Subject: Re: [Sip] Contact header in 200 OK

From: "Dale Worley" <[email-masked]>
Date: Wed, 30 Sep 2009 17:35:16 -0400

On Thu, 2009-08-06 at 20:15 +0530, sandip gangakhedkar wrote:
> I'd like to know if the Contact header is mandatory for a 200 OK
> response to an INVITE request. 

> If the originating endpoint receives the Contact header in the 180
> Ringing response (which I assume is mandatory), then it knows the
> location of the remote endpoint, in which case the Contact header
> would be redundant in the 200 OK response.

It would be redundant, but 1xx responses are (by default) not reliable,
so the UAS cannot depend on the UAC receiving the 180.

Dale