Hi,

Some nodes don't support INVITE without SDP, even if it's allowed in the standard.

If you send an INVITE without SDP, there is no way to say "I want a vocal session". Of 
course, when you receive an offer in 200 OK you can accept/reject the media types and 
payloads you want, and indicate that in your answer sent in the ACK.

Regards,

Christer Holmberg
Ericsson Finland




-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED]
Sent: 17. maaliskuuta 2004 14:06
To: [EMAIL PROTECTED]
Subject: [Sip-implementors] INVITE without SDP


Hello,

draft-ietf-sipping-3pcc-06.txt refers to INVITE messages sent without SDP body so as 
to manage third party call control.
But how a such INVITE must be formated (which headers...) so as to invoke called party 
to send generate the offer in its 200 response, and to be shure the offerd session 
will be a vocal session (for example).
I tried to send INVITE (See above message) request to a free Sip phone, but it 
responds with a status error to my request. and does not sends back any offer.

Message sent:
INVITE sip:[EMAIL PROTECTED] SIP/2.0
Via: SIP/2.0/UDP 172.17.119.1;maddr=172.17.119.1;branch=z9hG4bK3f31158-2155
Max-Forwards: 70
Supported: 100rel
From: <sip:[EMAIL PROTECTED]>;tag=161546080
To: <sip:[EMAIL PROTECTED]>
Call-ID: [EMAIL PROTECTED]
CSeq: 1 INVITE
Contact: <sip:[EMAIL PROTECTED];maddr=172.17.119.1>
Content-Length: 0

Message received:
SIP/2.0 500 Internal server error (cannot align media streams)
Content-Length: 0
Contact: <sip:172.17.2.183:5060>
Call-ID: [EMAIL PROTECTED]
CSeq: 1 INVITE
From: <sip:[EMAIL PROTECTED]>;tag=161546080
To: "0476617954"<sip:[EMAIL PROTECTED]>;tag=8143920
Via: SIP/2.0/UDP 172.17.119.1:5060;maddr=172.17.119.1;branch=z9hG4bK3f31158-2155

Thank you for your help.

C�dric.

-- 
C�dric BARRET
IN & GSM Infrastructure Department 
FERMA, ZIRST, 31 Chemin du Vieux Chene 
38240 MEYLAN, FRANCE 

Tel : +33 (0)4.76.61.79.00 
Fax : +33 (0)4.76.61.79.59 
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