9

Through the LMT, you can browse through the performance measurement data savedlocally.

6.5 Alarm ManagementThe alarm system monitors the systemic operation and informs the maintenance personnel ofthe detected faults or disturbance.

Based on the alarm type, alarms can be divided into two types:

l Fault alarm

l Event alarm

Based on the alarm severity level, alarms can be divided into four types:

l Critical alarm

l Major alarm

l Minor alarm

l Warning

Figure 6-6 shows the alarm management flow.


System Principle


Issue 03 (2009-05-27)

Figure 6-6 Alarm management flow

Alarmmanagement

module

MMLcommand

FAM

UOMU

Resultdata

M2000 client

LMT

Alarm box

Alarm log fileAlarm bufferarea

LAN

FAM

Service module

Service board

FAM

Service module

Service board

Initial alarm

M2000database

Alarm Generation

If a service board detects abnormity when it runs, an alarm is generated. The generation of thealarm is actually a process of cooperation between the FAM and BAM.

The steps for generating an alarm are as follows:

1. The service module generates an alarm.



6-11

2. The FAM alarm processing module sends the alarm to the BAM alarm processing modulein the UOMU board.

3. The BAM alarm processing module explains the alarm. If the alarm satisfies the shieldingcondition, it is directly discarded. If the alarm does not satisfy the shielding condition, it isreported to the LMT, alarm box, or M2000 database.

4. The maintenance console of the LMT and the M2000 display the alarms in a list and informthe alarm list to the alarm box.

NOTE

l The alarms in the alarm box are from the UOMU, LMT, or M2000 maintenance console. Thesource of an alarm depends on where the alarm box is installed.

l The alarms in the M2000 maintenance console are forwarded by the M2000 database.

Alarm ClearingOnly a fault alarm can be cleared. Alarm clearing has the following situations:

l When the fault is cleared, the service module generates a recovery alarm. The BAM thenclears the saved alarm.

l If the BAM receives the first alarm when a board resets, all the alarms about the board arecleared.

l Expired clearing. If the alarm is not cleared for a period of more than 15 days, the systemautomatically clears the alarm.

l When the LMT receives the alarm clearing, it displays the alarm in grey.

Alarming SavingAfter an alarm is generated, it is saved as the active alarm in the memory or the history alarmin the hard disk.

The active alarm indicates that the alarm is not cleared. When a fault alarm is generated, it isdirectly saved to the active alarm buffer area. The recovery alarm then clears the alarm in thebuffer area. When the system initializes, the alarm processing module retrieves the alarm thatis not cleared in the history alarm log file and generates the active alarm list.

When the alarm saving timer expires, the alarms in the active alarm buffer area are saved to thehistory alarm file. The file can save up to 25,000 alarm records, including fault alarms and eventalarms. If the file reaches the maximum capacity, it cyclically covers the alarms.

Alarm Box OperationWhen the system generates an alarm, the system informs a user through the audible and visualprompt that is performed by the alarm box.

The alarm box has three connection modes:

l Connecting to the serial port on the UOMU

l Connecting to the serial port on the LMT

l Connecting to the serial port on the M2000

Event alarms are not reported to the alarm box. Fault alarms can be reported to the alarm box ifthey are set to report. By judging the setting, the BAM alarm processing module determineswhether to simultaneously report the alarm to the alarm box when the alarm is generated.


System Principle


Issue 03 (2009-05-27)

Through the UOMU board, you can reset the alarm box, reset the alarm indicator, and stop thealarm sound.

6.6 Query and ControlThe query and control function indicates monitoring, controlling, and testing the hardware andlinks in the system.

Figure 6-7 shows the query and control flow.

Figure 6-7 Query and control flow

Query and controlmodule

MMLcommand

FAM

UOMU

Board statusreport

LMT

LAN

FAM

Service module

Service board

FAM

Service module

Service board

Board status

Equipment Maintenance and Status Query

To perform query and control on the SGSN, perform the following steps:

1. You send a query and control command through the maintenance console.2. After you send the command, the query and control module resolves the command and

sends the query and control message to the board.



6-13

3. The board executes the command or obtains the board status. Then the board sends theboard status to the BAM in the UOMU board through a message.

In the procedure for common query control, the BAM or the FAM only acts as a bridge to transmitmessages. The specific operation should be performed by the service module.

Status ReportThrough the LMT panel, you can view the hardware structure and status messages of the SGSN.When the board status changes, the status is updated in real-time on the panel, which is realizedby the automatic report of board status.

The steps for reporting the board status are as follows:

1. When the board status changes, the message of the board status is generated. When theBAM on the UOMU receives the message of board status change, the status report isgenerated and then is reported to the LMT.

2. The LMT updates the panel in real-time based on the report.

The procedure for reporting CPU occupation rate is similar to that for reporting board status.

6.7 Security ManagementSecurity management means controlling on users and user authorities to ensure that theauthorized users can operate the SGSN within the authorization range.

6.7.1 Domain ManagementThe SGSN classifies users into two domains: the local domain and M2000 domain. Theadministrator independently manages the user in any one of the domain, but the administratorin one domain cannot manage the users in the other domain.

6.7.2 User AuthoritiesThe authority of an operator is classified to five levels.

6.7.3 User Name and PasswordA user name is composed of up to 32 characters containing only alphabets and digits. It is caseinsensitive and must start with an alphabet.

6.7.4 Command GroupsA command group is a set of commands. Commands form some command groups, and then thecommand groups are assigned to users with different authorities for administration management.A command can be in multiple command groups.

6.7.1 Domain ManagementThe SGSN classifies users into two domains: the local domain and M2000 domain. Theadministrator independently manages the user in any one of the domain, but the administratorin one domain cannot manage the users in the other domain.

The users in the two domains adopt different authentication methods, as shown in Figure 6-8.


System Principle


Issue 03 (2009-05-27)

Figure 6-8 Procedure for user authentication

Securitymanagement

module

UOMU

LMT

Authenticationrequest

Authenticationresponse M2000

Domain userauthenticationrequest

Domain userauthenticationresponse

Local userinformation

Authenticationrequest

Authenticationresponse

For the users that log in to the local domain, the SGSN authenticates them based on the userinformation file saved locally.

For the users that log in to the M2000 domain, the SGSN sends the user authenticationinformation to the M2000, and then the M2000 authenticates the users.

6.7.2 User AuthoritiesThe authority of an operator is classified to five levels.

The user authorities are classified into five groups as shown in Table 6-1.

Table 6-1 User groups and authorities

Authority Data Query SystemMaintenance

DataConfiguration

Administration

Guest √ - - -

User √ √ - -

Operator √ √ √ -

Administrator √ √ √ √

Custom When adding a user, you can assign every privilege to this user.

NOTE

"√" in Table 6-1 indicates the authority for the corresponding user group.

The command groups for the Guest, User, Operator, and Administrator are predefined in the LMT system.

6.7.3 User Name and PasswordA user name is composed of up to 32 characters containing only alphabets and digits. It is caseinsensitive and must start with an alphabet.

A user account consists of a user name and a password.



6-15

The length and character combination of a password are set by a user.

The LMT has two users:

l admin: The initial password is sgsnadmin. The admin has the highest authority and canexecute all the commands. Initially, the admin adds the other users and cannot be deleted.The password of admin can only be modified by the admin.

l guest: The initial password is guestguest. The guest only has the log in, log out, and queryauthorities.

NOTE

A user can change only his password.

6.7.4 Command GroupsA command group is a set of commands. Commands form some command groups, and then thecommand groups are assigned to users with different authorities for administration management.A command can be in multiple command groups.

The system defines 32 command groups as follows:

l G_0 to G_14, and G_31: default command group

l G_15 to G_30: custom command group

Table 6-2 describes these command groups.

Table 6-2 Command group description

Command Group Function Remarks

G_0 Guest group Predefined MML commandgroups. The commands inthese groups can be queriedbut cannot be modified.

G_1 Alarm query

G_2 Alarm modification

G_3 Performance query

G_4 Performance creation

G_5 Performance modification

G_6 Equipment query

G_7 Equipment modification

G_8 Configuration query

G_9 Configuration modification

G_10 Trace query

G_11 Trace creation

G_12 BNET query

G_13 BNET modification


System Principle


Issue 03 (2009-05-27)

Command Group Function Remarks

G_14 SGSN informationmanagement

G_15 to G_30 Custom group The commands in thesegroups can be queried andmodified.

G_31 System group Predefined MML commandgroups. The commands inthese groups can be queriedbut cannot be modified.

6.8 User or Interface TracingTracing function is used in the routine maintenance for the SGSN. By tracing the information,you can locate where the fault occurs in the service procedure. After the data is configured forthe SGSN, you can establish tracing to verify if the signaling links are normal, and thus judgewhere the fault occurs.

Tracing consists of two types: user tracing and interface tracing.

Figure 6-9 shows the procedure for user tracing or interface tracing.



6-17

Figure 6-9 Procedure for user tracing or interface tracing

Tracing module

Tracingcreation

FAM

UOMU

Tracingreport

LMT

LAN

FAM

Service module

Service board

FAM

Service module

Service board

Tracing report

To carry out user tracing or interface tracing, perform the following steps:

1. The operator sends the MML command to create the task through the maintenance console.

2. The tracing task resolves the command and sends the tracing message to the service modulein the board.

3. After processing the message, the service module sends it to the tracing module.

4. After processing the message, the tracing module sends it to the maintenance console.

6.9 Log ManagementThe log management subsystem records the generated messages when the system runs and savesthe messages to the UOMU hard disk, and thus facilitates problem location and systemmaintenance.

The SGSN9810 saves the following logs:

l Operation log


System Principle


Issue 03 (2009-05-27)

The operation log contains the records of all LMT operations and other related information,including: user name, user ID, IP address of the LMT, command, command execution dataor time, execution result.

NOTE

You can execute LST LOG to query the user operation log.

l System logWhen the system runs, the system log records important events, such as startup, reset, andload to facilitate the maintenance personnel to locate the problems.

l Fault logWhen serious abnormity occurs in the system, the fault log records the on-site informationcaptured by the monitoring module. The information includes abnormal task information,time when abnormity occurs, and call stack for function.

l FTP logThe FTP log records the user's operation on the files in the UOMU hard disk through theFTP. The recorded information includes login time, login IP address, user name, andoperation files.

NOTE

You can execute LST LOG to query the user operation log.

All the logs discussed above can be obtained from UOMU hard disk through the FTP.

6.10 External Maintenance InterfaceThe O&M subsystem acts as a bridge to connect the SGSN with users, so the subsystem mustprovide various network management systems with the interconnected interfaces. Currently, theSGSN can provide the command input and output interface and SNMP interface.

The network management devices that directly connected with the SGSN include the LMT,M2000, and network management system providing the SNMP interface. The SGSN connectswith the LMT and M2000 through the uniform input and output interfaces for MML commands.

Figure 6-10 shows the external O&M interfaces of the SGSN.



6-19

Figure 6-10 External O&M interfaces of the SGSN

MML command/report interface

SNMPinterface

LMT

LAN

M2000

MML command/report interface

SNMPManager

SGSN

6.10.1 Command Input and Output InterfaceAll the O&M management on the SGSN is realized through MML commands with a uniformformat.

6.10.2 SNMP InterfaceThe SGSN adopts the SNMP interface to realize alarm and performance statistics functions.

6.10.3 SSHThe SGSN supports SSH 2.0 applied to the LMT and UOMU to guarantee security of networkaccess.

6.10.1 Command Input and Output InterfaceAll the O&M management on the SGSN is realized through MML commands with a uniformformat.

Command name: parameter name 1 = parameter value 1, parameter name 2 = parameter value2, …, parameter name N = parameter value N

The command delivered by the network management system is sent to the BAM on the UOMUthrough the character strings. The BAM resolves the character strings and extract the specificcommand and parameter values.

Likewise, command output adopts a uniform format for output reports. After encapsulating thecommand execution result to a report with a uniform format, the BAM sends the report to thenetwork management system. Then the network management system resolves the text report toobtain the execution result and query result.


System Principle


Issue 03 (2009-05-27)

6.10.2 SNMP InterfaceThe SGSN adopts the SNMP interface to realize alarm and performance statistics functions.

Figure 6-11 shows the structure and flow of SNMP.

Figure 6-11 Structure and flow of SNMP

SNMP ManagerSGSN (SNMP Agent)

Request/Response

Trap

The network management system (NMS) and agent transfer management information bysending messages to each other. The messages have the following types:

l Get Request message: to obtain the value of the specified management variable

l GetNext Request message: to continuously obtain a batch of values of the managementvariable

l Get Response message: to meet the requirement and return the required value or the errortype

l Set Request message: to set the specified management variable

l Trap message: to actively send information from the managed equipment to the NMS inemergency

The SGSN adopts the SNMP interface to realize alarm and performance statistics functions. Thealarm management function is realized through the Trap message and the performancemanagement function through the Get Request, GetNext Request, and Get Response messages.

6.10.3 SSHThe SGSN supports SSH 2.0 applied to the LMT and UOMU to guarantee security of networkaccess.

When a user on an insecure network telnets the SGSN, the secure shell (SSH) feature offerssecurity guarantee and powerful authentication to protect the SGSN from attacks, such as IPaddress fraud and the interception of the plain text password.

The SGSN supports the SSH applied between the LMT and UOMU to ensure securely visitingthe network The SGSN can connect with multiple SSH clients.

The SSH client function allows users to establish SSH connections with the SGSN that supportsthe SSH server, as shown in Figure 6-12.



6-21

Figure 6-12 Establishing an SSH channel between the SGSN and LMT

The communication between the server and the client follows six phases to accomplish theauthentication security connection of SSH:

l Negotiation for version

l Negotiation for algorithm

l Key exchange

l Identity Authentication

l Session request

l Interactive session

SSH can implement secure remote access on insecure networks. It has the following advantages:

l SSH supports RSA authentication mode. In RSA authentication, SSH implements securekey exchange by generating public and private keys, and thus realizes the whole secureprocess of sessions.

l SSH supports three data encryption standard: advanced encryption standard (AES), dataencryption standard (DES) and 3DES.

l SSH provides encryption to the transmitted data to guarantee data security and reliability.


System Principle


Issue 03 (2009-05-27)

Index

Aalarm management, 6-10

Bboard list, 1-6bus

H.110 Bus, 2-4serial port bus, 2-6shared resource bus, 2-3subracks, 2-3

Ccharging system

generating a CDR, 5-4location, 5-2processing and sending a CDR, 5-6

clock synchronization subsystemclock control Ppart, 2-18distribution part, 2-16interface part, 2-15overview, 2-12structure, 2-14

configuration management, 6-5

Eequipment monitoring subsystem

equipment room environment monitoring, 2-19fan , 2-18

external maintenance interfacecommand input and output interface, 6-20SNMP interface, 6-21SSH, 6-21

Ffan monitoring, 2-18

GGb interface subsystem

procedure, 4-9

structure, 4-7Gn/Gp interface subsystem

DNS resolution, 4-21Gn/Gp signaling process, 4-20NTP synchronization, 4-22structure, 4-16user data forwarding, 4-18

Hhardware

board, 1-6clock synchronization subsystem, 2-12equipment monitoring subsystem, 2-18power supply subSystem, 2-7structure, 1-3subrack, 1-5

Iinternal communication subsystem

procedure , 3-12structure, 3-11

IP routing subsystemprinciple, 4-5structure, 4-3

Iu interface control plane subsystemstructure, 4-11

Iu interface signaling subsystemprocedure, 4-14

OO&M system

alarm management, 6-10configuration management, 6-5external maintenance interface, 6-19log management, 6-18performance measurement, 6-7query and control, 6-13security management, 6-14

HUAWEI SGSN9810 Serving GPRS Support NodeSystem Principle Index


i-1

Pplatform management subsystem

startup management, 3-6switchover management, 3-7

platform systeminternal communication subsystem, 3-11location, 3-2platform management subsystem, 3-3

power supply subsystemmonitoring, 2-10structure, 2-7

Ssecurity management

command groups, 6-16domain management, 6-14user authorities, 6-15user name and password, 6-15

service systemGb iInterface subsystem, 4-7Gn/Gp interface subsystem, 4-16IP routing subsystem, 4-3Iu interface control plane subsystem, 4-11signaling subsystem, 4-23typical data processing procedure, 4-28

signaling subsystemprocedure, 4-26structure, 4-23

softwarecharging system, 1-11O&M system, 1-11platform system, 1-10service system, 1-10structure, 1-8

startup management, 3-6structure

hardware, 1-3software , 1-8

subrackbus, 2-3structure, 1-5

switchover management, 3-7

IndexHUAWEI SGSN9810 Serving GPRS Support Node

System Principle

i-2 Huawei Proprietary and ConfidentialCopyright © Huawei Technologies Co., Ltd.

Issue 03 (2009-05-27)

Documents

SGSN Principles(How Does It Works)