Hi All,
I am new to this mail grpu and SIP world :). I need some information
about how to construct the CANCEL message at the proxy level.
Scenario
1> Caller A sends INVITE message to PROXY
2> PROXY(stateful) send 100 trying to caller A and sends the INVITE
message to caller B
3> Caller A sends CANCEL message to PROXY to cancel the INVITE message
4> PROXY send 200 OK and 487 response back to Caller A and checks for
1xx response from caller B and construct the CANCEL message to send to
caller B
5> PROXY construct this message with same Request-URI, TO , FROM,
CALL-ID and Cseq number field values of the INVITE message send to
caller B and insert it own VIA header field value. the branch id is
different from the one which is sent in INVITE message to caller B.
5> But the CALLER B sends 481 Call/Transaction Does Not Exist message
back to PROXY.
NOTE: if the CALLER B is CISCO media gateway, then it accept CANCEL
message by sending 200 OK and 487 message, But if it is a Pingtel phone
then it sends 481.
Any clue why the behavior is different here.
Thanks and Regards
-venkat
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