In this case, it's a re-invite and the iTSP does not support the Invite
without SDP.

The ITSP in this case is Broadvox.   They have two platforms, their "Legacy"
and their "Fusion" platforms.   sipXecs is fully compatible with their
Legacy platform, but is not compatible with their Fusion since they require
SDP within the Re-Invite.

SO, if you are going to use Broadvox, ensure they provision your system for
the legacy platform only.  It works great.

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Jean-Hugues Royer
Sent: Sunday, September 26, 2010 4:09 PM
To: [email protected]
Subject: Re: [sipx-dev] ITSP handling of Invites without SDP

Hi Todd,

INVITEs without SDP are perfectly legit, they are usually used by the 
inviter to get the full list of supported codecs of the phone.

Because on a regular INVITE with SDP some phones select/provide only one 
of the codec in the response SDP and the inviter is not aware of all the 
other supported codecs.

In the case of INVITEs without SDP, the phone usually gives all its 
supported codecs in the response SDP, and the inviter selects/provides 
its codec(s) in the SDP of the ACK sent after receiving the response.

It's some kind of inverted offer/answer if you prefer.

Regards.

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