Confusion about ACK message failed in sip protocol

StackOverflow https://stackoverflow.com/questions/23311944

  •  10-07-2023
  •  | 
  •  

Question

According to sip protocol when first invite send, sip returns proxy authentication required message (if there are any proxy server available), then client send an acknowledge message. But what happen if the acknowledge message failed to reach the sip server? Server returns forbidden after sometimes and ignore all new invite with authentication header. Also when sip gets multiple acknowledge message it's immediately send forbidden. enter image description here

Was it helpful?

Solution

If your question is what would the correct behaviour be for a SIP server that has issued a 407 and not received an ACK for it, please see RFC 3261 17.2.1 for the description of the INVITE server transaction.

Sending the 407 moves the state machine into the "Completed" state, at which point the G and H timers have to be be set. When G fires, the 407 response needs to be retransmitted. And if all the ACK messages get lost, then timer H will make the server transaction give up eventually. But if the second ACK reaches the server then that's it. You will have seen two 407 responses, one with a lost ACK, the second one with a successful ACK.

The handling of the subsequent INVITE with the credentials should be entirely independent with the previously described process. The INVITE message with the credentials will constitute a separate dialogue forming transaction.

Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow
scroll top