2.5.9 Initiate Instant Messaging

Office

This use case, illustrated in the following diagram, describes how a user sends an instant message to another user.

Steps for initiating instant messaging

Figure 8: Steps for initiating instant messaging

References

Preconditions

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

Steps

  1. Client A sends a session initiation message (SIP INVITE) with the target address of Client B to the protocol server by using the Session Initiation Protocol (SIP) Routing Extensions, as described in [MS-SIPRE].

  2. The protocol server routes the session invitation to Client B by using the Session Initiation Protocol (SIP) Routing Extensions, as described in [MS-SIPRE].

  3. Client B sends a session accepted response (SIP 200 OK) to the protocol server to accept the session.

  4. The protocol server routes the session accepted response (SIP 200 OK) to Client A. The session is now established. The client A sends an acknowledgment (ACK) request in response to the 200 OK. Please note in the interest of brevity this step is not explicitly called out in the diagram above.

  5. Client A sends the conversation text (SIP MESSAGE) and target address of Client B to the protocol server by using the Session Initiation Protocol (SIP) Routing Extensions, as described in [MS-SIPRE].

  6. The protocol server routes the session conversation text to Client B by using the Session Initiation Protocol (SIP) Routing Extensions, as described in [MS-SIPRE].

  7. Client B sends a message received response (SIP 200 OK) to the protocol server.

  8. The protocol server routes the message received response (SIP 200 OK) to Client A.

Post-conditions

  • The instant messaging (IM) conversation between Client A and Client B is in progress.

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