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sip
Niraj73
Niraj73

Reputation: 53

Possible scenario for receiving SIP 487 Request Terminated message

What are all the possible scenarios for an originating system to receive a 487 (Request Terminated) message from the destination end in response to an Invite message, before receiving 18X messages from the destination, and without any CANCEL message sent by the originator after sending the INVITE message?

Upvotes: 2

Views: 5757

Answers (1)

Zaboj Campula
Zaboj Campula

Reputation: 3360

The 487 Request terminated is created only as reaction to the CANCEL request. Nevertheless the CANCEL may be generated by a stateful proxy. See the RFC-3261 chapter 16.10. A stateful proxy may generate the CANCEL due to timer expiration for example.

The CANCEL request must not be sent before a provisional response is received. But the provisional response do not need to be a 18x response. UAC or proxy may send CANCEL even after 100 Trying is received. And moreover it is sufficient that the proxy receives a provisional response.

So there is the answer: There are almost infinite number of all possible scenarios because there are plenty of SIP proxy implementations and their configurations and they may have a lot of reasons to cancel a transaction.

Upvotes: 3

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