Hi,
The 180 Ringing is the provisional response. According to
RFC 3262,
Retransmission of 180 Ringing occurs till it receives PRACK.
In this scenario, PRACK is not received; the 200 OK response
of INVITE
is generated before receiving PRACK and is buffered.
As the 200 OK for INVITE is already sent. No further final
response can
be sent.
After certain retransmissions of 180 Ringing, CANCEL is sent
and 200 OK
for CANCEL is received.
How this INVITE transaction should be terminated.
How should SIP stack respond?
Also what happens when instead of CANCEL, BYE is sent?
Regards,
Madhuri
________________________________
From: Venkatesh [mailto:vvenkatar gmail.com]
Sent: Friday, May 26, 2006 11:34 AM
To: Nataraju A B
Cc: Madhuri Sakhare; sip-implementorscs.columbia.edu
Subject: Re: [Sip-implementors] Query Regarding Collision
case of
CANCEL.
Please check this thread. The CANCEL will get a 2xx
response.
https://lists.cs.columbia.edu/pipermail/
sip-implementors/2006-May/012974
.html
On 5/25/06, Nataraju A B <bnatarajukodiaknetworks.com>
wrote:
Thanks & Regards,
Nataraju A.B.
-----Original Message-----
From: sip-implementors-bouncescs.columbia.edu
[mailto:sip-implementors-bouncescs.columbia.edu] On Behalf
Of Madhuri
Sakhare
Sent: Thursday, May 25, 2006 7:40 PM
To: sip-implementorscs.columbia.edu
Subject: [Sip-implementors] Query Regarding Collision case
of CANCEL.
Hi,
Consider this call flow:
UAC UAS
| INVITE |
|----------------------->|
| 180 RINGING |
|<-----------------------|
| CANCEL |
|----------------------->|
| 200 OK CANCEL |
|<-----------------------|
| |
This is a collision case of a reliable 180 response and
a CANCEL
Request. The application on the callee side has sent a 200
OK response,
and the response is left pending in the SIP stack. Then the
collision
occurs and the CANCEL is indicated to the application, but
since it has
already sent a final response, it has no way of sending
another one. The
call is not freed.
How should the SIP stack responds to this?
[ABN] This scenario has been discussed in the list quite a
few times...
if the callee UA had already sent 200OK for INVITE then
200OK will not
be sent for CANCEL. CANCEL would be rejected with 481
responses...
The call will go through...
The caller's SIP stack has to initiate the BYE request to
terminate the
call once the INV/200/ACK transaction is completed... if the
user had
hung up the call...
Regards,
Madhuri
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