45312028 1 GPRS Fundamental Training

Huawei Confidential. All Rights Reserved

OMP000001 GPRS Fundamental

ISSUE 2.0

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1 Internal Use

GPRS principle is the basic part of the whole system and the later products learning. This slide will help us to understand the GPRS system networking and some important procedure.



2 Internal Use

objectobject

Upon completion of this course, you will be able to:¦ Describe the GPRS networking structure

¦ Know the GPRS mobility management procedure

¦ Know the GPRS session management procedure



3 Internal Use

References References

q 3GPP protocol 23060





4 Internal Use

ChapterChapter 1 GPRS Network Structure1 GPRS Network Structure

Chapter 2 Mobility Management

Chapter 3 Location Management

Chapter 4 Session Managment



5 Internal Use

GPRS Network StructureGPRS Network Structure

FR

EIREIRHLRHLRSMS-GMSCSMS-IWMSCSMS-GMSCSMS-IWMSC

MSC/VLRMSC/VLR

BSSBSS

UTRANUTRAN

SGSNSGSN

SGSNSGSN

GGSNGGSN

BGBG

CGCG

TETEPDN

SS7

ATM

DDN

ISDN

Ethernet.etc

GPRSBackbone

Gs Gd Gr Gf Gc

Gb

Iu

Um

Um

Gp

Gi

Gn

Gn

ATM Ga

SCPSCP GMLCGMLC

Ge Lg

Ga



6 Internal Use

GPRS Network StructureGPRS Network Structureq Some Abbreviation

¦ GPRS[General Packet Radio Service

¦ BSS[Base Station Subsystem

¦ UTRAN[UMTS Terrestrial Radio Access Network

¦ SGSN[Service GPRS Support Node

¦ GGSN[Gateway GPRS Support Node

¦ CG[Charging Gateway

¦ BG[Bordering Gateway

¦ PDN[Packet Data Network



7 Internal Use

GPRS Network StructureGPRS Network Structureq Some Abbreviation

¦ MSC/VLR

[Mobile Switch Center/Visitor Location Register¦ SMS-GMSC

[Gateway MSC For Short Message Service¦ SMS-IWMSC

[Short Message Service Interworking MSC¦ SCP

[Service Control Point¦ GMLC

[Gateway Mobile Location Center¦ HLR

[Home Location Register¦ EIR

[Equipment Identity Register



8 Internal Use

Chapter 1 GPRS Network Structure






9 Internal Use

GMM (GPRS Mobility Management)GMM (GPRS Mobility Management)

q Function of the Mobility Management¦ The Mobility Management (MM) activities related to a subscriber are

characterised by one of three different MM states. In A/Gb mode, the

MM states for a GPRS subscriber are IDLE, STANDBY, and READY.

Each state describes a certain level of functionality and information

allocated.

¦ keep track of the current location of an MS within the PLMN or within

another PLMN



10 Internal Use

GMM (GPRS Mobility Management)GMM (GPRS Mobility Management)

q GMM specific procedures¦ Attach procedure

¦ RAU and periodic RAU

¦ Detach

q GMM common procedures¦ P-TMSI reallocation procedure

¦ Authentication procedure

¦ Identification procedure



11 Internal Use

Mobility Management Timer FunctionMobility Management Timer Function

q Periodic RA Update Timer Function¦ Monitors the periodic routing area update procedure in the MS¦ Upon its expiry, the MS shall start a periodic routing area update procedure.¦ The length of the timer is set in SGSN; The value of the timer is sent to MS

in attach accept message or routing update accept messageq Mobile Reachable Timer Function

¦ Upon the expiry of this timer, the MS is detached¦ This is reset and started when the state returns to STANDBY ¦ The timer shall be slightly longer than the periodic RA update timer used by

an MS¦ The length of the timer is set in SGSN

q Purge Timer Function¦ Allows the SGSN to inform the HLR that it has deleted the MM and PDP

contexts of a detached MS.¦ The purge timer is set longer than the mobile reachable timer



12 Internal Use

2G Network States Transition2G Network States Transition

PDU transmission

Implicit Detachor

Cancel Location

GPRS Attach

READY timer expiryorForce to STANDBY

GPRS Detach GPRS Attach

PDU reception

GPRS Detachor

Cancel Location

MM State Model of MS MM State Model of SGSN

IDLE

READY

STANDBY

IDLE

READY

STANDBY

READY timer expiryorForce to STANDBYorAbnormal RLC condition



13 Internal Use

Attach ProcedureAttach Procedure

q Function

¦ An MS shall perform a GPRS Attach to the SGSN in order to obtain access

to the GPRS services. It shall perform a GSM GPRS Attach procedure.

¦ Only MS can initiate the Attach Procedure



14 Internal Use


(IMSI or PTMSI+RAI) (PTMSI)

(IMSI)

(Identity Type = IMSI)

(IMSI)



15 Internal Use




16 Internal Use


q Results after any attach procedure¦ SGSN get subscriber data from HLR¦ HLR recorded the MS’s serving SGSN number¦ SGSN and MS create MM context for the MS

q MS can request Session Management services



17 Internal Use

Detach ProcedureDetach Procedure

q Function ¦ The GPRS Detach procedure allows an MS to inform the network that it

does not want to access the SGSN-based services any longer¦ The GPRS Detach procedure allows the network to inform an MS that it

does not have access to the SGSN-based services any more

q The following three entity can initiate the detach procedure¦ MS¦ SGSN¦ HLR



18 Internal Use

Detach Procedure (MS Initiation)Detach Procedure (MS Initiation)

2. Delete PDP Context Response

1. Detach Request

2. Delete PDP Context Request

3. Detach Accept

MS BSS/UTRAN GGSN SGSN

4. PS Signalling Connection Release



19 Internal Use

Detach ProcedureDetach Procedure

q Results after any detach procedure¦ The SGSN shall not service the detached MS, unless reattach¦ The MS is in idle state

q The MS is detached either explicitly or implicitly:¦ Explicit detach: The network or the MS explicitly requests detach¦ Implicit detach: The network detaches the MS, without notifying the MS, a

configuration-dependent timer after the mobile reachable timer expired, or after an irrecoverable radio error causes disconnection of the logical link.



20 Internal Use

Purge FunctionPurge Function

q Function¦ The Purge function allows an SGSN to inform the HLR that it has deleted

the MM and PDP contexts of a detached MS

q After the MS detach from the network:¦ The SGSN may delete the MM/PDP context immediately¦ the SGSN may keep the MM/PDP context for some time of the detached

MS



21 Internal Use

Purge Function Purge Function (clear or remove)(clear or remove)

1. Purge MS

2. Purge MS Ack

SGSN HLR



22 Internal Use

Authentication Function (2G)Authentication Function (2G)

q Function¦ "GSM authentication" implies authentication of the MS by the network

and establishment of a new GSM ciphering key (Kc) agreement between

the SGSN and the MS.

¦ "GSM authentication" ensure that the user is authorised to use the

particular network services

¦ Each triplet contains RAND, SRES and Kc¦ Authentication triplets are stored in the SGSN



23 Internal Use

Authentication Function (2G)Authentication Function (2G)

1. Send Authentication Info

2. Authentication and Ciphering Request 1. Send Authentication Info Ack

2. Authentication and Ciphering Response

MS BSS/UTRAN HLRSGSN



24 Internal Use

Identity CheckIdentity Check

q Function¦ Get IMSI from MS

¦ Check the IMEI



25 Internal Use

Identity CheckIdentity Check

1. Identity Response 2. Check IMEI

1. Identity Request

2. Check IMEI Ack

MS BSS/UTRAN EIRSGSN



26 Internal Use

PP--TMSI ReallocationTMSI Reallocation

2. P-TMSI Reallocation Complete

1. P-TMSI Reallocation Command

MS BSS/UTRAN SGSN



27 Internal Use

PP--TMSI ReallocationTMSI Reallocation

q Function¦ The SGSN may reallocate the P-TMSI at any time

¦ The reallocation procedure can be performed by the P-TMSI

Reallocation procedure

¦ The P-TMSI can be included in the Attach or Routeing Area Update

procedures.



28 Internal Use







29 Internal Use

Location ManagementLocation Management

q Function¦ A mechanism that allows the system to keep track of the location

information of MS¦ A mechanism that allows the system to keep synchronization of the

states of MS‘s MM context



30 Internal Use

Layered Location Management Mode (2G)Layered Location Management Mode (2G)

•SGSN

•HLR

•BSS

•MS

•SGSN number

•ready state: cell number

•Standby state: RAI



31 Internal Use

RouteingRouteing Area Update ProcedureArea Update Procedure

MS

RAI 2 RAI 4

SGSN SGSN

RAI 1 RAI 3

cell

Intra SGSN-RAU

Inter SGSN -RAU

Gn



32 Internal Use

RouteingRouteing Area Update ProcedureArea Update Procedure

q RAU procedure will happen in the following two case:¦ MS entered a new Route Area

¦ Periodic RAU ( after periodic timer expires)

q Inter-SGSN RAU

¦ The new SGSN find the old SGSN from the old RAI

¦ Old SGSN stop downlink signaling, transfer MM context and PDP

context to new SGSN

¦ Tunnelling N-PDU to the new SGSN

¦ Update PDP context and subscriber data



33 Internal Use







34 Internal Use

Session ManagementSession Management

q Function ¦ Manage the connection between MS, SGSN and GGSN and

allocate system resource for the service transmission

q Important Procedure¦ PDP Context Activation¦ PDP Context Modification¦ PDP Context Deactivation



35 Internal Use

Session ManagementSession Management

DNS

BTS

SGSN

MS

DNS

BSC

GGSN (B)BackboneBackboneDNS

ISP BISP B

ISP AISP A

Corp.Network

Corp.Network

GGSN (A)

••APNAPN--NINI

••APN APN ＝＝ GGSN IP addressGGSN IP address

••APNAPN--NINI



36 Internal Use

PDP ContextPDP Context

q PDP Context ¦ The PDP context is Packet Data Protocol context

¦ PDP context contains all the information needed to transfer user data

between MS and GGSN.

¦ The context includes parameters such as Routing, QoS (Quality of

Service), Charging ID etc.

¦ PDP context exists in MS, SGSN, GGSN



37 Internal Use


XXThe quality of service profile subscribed.QoS Profile Subscribed

XXSpecifies whether the MS is allowed to use the APN in the domainof the HPLMN only, or additionally the APN in the domain of the VPLMN.

VPLMN Address Allowed

XXThe IP address of the GGSN currently used.GGSN Address in Use

XTunnel Endpoint Identifier for the Iu interface.TEID for Iu

XXTunnel Endpoint Identifier for the Gn and Gp interfaces.TEID for Gn/Gp

XXTransaction Identifier.TI

XXNetwork layer Service Access Point Identifier.NSAPI

XXThe APN currently used. This APN shall be composed of the APNNetwork Identifier and the APN Operator Identifier.

APN in Use

XXThe APN received from the HLR.APN Subscribed

XXPDP address, e.g. an IP address.PDP Address

XXPDP type, e.g. PPP or IP.PDP Type

XXPacket data protocol state, INACTIVE or ACTIVE.PDP State

XXIndex of the PDP context.PDP Context Identifier

Each MM context contains zero or more of the following PDP contexts:



38 Internal Use


XThe IP address of the RNC currently used.RNC Address in Use

XXThe charging characteristics of this PDP context, e.g. normal, prepaid, flat-rate, and/or hot billing.

PDP Context Charging Characteristics

XXCharging identifier, identifies charging records generated by SGSN and GGSN.

Charging Id

XSequence number of the next uplink in-sequence PDCP-PDU expected from the MS.

PDCP-SNU

XSequence number of the next downlink in-sequence PDCP-PDU to be sent to the MS.

PDCP-SND

XXGTP-U sequence number of the next uplink N-PDU to be sent to the GGSN.

GTP-SNU

XXGTP-U sequence number of the next downlink N-PDU to be sent to the MS.

GTP-SND

XSNDCP sequence number of the next uplink N-PDU expected from the MS.

Receive N-PDU Number

XSNDCP sequence number of the next downlink N-PDU to be sent to the MS.

Send N-PDU Number

XThe aggregate BSS quality of service profile negotiated for the packet flow that this PDP context belongs to.

Aggregate BSS QoS Profile Negotiated

XPacket flow identifier.Packet Flow Id

XThe RLC/MAC radio priority level for uplink user data transmission.Radio Priority

XXThe quality of service profile negotiated.QoS Profile Negotiated

XXThe quality of service profile requested.QoS Profile Requested



39 Internal Use

MM Context and PDP ContextMM Context and PDP Context

HLR

SGSNBSC

or RNC

MS GGSNGnGb/ IuUu

PDP context #2

.

.

PDP context #1

MM context

PDP context #2

.

.

PDP context #1

MM context

PDP context #2

.

.

.

PDP context #1



40 Internal Use

Important Concept __ APNImportant Concept __ APN

q APN structure: APN_NI+APN_OI

cmnet.mnc<MNC>.mcc<MCC>.gprs

APNNetwork ID

APNOperator ID

•Operator ID : fixed extension, must end with “.gprs”

•Network ID shall not end with “.gprs”



41 Internal Use


MS SGSN

GGSN1

GGSN2

GGSN3

DNS

APN1

APN2

APN3

APN1=GGSN1 IP

APN2=GGSN2 IP

APN3=GGSN3 IP

APN

APN GGSN IP

APN1

APN2

APN3



42 Internal Use


SGSN

MS

SGSN

MS

•internet

GGSN GGSN

Roaming

APN:CMNET

•GuangDong province

q General APN



43 Internal Use


SGSN

MS

SGSN

MS

GGSN GGSN

Roaming

APN:test.xy

VPN tunnel

Province 1

q Area APN

Province 2



44 Internal Use

Important Concept __ PDP StateImportant Concept __ PDP State

Deactivate PDP Contextor

MM state change to IDLEor PMM-DETACHED

Activate PDPContext

INACTIVE

ACTIVE

q PDP state¦ inactive：cannot transmit data ¦ active：can transmit data



45 Internal Use

Important Concept __ PDP Type and PDP AddressImportant Concept __ PDP Type and PDP Address

q PDP Type¦ IPV4 ¦ IPV6¦ PPP

q PDP Address¦ Static IP

[Public IP[Allocate by the operator

¦ Dynamic IP[Private IP[Allocate by GGSN, DHCP or Radius



46 Internal Use

Important Concept __ Important Concept __ QoSQoS

q QoS is quality of service

q It is a group of parameters that can define the network ability, such

as the bit rate for downlink or uplink data transmission and the

reliability class and so on

q It is end to end concept



47 Internal Use

Activation ProcedureActivation Procedure

q PDP context activation procedure¦ To establish a PDP context between the MS and the SGSN, the GGSN

¦ The first PDP context for a given PDP address and APN



48 Internal Use

PDP Active Procedure (2G)PDP Active Procedure (2G)

2G-GGSN

9. Activate PDP Context Accept

4. Create PDP Context Response

4. Create PDP Context Request

1. Activate PDP Context Request

2G-SGSNBSS

2. Security Functions

MS

7. BSS Packet Flow Context Procedures

C1

C2

3. Invoke Trace



49 Internal Use

Handle in MSHandle in MS

q MS start and send “Active PDP context request” to SGSN¦ Provide QoS parameter

¦ Provide a APN-NI

¦ Provide a static IP or null

q Receive ACCEPT from SGSN¦ If the QoS not accept by MS, then starts deactive procedure.



50 Internal Use

Handle in SGSNHandle in SGSNq Check subscriber data q APN selection

¦ According to TS 23.060 ¦ default APN,APN provide from MS and the APN subscribed in HLR¦ APN-NI.APN-OI

q Interrogate DNS¦ Hostfile/Cache/DNS server

q QoS negotiation¦ QoS provided from MS, default QoS ,QoS subscribed in HLR

q Send message “create PDP context request” to GGSNq Send message “active PDP context accept” to MS

¦ Dynamic IP address¦ QoS

q RAB assignment



51 Internal Use

Handle in GGSNHandle in GGSN

q Check the APN provided by SGSNq QoS negotiationq Allocate a dynamic IP to the MS q Allocate a charging ID for the PDP contextq Return a CREATE PDP CONTEXT ACCEPT message to SGSN

¦ Dynamic IP¦ QoS¦ Charging ID¦ Other information

q Update PDP context



52 Internal Use

SummarySummary

q In the whole GPRS fundamental, you should remember some important concept and the basic signalling procedure

SummarySummary



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45312028 1 GPRS Fundamental Training