IMS AKA Notification Message Flows

AKA Notification services include:

Subscription to Registration state events

IMS AKA Subscription to REG events

Figure F-30: Message flow for Subscription to Register events (UDP or TCP).

The following list shows simplified the procedures for Subscription to Registration state events in the figure above.

  1. The UE builds a SIP Subscribe request message requesting notifications about Registration events.

  2. The SIP Subscribe request message is sent to the P-CSCF’s protected server port.

  3. The SIP Subscribe request message is passed to the home S-CSCF, where the request is processed.
    A SIP 200 OK response message is returned to the UE.

  4. The SIP 200 OK response message is sent to the UE’s protected client port if the TCP protocol is used.

  5. The SIP 200 OK response message is sent to the UE’s protected server port if the UDP protocol is used.

  6. The subscription is registered by the UE.

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Notification of Registration state events

IMS AKA Notification of REG events
Figure F-31: Message flow for Notification of Register events (UDP or TCP).

The following list explains simplified the procedures for Notification of Register events in the figure above.

  1. The S-CSCF builds a SIP Notify request message with the Registration event.

  2. The SIP Notify request message is sent to the UE’s protected server port.

  3. The SIP Notify request message is received and processed by the UE.
    A SIP 200 OK response message is returned to the S-CSCF.

  4. The SIP 200 OK response message is sent to the P-CSCF’s protected client port if the TCP protocol is used.

  5. The SIP 200 OK response message is sent to the P-CSCF’s protected server port if the UDP protocol is used.

Other actions may follow by the UE such as a Re-Registration request.

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