Additionally if 18x contained SDP, you need to comply with offer/answer
rules when sending periodic 18x to comply with Timer C issues.  See
draft-ietf-sipping-sip-offeranswer for some clarification concerning
offer/answer rules.


> -----Original Message-----
> From: [EMAIL PROTECTED] 
> [mailto:[EMAIL PROTECTED] On 
> Behalf Of Paul Kyzivat
> Sent: Tuesday, May 20, 2008 10:11 AM
> To: Ganesh P
> Cc: [email protected]
> Subject: Re: [Sip-implementors] When need to send PRACK
> 
> As others have mentioned, the subsequent reliable 
> provisionals must increment RSeq. This flags them as distinct 
> responses, rather than retransmissions of the first response.
> 
>       Paul
> 
> Ganesh P wrote:
> > 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

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