Subject: RE: [Sip] INVITE without SDP body.

From: "Tom-PT Taylor" <[email-masked]>
Date: Fri, 1 Nov 2002 11:02:14 -0500

The problem is not with SDP, it's with the use of encapsulated protocol
content.  Without 100rel the UAS can't reliably deliver such content beforew
the final response.  This affects encapsulated ISUP too.
 
-----Original Message-----
From: Paraskevopoulos Pavlos [mailto:[email-masked]] 
Sent: Friday, November 01, 2002 9:31 AM
To: Christer Holmberg; [email-masked]
Subject: Re: [Sip] INVITE without SDP body.

Thanks for your response. 
I agree but I 'm a bit confused because in the 
draft-elwell-sippping-qsig2sip-03.txt (Interworking between SIP and QSIG),  
it is mentioned :

    If the SIP INVITE request does not contain SDP information and does not
contain
    either a Required header or a Supported header with option tag 100rel,
the gateway
    SHALL NOT issue a QSIG SETUP message and SHALL send a SIP 488 (NOT
ACCEPTABLE HERE) response.

What did I understand wrong?

Thanks again.

Christer Holmberg wrote:

Hi,

100rel is needed only if you want to use PRACK. It has nothing to do with
the
fact if you have a SDP in the INVITE or not.

Note, however, that if you use PRACK you may have to send the SDP before you
send the ACK (in a PRACK), but that's another issue...

Regards,

Christer Holmberg
Ericsson Finland

Paraskevopoulos Pavlos wrote:

  Hello,

I 'm trying to build a SIP gateway, and I would appreciate a little help.

Think of that scenario

ISDN                     GW                         SIP-EP
----------------------------------------------------------------
-->SETUP                 --->INVITE(no SDP)

             ALERTING<---                      180<-----
             CONNECT<---                       200<-----
                        ---->ACK(SDP)

I want to send the INVITE request without SDP info. The SDP info will
come later with the ACK.
Does the INVITE request have to contain a Required or Supported header
with option tag 100rel?

Thanks in advance.

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