Hi Ganesh,
UAS can send additional reliable provisional response provided
the prior sent reliable provisional responses have been acknowledged.
And every new reliable provisional response sent should have RSeq number
incremented exactly by 1.
Check this statement in RFC 3262
After the first reliable provisional response for a request has been
acknowledged, the UAS MAY send additional reliable provisional
responses. The UAS MUST NOT send a second reliable provisional
response until the first is acknowledged. After the first, it is
RECOMMENDED that the UAS not send an additional reliable provisional
response until the previous is acknowledged. The first reliable
provisional response receives special treatment because it conveys
the initial sequence number. If additional reliable provisional
responses were sent before the first was acknowledged, the UAS could
not be certain these were received in order.
The value of the RSeq in each subsequent reliable provisional
response for the same request MUST be greater by exactly one. RSeq
numbers MUST NOT wrap around.
Paul, Vikram and Arun, let me know your thoughts on this.
Thanks,
Bharat
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
Ganesh P
Sent: Tuesday, May 20, 2008 6:48 PM
To: 'Paul Kyzivat'; [EMAIL PROTECTED]; [EMAIL PROTECTED]
Cc: [email protected]
Subject: Re: [Sip-implementors] When need to send PRACK
Hi Paul/Arun/Vikram,
If it should not retransmit for extending the transaction what
it
should do. Whether it should again construct one more provisional
response
assume it is sending 183 session progress reliably for the second time
in 2
minute 30 seconds again if it wants to go ahead with extending the
transaction which header it should change (we cannot increment the cseq
number). I have copied some RFC sentences below please check
"The CSeq number is incremented for each new request within a
dialog
and is a traditional sequence number. (it is not for responses)"
" the UAS needs to send them more frequently (once a minute is
recommended) because of the possibility of packet loss. As a more
efficient alternative, the UAS can send the response reliably, in
which case the UAS SHOULD send provisional responses once every two
and a half minutes. Use of reliable provisional responses for
extending transactions is RECOMMENDED."
Thanks and Regards,
Ganesh
-----Original Message-----
From: Paul Kyzivat [mailto:[EMAIL PROTECTED]
Sent: Tuesday, May 20, 2008 5:45 PM
To: Ganesh Pitchiah S
Cc: [email protected]
Subject: Re: [Sip-implementors] When need to send PRACK
Clarification question:
Is the second 180 truly a retransmission, or is it a *new* 180?
Paul
Ganesh Pitchiah S wrote:
> Hi All,
>
> I have a doubt regarding continuous transmitting of provisional
> response. In our system we are having two SIP entities
>
> Assume one sip entity is softx and other is SCP.
>
> SCP sends 180 with SDP to softx to have early dialog and we are having
a
> situation that early dialog should go for 4 minutes.
>
> After 2 minutes and 30 seconds SCP is retransmitting the 180 with SDP
again
> but the softx is not accepting the same because it has already send
PRACK
> for the earlier response and it is releasing the call after 3 minutes
> because it did not get any new response.
>
>
>
> Can any one say whose behavior is correct? (I checked with RFC3262 I
think
> SCP behavior is correct)
>
>
>
> Thanks in advance.
>
>
>
> Thanks and Regards,
>
> Ganesh
>
>
>
>
>
> _______________________________________________
> Sip-implementors mailing list
> [email protected]
> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>
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