Diameter Maintenance and Extensions Working Group Requirement of Session State Machine for Diameter Server Initiated Session Tina TSOU (ITU-T Q. 5/11 Rapporteur) Sudhir MITTAL

2 Background Q proposes to use DIAMETER on Rw Interface. The Rw interface exists between Policy Decision Physical Entity (PD-PE) and the Policy Enforcement Physical Entity (PE-PE) where PD-PE acts as the diameter server and the PE-PE acts as the diameter client. Two modes of operation are defined on this interface –PULL : PE-PE (Diameter Client) establishes session with PD-PE (Diameter Server). State Machine for this mode is defined in Diameter Base RFC(3588). –PUSH : PD-PE (Diameter Server) establishes session with PE-PE (Diameter Client). State Machine for this mode is not defined in Diameter Base RFC(3588).

3 Why Both Push and Pull? Service Control Session signalling e.g. SIP+SDP Policy Decision Point Policy Enforcement Point User Data Possible user resource control signalling e.g. RSVP Rs interface uses Q (Diameter) Rw interface uses Q.3303.x (Diameter, etc.) PEP duties: packet admission/rejection QoS marking of packets NAT For sessions without user resource control signalling, Rs interface is used for authorization, reservation, and commitment (PUSH mode, triggered by session signalling). For sessions with user resource control signalling, request for commitment flows from PEP to PDP across the Rw interface (PULL mode).

4 DIAMETER Works For PULL Session Initiating event CCR (new session id, initial request) CCA (session id, policy) Modifying event CCR (session id, update request,...) CCA (session id, policy) Clearing event CCR (session id, termination request,...) PEP Diameter Client PDP Diameter Server CCA (session id,...)

5... But Not For PUSH PEP Diameter Client PDP Diameter Server Session Initiating event ?

6 What ITU-T Authors Propose PEP Diameter Client PDP Diameter Server Session Initiating event Session Initiation Request (new session id) Session Initiation Response (session id)

7 discussions Victor Fajardo 2/08/2007 –PD-PE to initiate client session towards PE-PE Sudhir Mittal 2/10/2007 –PE-PE,acting as client, initiates client session towards PD-PE in PULL Mode –PD-PE already acting as server in PULL initiates session towards PE-PE in PUSH Mode Victor Fajardo 2/11/2007 –PD-PE being server doesn’t necessarily mean that it should act as Diameter Server. Therefore it can use Diameter Client State Machine Sudhir Mittal 2/12/2007 –PD-PE acting as server or client is not an issue –PD-PE needs to interact with PE-PE using Diameter protocol –This interaction(session) is initiated by PD-PE in PUSH and PE-PE in PULL –Therefore PD-PE is acting as Diameter Client for Push and hence it can't send RAR following Client State Machine but the same node is acting as Diameter Server in PULL. –Thus PD-PE shall act,dynamically, as Diameter Server and Diameter Client which shall lead to a complex specification. Victor Fajardo 2/12/2007 –Addition of server initiated session creation message shall lead to change in fundamental behaviour of server as defined in Tolga Asveren 2/13/2007 – PD-PE could implement,separately, client and server state machine.The kind of message received shall decide which state machine is used. –Or,PD-PE could implement a single state machine containing both server and client entries.

8 discussions..contd. Sun Dong 2/13/2007 –Existing state machine can work with the addition of two new commands through which server can initiate session –PD-PE implementing a single state machine containing both server and client entries will be complex. Victor Fajardo 2/13/2007 –Modular approach could be followed by separately implementing client and server state machine in PD-PE Rajith R 2/13/2007 –Agrees with Sun Dong,but suggest handling server initiated session message in client state machine Rajith R 2/14/2007 –If PD-PE takes policy decision, it needs to send RAR but this is not provisioned in client State Machine Victor Fajardo 2/14/2007 –Several Application running successfully using existing State machine –Changing the expected behavior to accommodate PD-PE may not be appropriate Sudhir Mittal 2/15/2007 –If PD-PE acts as diameter client for PUSH mode then it will not send RAR and ASR. Therefore some new messages may be added for providing functionality of ASR and RAR Victor Fajardo 2/15/2007 – PD-PE can use STR in place of ASR and if RAR is being used in PULL then it is available in PUSH also.

9 Proposed LS reply to ITU-T extend the stateful client & server state machines (in RFC 3588) for authorization considering the ITU-T LS. For server: StateEventActionNew State IdleIndication to push auth. information to the client. Send service specific auth. request Pending Service specific auth. request received. Send failure service specific auth. response Pending Successful service specific auth. response received. NoneOpen PendingFailure service specific auth. response received CleanupIdle PendingProcessing error in successful answer Send ASRDiscon

10 Proposed LS reply to ITU-T (Cont’) For client: StateEventActionNew State IdleIndication to push auth. information to the client. Send service specific auth. request Service specific auth. request received & processed successfully IdleService specific auth. request received. Send failure service specific auth. response Service specific auth. request received & processing failure PendingSuccessful service specific auth. response received. NoneService specific auth. request received & processed successfully PendingFailure service specific auth. response received CleanupService specific auth. request received & processing failure these are in addition to the transitions already defined by the RFC.