On 07/06/2010 02:04 AM, goutam kumar wrote:
> 1) If for an incoming call, the callee dosen't receive an ACK for a 200 OK,
> should the call fail??
Yes, by some notion of "fail," I suppose.
As someone new to SIP implementation, I recommend that you internalise
early on the importance of living and dying by unambiguous semantics.
What does it mean for a call to "fail" in this scenario? If the
specification itself were written in this equivocal language, no
interoperable real-world implementation would be possible.
See RFC 3261 13.3.1.4 "The INVITE is Accepted" in the general section
13.3 "UAS Processing":
If the server retransmits the 2xx response for 64*T1
seconds without receiving an ACK, the dialog is confirmed,
but the session SHOULD be terminated. This is accomplished
with a BYE, as described in Section 15.
> 2) In an outgoing call, if the end-user hangs-up a call, i.e. goes ON_HOOK
> while the remote party has still not answered the call, should the local SIP
> UA send a CANCEL message to the callee???
SIP has no notion of "ON_HOOK" -- is this some constant identifier in
the code you're working on?
To answer your question: yes. That is precisely the purpose of the
CANCEL request in the context of telephony signaling applications of
SIP. You seem to already know that this is the intended purpose of
CANCEL, so why do you ask whether the UAC _should_ send it? Would the
message exist if it were not intended to be used in the context
referenced in its definition? This is akin to asking if BYE should be
sent to terminate an established dialog.
--
Alex Balashov - Principal
Evariste Systems LLC
1170 Peachtree Street
12th Floor, Suite 1200
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