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3.9.5.2.2 Rules for Handling the INVITE

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The SIP proxy authorized for the address-of-record in the Request-URI field SHOULD perform the following steps in order when handling the INVITE request:

  1. If the block flag is set, the proxy SHOULD reject the request with a 480 Temporarily Unavailable response, and further processing of rules SHOULD be stopped.

  2. If the e911active flag is set, the proxy SHOULD route the call only to registered endpoints. The registered endpoints timer SHOULD NOT be started and further processing of rules SHOULD be stopped.<49>

  3. If the INVITE is an audio app-invite and the forward_audio_app_invites flag is not set, the proxy SHOULD route the call only to registered endpoints. The registered endpoints timer SHOULD NOT be started and further processing of rules SHOULD be stopped.<50>

  4. If the INVITE is targeted at the private line of the user, the call SHOULD be processed as specified in section 3.9.5.2.2.4.

  5. If the INVITE was routed to the user as a result of team or delegate ringing processing for some other user, the proxy SHOULD route the call only to registered endpoints and the registered endpoints timer SHOULD NOT be started. Further processing of rules SHOULD be stopped.<51>

  6. If the address-of-record in the URI of the From or Referred-By header fields, as defined in [RFC3892] section 3, is present in the breakthrough list, the call SHOULD be routed to the primary targets as specified in section 3.9.5.2.2.1, and further processing of rules SHOULD be stopped.<52>

  7. If the work_hours flag is set and the current time is outside the working hours in the calendarData publication, as specified in [MS-PRES] section 2.2.2.7.8, the call MUST be forked to the registered endpoints whose address-of-record matches the address-of-record in the Request-URI field, except that do-not-disturb presence state MUST be handled as specified in step 10.

  8. If the team_ring flag is set, team ringing SHOULD be processed as specified in section 3.9.5.2.2.3 and further processing of rules SHOULD be stopped<53>

  9. If the delegate_ring flag is set, delegate ringing SHOULD be processed as specified in section 3.9.5.2.2.2 and further processing of rules SHOULD be stopped.<54>

  10. If the user's presence  published in the state  for the container to which the caller belongs, as described in [MS-PRES], is "do-not-disturb", the call MUST be routed to the target user's voice mail and further processing of rules SHOULD be stopped. If the call cannot be routed to voice mail because of Ms-Sensitivity header field value considerations described in section 3.9.5.2.1, a response indicating failure SHOULD be returned.

  11. If none of the preceding conditions apply, the call MUST be routed to primary targets as specified in section 3.9.5.2.2.1.