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2.5.11 Use Multiple Endpoints


This use case, illustrated in the following diagram, describes how a user can sign in using multiple endpoints (5) and receive communications, such as an instant message or a VoIP call, initiated from another protocol client.


Figure 15: Steps for using multiple endpoints (5)



  • The protocol clients are signed in, as described in section 2.5.5.

  • User B is signed in with two protocol clients (Client B1 and Client B2).


  1. A user (Client A) initiates a session invitation request (SIP INVITE) to User B.

  2. The protocol server forks the session invitation (SIP INVITE) request to both of User B’s endpoints (5), Client B1 and Client B2, as described in [MS-SIPRE].

  3. User B’s protocol clients elect the most suitable endpoint (5) to accept the session invitation request on the user’s behalf. This process is facilitated by publishing capabilities through the presence channel, as described in [MS-PRES]. In this case, Client B1 accepts the session invitation request and sends a session accepted response (SIP 200 OK) to the protocol server.

  4. The protocol server cancels the session invitation request (SIP INVITE) that has been forked to the Client B2 endpoint (5), as described in [MS-SIPRE].

  5. The protocol server sends a session invitation accepted response (SIP 200 OK) to Client A.


  • Client A is now communicating with User B (Client B1).

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