16 Jun
2008
16 Jun
'08
8:50 p.m.
Nuno Ribeiro wrote:
I would like your opinion about a scenario, i.e. if the SER is having the
correct behavior in our scenario. The scenario is the following one:
We have a basic scenario where a SIP proxy sends an INVITE and afterwards a
CANCEL message to another SIP proxy. The last SIP Proxy answers with a 513
Message too big to the CANCEL message. When the first proxy receives this
answer message it will discard it and won't forward it back to the client
that tried to establish a call. In attachment I send you the wireshark
capture.
CANCELs are hop-by-hop, meaning that proxies process the CANCEL instead
of forwarding it. While the process it and if necessary, they create a
new CANCEL for the request they sent on earlier.
You can see that in your trace. When the proxy (10.112.64.80, port 5060)
receives the CANCEL in message 12, it creates a 200 OK for it and sends
it back in message 14 and also creates a new CANCEL in message 13 which
it sends on. When it then receives the 513 in message 14, the first
CANCEL has already been answered and it can't do a thing.
HTH and regards,
Martin