Thanks Gaurav, that's just what I needed. I can pretty much ignore the
unreliable one! Some work to do for 100rel but the basic mechanisms are
all there so that's not a big job.
Cheers
Steve

-----Original Message-----
From: Gaurav Kheterpal [mailto:[EMAIL PROTECTED] 
Sent: 05 July 2007 13:03
To: Stephen Paterson; [EMAIL PROTECTED]
Subject: RE: [Sip-implementors] INVITE with no SDP - provisional
response withSDP

In theory, any SIP message can include a session description in its
body.
But a session description in a SIP message is not necessarily an offer
or an answer.

Refer to Section 2.1.2 of draft-ietf-sipping-sip-offeranswer-01

Summarizing:-

When the INVITE request does not have an SDP,

* The first 1xx-rel MUST contain an SDP as the offer.
* The first 1xx (unreliable) MAY/MAY NOT include an SDP but it is not
the official offer (if included). It may be used as a preview for the
offer that'll subsequently follow.

I hope this helps.

Regards,
Gaurav

> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:sip- 
> [EMAIL PROTECTED] On Behalf Of Stephen 
> Paterson
> Sent: Thursday, July 05, 2007 5:14 PM
> To: [EMAIL PROTECTED]
> Subject: [Sip-implementors] INVITE with no SDP - provisional response 
> withSDP
> 
> Hi all,
> 
> Is it at all meaningful for an unreliable 1xx response to an INVITE to

> contain an SDP body when the INVITE itself did not? I'm aware of the 
> situation in the reliable case.
> I'm rather hoping that this is not allowed for the sake of making my 
> life easier but alas, I suspect it is. I certainly can't think of any 
> use for it as there is no means for the UAC to provide an answer 
> before it receives the final response. I also can't find anything in 
> the RFCs that mentions this situation in any way. If I've missed it, 
> please just point me to the relevant section of the RFCs. That should
be all I need.
> 
> Thanks
> 
> Steve
> 
> Steve Paterson
> Software Engineer
> Aculab
> Tel: +44 (0) 1908 273866
> Fax: +44 (0) 1908 273801
> Email: mailto:[EMAIL PROTECTED]
> Website: http://www.aculab.com
> 
> 
> 
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, 
> MK1 1PT, UK Registration No: 1397386 (Wales) P Please consider the 
> environment and don't print this e-mail unless you really need to 
> _______________________________________________
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, 
UK
Registration No: 1397386 (Wales)  
P Please consider the environment and don't print this e-mail unless you really 
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