session management

WS03/04, TKN TU Berlin, Stefan Lehnert Course UMTS Networks, Cornelia Kappler

UMTS

Session Management

WS03/04, TKN TU Berlin, Stefan Lehnert Session Management, UMTS Networks Page 1

Introduction• Session Management (SM) establishes, modifies

and releases packet data sessions with well defined QoS between UE and GGSN

• Packet session attributes are called PDP contexts• A UE may have more than one PDP context

simultaneously, each with a SM protocol entity

UE SGSN GGSNSM protocol GTP-C protocol

Entities involved


PDP Context Contents• PDP = Packet Data Protocol (generic name)• protocols to be used: IP (likely), X.25

U E k e e p s S G S N k e e p s G G S N k e e p s

M o b ility M a n a g e m e n t in fo

p lu s :

M o b ility M a n a g e m e n t in fo

p lu s :

IM S I, M S IS D N p lu s

P D P ty p e (P P P , IP )

P D P a d d re s s ( IP a d d re s s )

P D P s ta te

P D P ty p e

P D P a d d re s s

P D P s ta te

P D P co n te x t id e n t if ie r

P D P ty p e

P D P a d d re s s

d y n a m ic a d d re s s a llo w e d d y n a m ic a d d re s s u s e d

A P N re q u e s te d A P N in u s e

N S A P I & T I N S A P I & T I N S A P I

Q o S re q u e s te d , n e g o t ia te d Q o S su b s c r ib e d , re q u e s te d ,

n e g o t ia te d

Q o S n e g o t ia te d

C h a rg in g in fo rm a tio n C h a rg in g in fo rm a tio n

T E ID (T u n n e l E n d p o in t ID ) T E ID (T u n n e l E n d p o in t ID )


Session Management Procedures• SM procedures require existing GMM context• SM procedures are:

– PDP context activation• PDP address, QoS etc. are set• UE must be in PMM-CONNECTED state

– PDP context modification• QoS etc. is modified• UE must be in

PMM-CONNECTED state

– PDP context deactivation• packet data session is released• PDP context also deactivated when UE moves to PMM-IDLE or

PMM-DETACHED state

PMMDETACHED

PMMIDLE

Reminder: PMM state model

PMMCONNECTED


Session Management State Model (1)

PDPACTIVE

PDPINACTIVE

Activate PDP contextDeactivate PDP context

orMM state change to

PMM-IDLE orPMM-DETACHED


Session Management State Model (2)

PDPACTIVE

PDPINACTIVE

PDP-ACTIVEPENDING

PDP-INACTIVEPENDING

PDP-MODIFYPENDING

DI(Deact. PDP REQ)

DI(Act. PDP ACC)

DI(Deact. PDP REQ)

DI(Deact. PDP ACC)DI(Act. PDP REQ)

DI(Mod. PDP REQ)

DI(Act. PDP REJ)

DI(Mod. PDP ACC)

DI(Mod. PDP REJ)

DR(Deact. PDP REQ)

DR(Mod. PDP ACC)

DR(Deact. PDP REQ)

DR(Deact. PDP ACC)

DR(Deact. PDP ACC)

DR(Act. PDP REQ)

DR(Act. PDP REQ)

DR(Mod. PDP REQ)

DI = Data Indication (Message received by UE); DR = Data Request (Message sent by UE)

still incomplete ...


8. Deactivate PDP Context Request

7. Activate PDP Context Accept6. Update PDP Context Response

5. Update PDP Context Request

4. Radio Access Bearer Setup3.b Create PDP Context Response

2.b Create PDP Context Request3.a Activate PDP Context Reject

2.a Activate PDP Context Reject

1. Activate PDP Context Request

PDP Context Activation by UE

• Request (1) contains NSAPI, PDP type, QoS, PDP address (static, dyn.)• Reject may occur due to insufficient ressources, unknown PDP address

or PDP type, unsupported or not subscribed options wished• Request (8) may occur if network does not offer requested QoS

UE RAN SGSN GGSN


3.b Failure

5.b Failure

1. PDP PDU

7. PDP Context Activation procedure

6. Request PDP Context Activation

2. Send Routing Info for GPRS

3. Send Routing Info for GPRS ACK

PDP Context Activation by network

• If HLR cannot determine a SGSN or the SGSN cannot find the UE with specified IMSI, the PDP Context Activation Procedure fails (3.b, 5.b)

• After the SGSN‘s request the UE performs the PDP Context Activation

UE SGSN HLR GGSN

4. PDU (Packet Data Unit) Notification Request

5. PDU Notification Response



5. Update PDP Context Response

2.b Update PDP Context Reject

4.b Deactivate PDP Context Request

3. Modify PDP Context Request

4. Radio Access Bearer Setup



4. Modify PDP Context Accept

PDP Context Modification by network

• GGSN (below blue line) or SGSN (above line, without blue messages) can initiate the network PDP context modification procedure

• If UE does not accept the PDP context modification request, it shall initiate the PDP context deactivation procedure instead

UE RAN SGSN GGSN


5.b Deactivate PDP Context Request

3.b Update PDP Context Reject

4.b Modify PDP Context Reject

1. Modify PDP Context Request

4. Radio Access Bearer Setup



5. Modify PDP Context Accept

PDP Context Modification by UE

• If the network does not accept the PDP context modification request, the UE may initiate the PDP context deactivation procedure instead of keeping the previous PDP context

UE RAN SGSN GGSN


1. Deactivate PDP Context Request

5. Radio Access Bearer Release

3. Delete PDP Context Response

2. Delete PDP Context Request

4. Deactivate PDP Context Accept

PDP Context Deactivation by UE

• The UE request contains the Transaction Identifier (TI) - so the SGSN knows which PDP context is to be torn down

• If the UE includes the tear down indicator, all PDP contexts of the current PDP address will be deactivated

UE RAN SGSN GGSN



1. Delete PDP Context Request3. Deactivate PDP Context Request

6. Radio Access Bearer Release


1. Delete PDP Context Request

4. Deactivate PDP Context Accept

PDP Context Deactivation by network

• GGSN (below blue line) or SGSN (above line, without blue messages) can initiate the network PDP context deactivation procedure

• The message sent to the UE contains the Transaction Identifier (TI) -so the UE knows which PDP context is being deactivated

UE RAN SGSN GGSN

session management

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