Introduction into Mobile Core Network

WebEx Sunday Session24 March 2013

• Goal– Introduction into 2G/3G and 4G core

network element in Telco technology, particular for non-Telco person.

– Overview of call establishment process– Experience sharing of 4G EPC project

delivery from existing Mobile Network Operator.

• What is not covered here…– Wireless and radio related part.– Detail and ‘deep dive’ of each network

element.– Detail procedure for call establishment.

• Disclaimer– All material presented here is solely for non-profit

educational purpose.

About this presentation

Node and Interface in Telco

• What is a Node ?Node is a network component that is capable of receiving, sending or forwarding electronic information over the designated communication link. For example BSC, RNC, SGSN, MSC, HLR.Known as Network Element too..

• What is an Interface ?In telecommunication, an interface is a logical link connection or a reference point, between two components in telecommunication infrastructure, for example, Gn interface is a reference point between SGSN and a GGSN.

However, Telecommunication also use term ‘interface’ as a device or program of that enabling a communication between user and a computing device.

2G and 3G Network Architecture

User planeControl plane

SGSN GGSN

Packet Data Networke..g Internet

GiGn

IuPS

Gb

BSC

BTSMS

Abis

RNC

NodeB

MSIub

HLR

SMSC

DNS

RADIUS

DHCP

Charging Centre

NMS / OSS

Service & subscriber management

PCRF

Gx/Gz

Gz/Gs/Gr/Gf/Gd

MGW

MSS/VLR

MGW

MSS/VLR

PSTNOther PLMN

IuCS

Nb

A

Nc

Mc Mc

Packet Core Domain

Circuit Core Domain

Acronym used in Telco..

MS Mobile Subscriber A mobile phone with SIM card

BTS Base Transceiver Station Air interface toward MS in 2G

BSC Base Station Controller Controlling BTS

NodeB n/a Air interface toward MS in 3G

RNC Radio Network Controller Controlling NodeB

MSS Mobile Switching Server Mobility Management for CS Domain

VLR Visitor Location Register Manage temporary subscriber information within an MSS

HLR Home Location Register Manage permanent subscriber Database

MGW Media Gateway Manage user plane traffic

SGSN Support GPRS Service Node Mobility Management for PS Domain

GGSN Gateway GPRS Service Node Session Management , IP address allocation, QoS enforcement, Routing toward internet.

Circuit Switching vs. Packet Switching

• Circuit Switching–Mostly used in the voice call.–Whenever a call is being made, a dedicated logical link needs to be established.–Network resource is allocated and reserved for the subscriber for entire duration of the call.

• Packet Switching–Mostly used in the Packet Data Connection.. . e.g. internet browsing–Whenever an MS sends or receives data, data is organized into packet and each packet has source / destination ID.

Signaling Plane vs. User Plane

• User Plane is the user traffic that contain the conversation between 2 or more user peers.– Carried over the core network as a bearer– Example. Voice call or Browsing data traffic through GPRS

• Control Plane is signaling communication used to control the bearer traffic.– Involving of sending and receiving messages between 2 nodes.– Example. Communication between SGSN and HLR.

A Simplified 2G/3G PS Call Flow…(1/3)

SGSN GGSN

Packet Data Networke..g Internet

GnGb IuPS

BSCRNC

BTS / NodebMS

Abis / Iub

HLR Gn DNS

Attach request..

Attach accepted..

Get info for this subscriber

Herewith the info

I am attached to the

network and want to

browse, by activating

PDP context

Reference : TS 23.060TS 24.008TS 29.060

Internet DNS

Note :All procedures here are simplified for overview

only. Reader should refer to above reference for detail procedures.

1

2

3

4

5

A Simplified 2G/3G PS Call Flow…(2/3)

SGSN GGSN

Packet Data Networke..g Internet

GiGn

Gb -IuPSBSCRNC

BTS / NodebMS

Abis - Iub

HLR Gn DNS

PDP context activation received from MS,

What is the IP address of the GGSN that serving this APN ? ?

Herewith the IP address of GGSN

Create PDP

Context Request

Create PDP Context

accepted

Create PDP context accepted, send this

info to MS

Reference : TS 23.060TS 24.008TS 29.060

Internet DNS

Note :All procedures here are simplified for overview

only. Reader should refer to above reference for detail procedures.

I am attached to the

network and want to

browse , by activating

PDP context

5

6

7

8 9

10

PDP context activation accepted, now browse

towww.google.com.au

11

A Simplified 2G/3G PS Call Flow…(3/3)

SGSN GGSN

Packet Data Networke..g Internet

GiGn

Gb -IuPSBSCRNC

BTS / NodebMS

Abis - Iub

HLR Gn DNS

Reference : TS 23.060TS 24.008TS 29.060

Internet DNS

Note :All procedures here are simplified for overview

only. Reader should refer to above reference for detail procedures.

PDP context activation accepted, now browse

towww.google.com.au

11

12

13

HandoverAction of switching a call in progress from one radio channel to another to secure the continuity of an established call.

The purpose of handover control is to manage the mobility aspect of the Subscriber. This means keeping track of mobile stations (MS) as they move around in the network, and ensuring that their connections are uninterrupted and meet the negotiated Quality of Service requirements.

Move to 4G..???

• Wait…first, let see the widely involvement of IP protocol.

• Protocol used in the control plane messaging has evolved.– Changes in Transport Layer protocol

while keeping all the Application Layer remain unchanged.

– Completely changed at Transport and Application Layer.

• Transport Layer has changed dramatically from legacy protocol toward IP.

User planeControl plane

SGSN

RNCNodeBS4S12 DT

IuR8 3G

BSCBTS 2G SGSNGb R8 2G

General LTE Architecture

GnGn

BSC/RNCPre R8 2G/3G

SGSNBTS/NodeBGbIu

R7 DT

PCRF

Gx

S1-MME

S1-U S6a

HSS

eNodeB

S10MME

LTE

S5PGWSGW

SGi

SGi

S11

S3

SGs MSC

SGiInternet

Operator services

Basic EPS architecture defined in 3GPP TS 23.401

Acronym used in 4G

E-NodeB Air interface toward MS in 4G

MME Mobility Management Entity Mobility Management for 4G, Control Plane only

S-GW Serving Gateway Mobility Management for 4G for User Plane, Handover anchoring .

P-GW Packet Data Network Gateway Routing to Packet Data Network, Session Management, IP address Allocation. Function of P-GW is similar to GGSN in the 2G/3G network

HSS Home Subscriber Server Manage Permanent 4G subscriber data. Evolution of HLR.

Internet has driven operation model…(1/3)

SGSN GGSN

HLR

RNC

TDM

IP / MPLS

ATM

Internet

Operator Network

Multiple network type exist on Mobile Operator Network

Internet has driven operation model…(2/3)

SGSN GGSN

HLR

RNC

TDM

IP / MPLS

ATM

Internet

Operator Network

Driven by internet grows, Telco vendor is developing their product using IP as the transport media.

Internet has driven operation model…(3/3)

SGSN GGSN

HLR

RNC

IP / MPLS

Internet

Operator Network

Driven by internet grows, Telco vendor is developing their product using IP as the transport media. Mobile Operator needs to ‘simplify’ the O&M for many network type. New challenges and opportunities are on-board for IP (IT) and Telco engineer.

Protocol has been changed.. (1/2)

MTP Layer 1

MTP Layer 2

MTP Layer 3

INAP/CAPTUPISUP

BSSAPMAP

SCCP

TCAP

Legacy Gr InterfaceBetween SGSN – HLR Using MAP ApplicationSS7 protocol

Physical Layer

Data Link Layer

IP

SCTP

M3UA

Gr InterfaceBetween SGSN – HLR Using MAP ApplicationSS7 protocol transported over IP

Protocol has been changed… (2/2)

Physical Layer

Data Link Layer

IP

SCTP

Diameter Application

Physical Layer

Data Link Layer

IP

SCTP

M3UA

Gr InterfaceBetween SGSN – HLR Using MAP ApplicationSS7 protocol transported over IP

S6a InterfaceBetween MME – HSS Using Diameter ApplicationRFC 3588TS 29.272

IP is here…

PDCP

RLC

MAC

UE eNB MME

NAS NAS

RRC

SCTP

IP

L2

L1

S1AP

UDP

IP

L2

L1

GTP-Cv2

S-GW

Uu S1-MME S11

RLC

PHY

RRC

PHY

MAC

PDCP SCTP

L2

L1

S1AP

UDP

IP

L2

L1

GTP-Cv2PMIP

IP

PDCP

UE eNB S-GW

UDP

IP

L2

L1

UDP

IP

L2

L1

P-GW

Uu S1-U S5/S8

PHYPHY

PDCP

UDP

L2

L1

UDP

IP

L2

L1

IP

GTP-U

MAC

RLC

GTP-U GTP-U/GRE GTP-U/GRE

RLC

MACUse

r Pla

ne

Cont

rol P

lane

P-GW

UDP

IP

L2

L1

GTP-Cv2PMIP

S5/S8

…and here…

UDP

IP

L2

SGSN / MME

GTP-Cv2

S3/S4/S10/S16

L1

UDP

IP

L2

MME

GTP-Cv2

L1

Cont

rol P

lane

UDP

IP

L2

SGSN

GTP-U

S4/S12

L1

UDP

IP

L2

S-GW

GTP-U

L1

Use

r Pla

neSCTP/TCP

IP

L2

MME

Diameter

S6a/S6d/S13

L1

SCTP/TCP

IP

L2

HSS/EIR

Diameter

L1

Cont

rol P

lane

Reference : TS 29.281TS 23.401

…and everywhere…

VRF AVRF BVRF CVRF D

VRF S5VRF S1uVRF OAMVRF SGi

PEP-GW

•IP addressing scheme ? Private/public ? •Running OSPF between Node and PE• Area 0 or non-backbone ?• Stub or totally stub ? NSSA ?

•or should BGP being used ??

Example : VRF Concept

A wake up call for Telco Engineer !!!

Multiple OSPF process

ISP A

ISP B

Costumer C

192.168.1.1/24

192.168.2.1/24

192.168.3.1/24

192.168.4.1/24

Client Role Server Role

Primary Path

Secondary Path

• Based on IETF - RFC 4960• Application always use 2 IPs from different subnet for each node.• Whenever there is a failure in primary path, the client and server automatically

switch the traffic into secondary path.• Applied for most signaling traffic, such diameter, Sigtran.• Telco engineer to make sure that Client – Server communicate correctly.• IP engineer to make sure that there is a path diversity within IP network and there is

NO unseen single point of failure may happen.

…While in telecommunication has another view about multihoming..

Customer – Provider

Multihoming Concept

A Simplified PS Call Flow with 4G…(1/2)

MME

S-GW

Packet Data Networke..g Internet

SGi

S11S1u

eNodeBMS

S1

HSS DNS

Attach request..

Get info for this subscriber

Herewith the info

I am attached to the network and

want to browse to www.google.com.

au

What is the S-GW IP Address ?What is the P-GW IP Address ?

Herewith the IP Addresses

Create Session Request with IP Address of S-GW and P-GW

Create Session Request response (Accept)

P-GW

Create Session Request with IP Address of P-GW

Create Session Request response (Accept)

Create Session Request response (Accept)

S5/S8

Reference : TS 29.281TS 23.401TS 29.274

Note :All procedures here are simplified for overview

only. Reader should refer to above reference for detail procedures.

1

2

3

4

5

6

7

8

9

10

11

A Simplified PS Call Flow with 4G… (2/2)

MME

S-GW

Packet Data Networke..g Internet

SGi

S11S1u

eNodeBMS

S1

HSS DNS

I am attached to the network and

want to browse to www.google.com.

au

P-GWS5/S8

Reference : TS 29.281TS 23.401TS 29.274

Note :All procedures here are simplified for overview

only. Reader should refer to above reference for detail procedures.

11 12

Internet DNS

13

LTE QoS Concept Overview• Admission Control

– Prioritize bearers based on QoS parameter– Protect network element in case of congestion or overload.

• Traffic Control– Traffic classification (queuing, scheduling)– Traffic policing and shaping

EPC Project Delivery• Client : one of live mobile operator • Duration : Jan 2012- November 2012• Involving 3 areas of expertise :

– PS Core– CS Core – IP

Prepare

Plan

Design

Implement

Operate

Optimization

User planeControl plane

Network Assessment : Current 2G/3G Mobile Packet Core

S6a

S1-MME

S1-UeNodeB

S10MME

LTE S5

PGWSGW

S11

SGs MSC

SGi

GGSN

GnGn

BSC/RNC

Pre R8 2G/3G

SGSNBTS/NodeBGbIu

R7 DT

Internet

Operator services

HLR/HSS

Gi

Gr

Project Delivery: EPC Node Commissioning and IntegrationNetwork Target : LTE & 2G/3G interworking

• It is a new technology..– New network elements, protocols and

procedures.– Everyone involve may have their own

interpretation during planning, commissioning and integration.

– Limited reference from available production network.

– Always refer to International Standard. 3GPP, RFC and GSMA.

Lessons learned and Challenges...

It is all IP..– A complexity of client MPLS network.– Design and Planning is taking an

important step.– Requires an intensive collaboration

work with IP team. – Things worth to note…

• L1 implementation. Wrong cable positioning• VLAN and IP addressing, public/private ??• Pay attention into any node limitation : port type,

MTU, active/standby behavior, Load Balance concept, Client-Server role

Diameter Routing Planning..

MME MME

HSS EIR

MME MME

DRA

HSS EIRHSS HSS HSS

Roaming Partner /GRX

DRA

Without DRADRA=Diameter Routing Agent With DRA

Some screenshots from 4G handset

Some speed test in various location.

Upcoming technical challenges with LTE

More InformationTechnical Specification and Standard. Readable and downloadable for

public • www.3gpp.org/specification-numbering• www.ietf.org• http://www.gsma.com/newsroom/technical-documents

EPC Product Knowledge. Also readable and downloadable for public • http://www.cisco.com/en/US/products/ps11072/products_installatio

n_and_configuration_guides_list.html

Further discussion

• Parakontel • Indocisco

…ready to ‘take-off’ now ?

…then please fasten your seatbelt…

Thank You….

Images Creditshttp://wallpoper.com/wallpaper/board-circuit-253188http://forzamotorsport.net/en-US/fm4/tracks.aspx?t=Circuit_de_Catalunyahttp://www.certshelp.com/blog/wp-content/uploads/2012/10/ip-address.jpghttp://coachgiorgio.com/wp-content/uploads/2011/05/teamwork4.jpg

Further discussion.