Is it possible when 200OK for UPDATE request coming after 200OK for initial INVITE in SIP?

0
votes

I have a question about SIP, when read RFC [3311] UPDATE request, it doesn't mention that it's not invalid behavior in SIP. Here is the call flow:

  1. UAC sends INVITE request
  2. UAS sends 1xx INVITE to UAC
  3. UAC sends UPDATE request
  4. UAS send 2xx INV
  5. UAS send 2xx UPDATE

I supposes some reasons that made the 200OK for INVITE come first then 2xx response for UPDATE request coming after. Is this case a pass case in SIP call follow ?

Thank you guys.

1
sip

1 Answers

1
votes

Yes, that's perfectly OK.

This can happen when the UPDATE request and the 2xx INVITE response are sent 'simultaneously' and thus cross each other.

After the UAS has sent the 2xx INVITE response it will receive the UPDATE request and immediately send the 2xx UPDATE response. This means the session that was established due to the INVITE request/response will have a short lifespan since its session parameters will be updated according to the UPDATE session parameters.