[OpenSER-Devel] [Serdev] Possible bug in the tm module in the presence of packet loss/branches

[Juha Heinanen]

Dan Pascu writes:

 > Consider the case where the caller sends the CANCEL and the callee at the 
 > same time sends the 200 OK. They will intersect in the proxy, but when 
 > the callee receives the CANCEL it'll ignore it under the current RFC 
 > assumptions about the call setup, because once it has sent the 200 OK, it 
 > considers the session as started. Even if the caller ignores the 200 OK 
 > or use an ACK+BYE to end the session, the session is still
 > established. 

i don't see anything problematic in above, because the caller simply
canceled the call too late and caller phone should thus after receiving
200 ok, respond with ack and then terminate the call with bye.

you had some other example though that was not this simple.

 > But as you can see both need the cooperation of the UA. Otherwise we could 
 > apply 1 right now in the proxy, but it would most likely be completely 
 > ignored by all UAs out there.

ietf could go ahead specify a fix, but changing the protocol takes at
least three years and it won't help all the sip phones that are already
on the market.  also, this list is the wrong one to discuss changes in
UAs.

-- juha