gprs traffic management_1

1 © NOKIA 6-64453 v.4 / 25.10.2004

GPRS Traffic ManagementGPRS Traffic Management

2 © NOKIA 6-64453 v.4 / 25.10.2004

Objectives

At the end of the module the participant will be able 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 IP addressing in GPRS

• Describe charging in GPRS

• Explain the concept of security in GPRS

• Describe the data flows for a roaming GPRS MS

without using any references.

3 © NOKIA 6-64453 v.4 / 25.10.2004

Traffic Management: Subscriber’s and Operator’s Point of View

content

content

Networkserver

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content

content

Networkserver

http

TCP

http

TCP

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content

content

Networkserver

http

TCP

http

TCP

IP IPIP IP IP IPRelay Relay

Router Router

ISP 1 (e.g. LAN) ISP 2 (e.g. WAN) ISP 2 (e.g. LAN)

6 © NOKIA 6-64453 v.4 / 25.10.2004


content

content

Networkserver

http

TCP

http

TCP

IP IPIP IP IP IPRelay Relay

Router Router

GPRS network infrastructure ISP 2 (e.g. WAN) ISP 2 (e.g. LAN)

GGSNMS

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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

GMM

GMM

GPRS MSSGSN

HLR

8 © NOKIA 6-64453 v.4 / 25.10.2004

What is traffic management?

Traffic management procedures are subdivided into two areas:

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, PDP context modification

corp.network

WAP

PDNSession Management

GPRS MSSGSN

HLR

GGSN

active PDP contextdata flow

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Identities: Analogy between GSM & GPRS

• CGI (Cell Global Identity)• LAI (Location Area Identity)

at VLR• VLR-no at HLR

GSM

• IMSI (International MobileSubscriber Identity)

• TMSI (Temporary MobileSubscriber Identity)

• dialled MSISDN (MS ISDN no)

• CGI (Cell Global Identity)• RAI (Routing Area Identity)

at SGSN• SGSN-no at HLR

GPRS

• IMSI (International MobileSubscriber Identity)

• P- TMSI (Packet Temporary Mobile Subscriber Identity)

• APN (Access Point Name)• QoS (Quality of Service)• PDP (Packet Data Protocol)

e.g. IP or X.25

Where is the subscriber?

Who is the subscriber?

What does the subscriber want?

10 © NOKIA 6-64453 v.4 / 25.10.2004

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

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Regional Organisation of GPRS

MCCMobile Country

Code

MNCMobile Network

Code

LACLocation Area

Code

CICell

Identity

RACRouteingArea Code

LAILocal Area Identifier

CGICell Global

Identity

RAIRouting

Area Identifier=

=

LA

RA

CI

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GMM States: Summary

IDLE(no valid MM context)SGSN: • ???MS:• not reachable• PLMN selection• cell selection

READYSGSN:• RA and CIMS:• receive/transmit PDPs• PLMN selection• cell selection & update• (de-)activation of

PDP contextsHLR: SGSN-no

STANDBYlogical link between

MS and SGSNSGSN: • RA• PtP pagingMS:• cell selection• RA Update• (de-)activation of

PDP contextsHLR: SGSN-no

GPRS Attach

READY timer expired,

Force to STANDBY,abnormal RLC condition

STANDBY timer expired,Cancel Location

PDU transmissionGPRS DetachCancel Location (SGSN only),

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MS states

RA-1

VLR-1

HLR

SGSN-1BSC

LA-1

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MS Idle

RA-1

VLR-1

HLR

SGSN-1BSC

IMSI 244...VLRSGSN

IMSILAISGSN ?

IMSI ?RA ?Cell ?

LA-1

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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 cell-1cell-1

LA-1

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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

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GPRS Attach (no PLMN change)MS

newSGSN

oldSGSN

Attach Request

HLRMSC/ VLR

Identification Request

Identification Response

Security: authentication & optional equipment check

Location Update

Cancel Location & Ack.

Insert Subscriber DataUpdate Location Ack.

Location Updating Request

Location Updating Accept

normal LU

Attach Accept

Attach CompleteTMSI Reallocation Complete

Securityfunctions

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GMM procedure “GPRS attach” (0)

RA-1

HLR

SGSN-1

BSC

LA-1

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GMM procedure “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.

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GMM procedure “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 send it to SGSN.

(3g) SGSN verifies (SRES=SRES’).

RA-1

HLR/AC

SGSN-1

BSC

LA-1

3a

3b

3f

3c

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IMEI check

RA-1

EIR

SGSN-1

BSC

LA-1

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).

4a

4b

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RA-1

HLR

SGSN-1

BSC

LA-1

5a

5b

5c

5d(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.

6a

6b

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Location Management: Analogy between GSM & GPRS

Location AreaUpdate Procedures

in MM state: INACTIVE

• normal location update(MS in a new location area, mandatory)

• Periodic location update(timer set after last interactionto see whether mobile is stillavailable, optional)

• IMSI attach/detach(a flag is set when MS is switched off, optional)

GSM GPRS

Routing Area Update Procedures

in GMM state: READY & STANDBY

• normal routing area update(MS in a new routing area, mandatory)

• Periodic routing area update(timer set after last interactionto see whether mobile is stillavailable, optional)

• IMSI attach/detach(a flag is set when MS is switched off, optional)

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Location Management: Analogy between GSM & GPRS

Handover

in the MM state: ACTIVE (DEDICATED)

There are only• network initiated handovers

• time critical: (real-time)

Cell selection and update

in the GMM state: READY

There are• MS initiated cell updates• network initiated cell updates

(if supported by manufacturer)

• Non-time critical: (non-real time)

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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

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SGSN

BSC

LA-1

GGSN

1

New RA

Intra-SGSN RA update (1)

(1) MS requests from SGSN an update of MM context by sending ‘Routing Area Update Request.’

30 © NOKIA 6-64453 v.4 / 25.10.2004

SGSN

BSC

LA-1

GGSN

2b

22a

New RA

Intra-SGSN RA update (2) (2) SGSN authenticates MS and sends RAND as a challenge.(2b) SIM calculates SRES and sends it to SGSN as a response. (2c) SGSN allocates new P-TMSI and new ciphering Key Kc.

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GGSNSGSN

BSC

LA-1

4

23

New RA

Intra-SGSN RA update (3 & 4)

(3) SGSN checks that MS is allowed to attach to RA, and then sends RA Update Accept message with new P-TMSI.

(4) If P-TMSI reallocated, MS acks new P-TMSI with a ‘Routing Area Update Complete’ message.

32 © NOKIA 6-64453 v.4 / 25.10.2004

Inter-SGSN routing area update

SGSN-1

BSC-1

RA-2

Old cell New cell

RA-3

SGSN-2

BSC-2

• MS moves between two RAs managed by different SGSN

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Inter-SGSN routing area update (1 & 2 )

Old SGSN

New SGSN

RA-1

BSC

LA-1

2b

GGSN

2a

1

1. MS sends a RA Update Request to the new SGSN.

2a. The new SGSN sends SGSN Context Request to the old SGSN.

2b. The old SGSN responds with SGSN Context Response.

34 © NOKIA 6-64453 v.4 / 25.10.2004

Inter-SGSN RA update (3) authentication

GbaseNew SGSN

RA-1

BSC

LA-1

Old SGSN

GGSN

3d

2

3a

3b

3c

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SGSN and MSC/VLR interaction

LA 1

LA 2

RA 11

RA 12

RA 12

RA 21 RA 21

MS classA or B

I have to

indicate a new

LA and RA

NSS

SGSN

MSC/VLR

location update

for GPR

S

location update

for GSM

Overheadon

radiointerface

39 © NOKIA 6-64453 v.4 / 25.10.2004

SGSN and MSC/VLR interaction

LA 1

LA 2

RA 11

RA 12

RA 12

RA 21 RA 21

MS classA or B

I have to

indicate a new

LA and RA

NSS

SGSN

MSC/VLR

Gs

Combined

location update

LA updateinternally

SAVINGS:

• Combined GPRS/IMSI attach and detach

• Combined RA/LA update

• Circuit switched services paging via GPRS network

• Non-GPRS alerts

• Identification procedure

• MM information procedure

40 © NOKIA 6-64453 v.4 / 25.10.2004

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 contextcorp.

network

WAP

PDNSession Management

GPRS MSSGSN

HLR

GGSN

active PDP contextdata flow

41 © NOKIA 6-64453 v.4 / 25.10.2004

PDP Context Activation

MS SGSN GGSN

1. Activate PDPContext Request

- PDP Address (empty = dynamic)- PDP Type (e.g. IPv4 or IPv6)- Access Point Name (APN)- PDP Configuration Options

DNSServer

2. SecurityFunctions

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MS SGSN GGSN


DNSServer

DNSinquiry

SGSN gets the GGSN IP address from DNS, which maps APN to the GGSN IP address.


43 © NOKIA 6-64453 v.4 / 25.10.2004


MS SGSN GGSN


DNSServer

DNSinquiry

3. Create PDPContext Request

- PDP Address (empty = dynamic)- PDP Type (e.g. IPv4 or IPv6)- Access Point Name (APN)- Proposed TID- QoS & other options


44 © NOKIA 6-64453 v.4 / 25.10.2004


MS SGSN GGSN


DNSServer

DNSinquiry


4. Create PDPContext Response

-PDP address- TID - charging identifier- QoS negotiated- PDP configuration options

Connection establishment

with PDN


45 © NOKIA 6-64453 v.4 / 25.10.2004


MS SGSN GGSN


DNSServer

DNSinquiry




with PDN

5. Activate PDPContext Accept

- PDP address- TID - Radio priority options- QoS negotiated- PDP configuration options


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MS SGSN GGSN



DNSServer

DNSinquiry




with PDN

5. Activate PDPContext Accept

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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

… …

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Roaming: Two Options

BSS NSS

visited PLMN

SGSN

GGSN PDN 1IP BB

BG

BSS NSS

home PLMN

SGSN

GGSNIP BB

BG

PDN 2

inter PLMNnetwork

IP address dynamicand

APN specified or non-specified

IP address: staticor

IP address dynamic &APN specified

49 © NOKIA 6-64453 v.4 / 25.10.2004

Non-Transparent Access to external PDN

MS SGSN




4. Create PDPContext Response5. Activate PDP

Context Accept

externalPDN

RadiusServer

GGSN

RadiusClient

DHCPServer

AccessRequestAccessAccept

DHCPClient

DiscoveryOffer (IP address, etc.)

Ack. (IP address, etc.)Request (IP address, etc.)


with PDN

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Non-Transparent Access to external PDN

Result:

External PDN

RouterGPRS networkinfrastructureincl. SGSN,

GGSN, IP BB

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Transparent Access to Mobile Operator‘s PDN

MS SGSN




4. Create PDPContext Response5. Activate PDP

Context Accept

externalPDN

GGSN

RadiusClient

AccessRequestAccessAccept

IP addressfrom

internalIP

Addresspool


with PDN

RadiusServer

52 © NOKIA 6-64453 v.4 / 25.10.2004

Result:

Mobile operator‘s GPRS network

GGSNTunnel

incl. SGSN,IP BB

Transparent Access to Mobile Operator‘s PDN

external PDN

external PDN

external PDN

53 © NOKIA 6-64453 v.4 / 25.10.2004

MSC

G-MSC

SGSN

HLR

SMSC

1)

2)

3a)

3b)

4a)

4b)

a) MSC addressb) SGSN address

SMS data transfer1. SMSC forwards the SM to an SMS-GMSC , which examines

destination MS address.2. GMSC request info from HLR which returns MS's current SGSN

&| MSC number.3a. If result contains an MSC number then the SMS-GMSC forwards the SM to

MSC.4a. The MSC then transfers the SM to the MS.3b. If result contains SGSN number, the SMS-GMSC forwards the SM to the

SGSN.4b. The SGSN then transfers the SM to the MS.

54 © NOKIA 6-64453 v.4 / 25.10.2004

SGSN

OperatorIP backbone

GGSNBorder Gateway

Inter operatorIP network Internet

Billing SystemCharging gateway

Nokia GPRS Charging Gateway:

• Receives CDRs generated by SGSN and GGSN• Consolidates and merges CDRs to a suitable format for BS

GTP'

GTP'

Charging of GPRS services

55 © NOKIA 6-64453 v.4 / 25.10.2004

GGSN charging functions

CG

Internet

GGSN

OperatorIP backbone

SGSN

G-CDRs

GGSN CDR (PDP context data): G-CDR

Start collection:- PDP context activation

Stop collection:- PDP context deactivation

Collected information, e.g.- Traffic volumes uplink/downlink- QoS negotiated- Duration- SGSN & GGSN address- Access point name

56 © NOKIA 6-64453 v.4 / 25.10.2004

SGSN charging functions

SGSN CDR (PDP context data): S-CDRStart collection:

- PDP context activationStop collection:

- PDP context deactivationCollected information, e.g.

- Traffic volumes uplink/downlink- QoS requested/negotiated- Duration- SGSN & GGSN address- Access point name

Mobility Management CDR: M-CDRStart collection:

- GPRS activation / Incoming SGSN RA update

Stop collection:- GPRS deactivation / Outgoing SGSN RA update

Collected information - Location changes

CG

S-CDRsM-CDRsSMS-CDRs

Internet

GGSN

OperatorIP backbone

SGSN

58 © NOKIA 6-64453 v.4 / 25.10.2004

Security

MS Authentication

userinformation

Confidentiality(ciphering)

user identityConfidentiality

(TMSI)

accesscontrol

(screening)

GPRS security features

additional security features

Ciphered linksand authentication

between GPRSnodes

Hidden IP addressingin IP BB

Firewalls

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Lawful Interception GatewaySGSN

GGSN

LIG LEA

InternetX.25

Normal data transfer

Intercepted data transfer

Gn

National interface

62 © NOKIA 6-64453 v.4 / 25.10.2004

Traffic classes

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

Interacti

ve 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

Interacti

ve class

Interacti

ve class

Backround class

63 © NOKIA 6-64453 v.4 / 25.10.2004

Review Questions toReview Questions to„GPRS Traffic Management“„GPRS Traffic Management“

64 © NOKIA 6-64453 v.4 / 25.10.2004

1. Where is the mobility management context established?

2. In each state, Idle, Ready and Standby, which location information does the system have?

a) In the MSCb) In the SGSNc) In the GGSN

a) Idle:

b) Ready:

c) Standby:

Review

Network has no information about the MS

HLR: SGSN-noSGSN: CGI (cell information) and RAI (routing area)

HLR: SGSN-noSGSN: RAI (routing area) only

65 © NOKIA 6-64453 v.4 / 25.10.2004

3. In which states does the network not have to page the MS?

4. After GPRS attach, with the mobile in Ready state, is it possible to send and receive packets?

a) Idle and Readyb) Ready and Standbyc) Standby and Idle

Review

Not before activating a PDP context. With this PDP context an IP address is assigned to the mobile.

66 © NOKIA 6-64453 v.4 / 25.10.2004

5. Who can initiate the GPRS Detach?

6. Which new area is defined in GPRS compared to GSM?

7. How are the routing areas distributed between the SGSNs and location areas?

a) The MS onlyb) The SGSN onlyc) Both the MS and the SGSN

The RAI, Routing Area Identity. RAI= MCC+MNC+LAC+RAC

Review

A routing area is always served by just one SGSN. An SGSN can control several routing areas. A routing area is a subset of a location area. A location area can have several routing areas.

67 © NOKIA 6-64453 v.4 / 25.10.2004

8. What kind of 'updates' do we have in GPRS?

9. Which two kinds of IP addresses are there in GPRS?

a) Cell update: Mobile in READY state changes from one cell to another

b) Routing area update: Mobile changes from one routing area to another. (Intra SGSN and Inter SGSN, normal and periodic update)

Review

Static IP address: The IP address is assigned to the mobile permanently (the same in every PDP activation).

Dynamic IP address: A different IP address is assigned to every PDP context activation.

68 © NOKIA 6-64453 v.4 / 25.10.2004

10. Which confirms or provides the tunnel ID, IP address, and charging ID?

11. What kind of benefits can an operator acquire from an SGSN and MSC/VLR interface?

a) SGSNb) GGSNc) DNS

Review

Efficient usage of radio resources through combined RA/LA update, combined IMSI/GPRS attach/detach, etc. Note: class A or B MSs are required

69 © NOKIA 6-64453 v.4 / 25.10.2004

12. State two modes that are used for a subscriber to access an external data network.

13. How does a visited SGSN find its home network?

Transparent and non-transparent. The former is a GPRS operator acting as the ISP. The latter is the external ISP or intranet allocated IP address for the subscriber.

Review

From the access point name (APN) raised by the subscriber or the subscriber‘s application.

The APN identifies a (set of) GGSNs, which offer a connection to the external PDN the subscriber wants to get connected to. Normally, a DNS server in the VPLMN is used for name resolution.

70 © NOKIA 6-64453 v.4 / 25.10.2004

14. In which cases will the visiting user select or be forced to use the home GGSN and visited GGSN?

Case 1: Selecting the visited GGSN could be faster to connect to a public Internet site, but probably more expensive.

Case 2: Selecting the home GGSN could be the only way to connect to a corporation's network (like Intranet), or a cheaper way to connect to the public Internet.

Review

A subscriber can be restricted by the HLR to use the home GGSN:

Case 1: The user has a permanent IP address allocated by the home GGSN.

Case 2: The home operator would like to control its subscribers.

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15. What are the additional GPRS security features?

16. Define the meanings of LEA and LIG

a) Private IP addressing in the GPRS backbone b) Ciphered links and authentication between

nodes in the GPRS backbone, as well as between network operators

c) Firewalls

Review

LEA- Legal Enforcement Agency. Provides information about a certain pre-defined target subscriber. This information could be sent or received data, location information, etc.

LIG – Legal Interception Gateway. Collects the GPRS data and converts it to the Legal Enforcement Agency format.

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17. How many routes could an SMSC-GMSC choose to deliver a SMS?

18. Which network elements are responsible for collecting CDRs? Which one provides interface to Customer Care and Billing System?

It can route in the "classic" way toward the MSC or choose the "GPRS" way and use the SGSN. Requires Class A or B MS.

Review

SGSN and GGSN are responsible for collecting CDRs. These CDRs are transferred to the Charging Gateway (CG) and then forwarded to the CCBS.

gprs traffic management_1

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