Gprs 3 Traffic w

1 GPRS/EDGE INTRODUCTION

GPRS Traffic ManagementGPRS Traffic Management


Module objectivesThis module enables the participant to:• Explain the mobility management functions in GPRS:

GPRS attach/detach, cell update, routing area update• Explain the session management functions in GPRS:

PDP context activation• Explain the difference between idle, ready, and

standby MS states and their relation to the different MM functions

• Explain addressing in GPRS• Describe charging in GPRS.


What sort of procedures are needed?• MS switches on for the first time. • MS indicates that it is switched on and ready (GPRS

attach).• MS indicates that it is switched off (GPRS detach).• MS indicates that it wants to transmit data (PDP context

activation).• MS indicates stop data transmission (PDP context

deactivation).• MS moves from one part to another of a service area

(Cell update and RA update procedure).• MS may roam into another networks service area

(Roaming).• etc.


What is traffic management?Traffic management procedures are subdivided into two

areas:1. Mobility management

• Procedures that take care of the mobility of the user such as the GPRS attach are called GPRS Mobility Management (GMM).The GMM procedures are similar to the mobility management for circuit switched users.

• Examples: GPRS attach, GPRS detach, cell update, intra-SGSN routing area update

2. Session management• Procedures that handle the GPRS MS connection

management to the external data networks are called Session Management (SM).

• Examples: PDP context activation


Type of info What info Where

Identity IMSI

TMSI

IP address

SIM, HLR, VLR, SGSN

SGSN, MS

MS, SGSN, GGSN

Location VLR address

Location area

Serving SGSN

Routing area

HLR

SGSN, VLR

HLR, VLR

SGSN

Services Basic services, supplementaryservices, circuit switched bearerservices, GPRS serviceinformation

Basic services, supplementaryservices, CS bearer services

GPRS service information

HLR

VLR

SGSN

Authentication data Ki, algorithms

Triplets

SIM, AC

VLR, SGSN

Subscriber information, information elements, and location


What is a routing area?

RA-2

RA-1

RA-3


Routing area

SGSN-1

BSC-1RA-1 RA-3

SGSN-2

BSC-2

RA-2

LA-1 LA-3


MS states

RA-1

VLR-1

HLR

SGSN-1BSC

LA-1


MS Idle

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLRSGSN

IMSILAISGSN ?

IMSI ?RA ?Cell ?

LA-1


MS Ready

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLR VLR-1SGSN SGSN-1

IMSI 244...LAI LA-1SGSN SGSN-1

IMSI 244...RAI RA-1CellCell cellcell--11

LA-1


MS Standby

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLR VLR-1SGSN SGSN-1

IMSI 244...LAI LA-1SGSN SGSN-1

IMSI 244...RAI RA-1CellCell ??????????

LA-1


GPRS Attach

PDU transmission

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

STANDBY timer expiryor

Cancel Location

READY timer expiryorForce to STANDBY

READY timer expiryorForce to STANDBYorAbnormal RLC condition

STANDBY timer expiry


GPRS attach (0)

RA-1

HLR

SGSN-1

BSC

LA-1


GPRS attach (1) (First time in PLMN)

RA-1

HLR

SGSN-1

BSC

LA-1

1

2a 2b

(1) MS Requests GPRS attach. (2a) The SGSN requests subscriber identity. (2b) The MS sends its IMSI.


GPRS attach (2) authentication(3a) SGSN requests triplets

from AC. (First time in PLMN).

(3b) The AC generates the triplets (RAND, SRES, Kc) and hands them to the SGSN.

(3c) SGSN sends an authentication request to the MS (along with RAND).

(3f) The SIM calculates SRES’ and sends it to SGSN.

(3g) SGSN verifies (SRES=SRES’).

RA-1

HLR/AC

SGSN-1

BSC

LA-1

3f

3a

3b

3c


GPRS attach (3) IMEI check

RA-1

EIR

SGSN-1

BSC

LA-1

4a

4b

4c

4d(4a) SGSN asks for MS IMEI.

(4b) MS sends the IMEI.(4c) SGSN sends a Check

IMEI message to the EIR.

(4d) EIR replies with a Check IMEI ack that will include the list type where the IMEI was found (unknown, white, grey, or black).


GPRS attach (4)

RA-1

HLR

SGSN-1

BSC

LA-1

5a

5b

5c

5d

6a

6b

(5a) SGSN sends Update location message to HLR with subscriber IMSI.

(5b) HLR responds by giving subscriber data to the SGSN.

(5c) SGSN acknowledges that it has received the subscriber data ok.

(5d) HLR ends the transaction with an Update Location ack.

(6a) SGSN accepts the GPRS attach and sends MS a new P-TMSI.

(6b) MS acknowledges that it has received the new P-TMSI.


P-TMSI and TLLI• P-TMSI = Packet Temporary Mobile Subscriber Identity

• SGSN allocates P-TMSI• A new P-TMSI is allocated for each GPRS attach• P-TMSI is an alias for the GPRS MS just like the TMSI • P-TMSI is only valid in a routing area (RA)

• TLLI (Temporary Logical Link Identity) derived from P-TMSI • TLLI is used as identifier for connection between MS and

SGSN• TLLI used as MS’s address for transmission between

SGSN-MS• Only SGSN and MS know relationship between TLLI and

IMSI


What happens after a GPRS attach?• After GPRS attach, SGSN starts tracking location of the

MS • MS can send and receive SMS, but no other data• To transfer other data it first has to activate a PDP

context• When the subscriber wants to end a connection to the

GPRS network, the GPRS detach is used• GPRS detach changes state of MS to Idle and mobility

management context in SGSN (and in the MS) is removed• MS normally initiates GPRS detach, but it can also be

initiated by the network if mobile reachable timer expires


What is location management?• Subset of mobility management procedures

• Used to handle the hanging of a cell or a routing area

• What types of location management procedures are needed?• Movement between cells

• Cell update• Movement between RAs

• Routing area update • Movement between LAs• Checking if MS is still active

• Periodic routing area update is used for checking that a MS that has not done any RA updates for some period of time is still reachable


SGSN-1

BSC-1

RA-1

Old cell New cell

What is cell update?• Also called cell update cell reselection• Occurs when MS changes cell within RA in Ready mode

• Compared to handover in GSM


What is routing area update?• When the MS changes cells between the different routing

areas, it performs a routing area update. • There are two types of routing area updates:

1. Intra-SGSN routing area update • If new RA is managed by same SGSN, an intra-SGSN

routing area update is performed. The old PAPU forwards user packets to the new PAPU.

2. Inter-SGSN routing area update • One SGSN can manage many routing areas. If the new

routing area is managed by a different SGSN, an inter-SGSN routing area update is performed.


Intra-SGSN routing area update

SGSN-1

BSC-1

RA-1

Old cell New cell

RA-2

• Moving between two RAs managed by same SGSN

• MS is moving and listening to broadcasts from cells

• MS selects new cell in another RA area but same SGSN


What is a periodic routing area update?• If an MS stays at the same place for a long time, the

network has to receive an indication that the MS is still reachable.

• This is the reason why the periodic routing area updates are made.

• All MSs attached to the GPRS will perform a periodic routing area update.


• 1 cell ≤ RA ≤ LA• Gs enables combined RA and LA updates• GPRS attach and RA update are always initiated by MS• Cell update takes place with any uplink packet• Both MS and SGSN may initiate GPRS detach (→ active PDP contexts deactivated)• Mobility management provides information to charging and statistics (→ M-CDRs)

LocationArea (LA)

RoutingArea (RA)

SGSN

MSC/VLR

GsI

Mobility management


What is session management?• Procedures that handle the GPRS MS connection to the

external data networks are called Session Management (SM).

• What types of SM procedures exist?• PDP Context Activation• PDP Context Deactivation• PDP Context Modification: modifying a PDP context

• What kinds of IP addresses can be used during a SM?• Static IP address (permanent MS IP address)• Dynamic IP address allocated by GGSN, DHCP, or

RADIUS server• HPLMN Dynamic IP Address

• VPLMN Dynamic IP Address


Steps during PDP context activation

• Receive request from subscriber• Check MS subscription data (static/dynamic, APN, etc.)• Authenticate subscriber• Check if IP address has to be allocated and by whom• Convert APN name to GGSN IP Address using DNS• Contact GGSN and check if it is prepared to accept MS• Await GGSN confirmation• Get ready for charging!!!

BTS BSC

SGSN

GGSNIntranet

GPRS Core

Network

DNS

Internet

AccessPoint


PDP context information

Mobile Station SGSN GGSN

PDP Type PDP Type PDP Type

PDP Address PDP Address PDP Address

NSAPI IMSI IMSI

APN NSAPI NSAPI

… APN APN

GGSN Address SGSN Address

Charging ID Charging ID

… …


SGSN

OperatorIP backbone

GGSNBorder Gateway

Inter operatorIP network Internet

Billing SystemCharging gateway

GPRS Charging Gateway:

• Receives CDRs generated bySGSN and GGSN

• Consolidates and merges CDRs to a suitable format for BS

GTP'

GTP'

Charging of GPRS services


Charging information from SGSN and GGSN


QoS


QoS classes Rel 97


Traffic classes Rel 99

Telephony

Videotelephony

Filedownloading

Webbrowsing

Maildownloading

Calendersynchronisation

Teleworking

Teleshopping

Streamingvideo

Streamingmusic

Own QoS-classesfor delay sensitive

services, packet losssensitive services

+ for combinations



+ for combinations

Conversational classStreaming class

Interactiv

e class

Backround class

TelephonyTelephony

VideotelephonyVideotelephony

Filedownloading

Filedownloading

Webbrowsing

Webbrowsing

Maildownloading

Maildownloading



TeleworkingTeleworking

TeleshoppingTeleshopping

Streamingvideo

Streamingvideo

Streamingmusic

Streamingmusic



+ for combinations



+ for combinations

Conversational class

Conversational classStreaming class

Streaming class

Interactiv

e class

Interactiv

e class

Backround class

Gprs 3 Traffic w

Documents

Transcript of Gprs 3 Traffic w