Registration Event Package Support

A registration is a binding between a SIP URI, or Address Of Record, and one or more contact URIs, which are additional resources to contact to reach the user identified by the Address Of Record.

The SBC supports UE subscribing to registration event package as defined in RFC 3680. This event defines a message-body in NOTIFY which carries UE contact details. SBC relays the message body appropriately. The SBC also performs V4-V6 interworking (if necessary) for SUBSCRIBE session setup.

If Contact header is transparently passed, there is no special handling needed at P-CSCF. Else, to support this package SBC intercepts and interprets NOTIFY’s message-body and changes the Contact header. This feature assumes that Contact header transparency is enabled along with it.

The SBC can receive SUBSCRIBE message (for registration event package) from a registered UE and relay the message based on stored Service-Route header and perform V6-V4 interworking if access side supports V6 and IMS CN supports V4 (i.e. stored Service-Route header points to V4). For this request, the SBC can:

• Act as a B2B UA and change the Contact header to point to itself towards the egress call-leg
• Optionally insert Record-Route header in the egress SIP request
• Relay 200 OK or any other final response towards UE, after interworking 200 OK’s Contact header appropriately

Similarly, SBC can receive NOTIFY (for registration event package) towards a registered UE and relay the message towards UE if the contact header transparency is enabled. Note that in the NOTIFY request, the UE IP address is received in Request-URI and the top-most Route header points to SBC.

When REGISTER is interworked from V6 to V4 or vice versa, or if the contact header transparency is disabled, the SBC changes the Contact header as it egresses the REGISTER request. The Contact address is changed to point to itself. Hence a NOTIFY is received for registration event package in such a scenario, SBC modifies the Contact header in NOTIFY message-body and send it towards UE.

• NOTIFY message body sent by S-CSCF contains all the contact headers registered for the public identity. The contact headers may also include the contacts registered by UE devices through different P-CSCF. The SBC modifies only the contact headers pointing to itself to UE IP address and leaves other contact headers unchanged.
• SBC modifies the contact address to all the contact address registered by UE if the multiple contact header registration (by single REGISTER) is supported by the SBC.

When the SBC acting as P-CSCF performs IP interworking, it receives NOTIFY (for registration event package) towards a registered UE and relay the same towards UE.

• In this case, the SBC interworks the IP address in NOTIFY’s message-body. The IP address in the message-body points to SBC. This changes to UE’s IP address before relaying NOTIFY towards the UE.
• In this case, if UE has registered multiple contact addresses then SBC interworks the IP address pointing to it to all the contact headers registered by UE.

The SBC also supports multiple contact address registrations by UE.

Example:

The following example enables regEventPackage on the core and peer IP signaling profiles.

% set profiles signaling ipSignalingProfile DFL_PCSCF_UE_TG_PROF commonIpAttributes relayFlags regEventPackage enable
% commit
% set profiles signaling ipSignalingProfile DFL_PCSCF_CORE_TG_PROF commonIpAttributes relayFlags regEventPackage enable
% commit

% show profiles signaling ipSignalingProfile DFL_PCSCF_UE_TG_PROF commonIpAttributes relayFlags regEventPackage
regEventPackage enable; 

% show profiles signaling ipSignalingProfile DFL_PCSCF_CORE_TG_PROF commonIpAttributes relayFlags regEventPackage
regEventPackage enable;