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----- Original Message ----- 
From: "Stephen Paterson" <[EMAIL PROTECTED]>


> Hi all,
>
> What happens if the 1xx does not contain a contact header? According to
> RFC 3261, this is optional for 1xx response (see table 2, page 162), it
> is only mandatory for 2xx response. Does 3262 update this at all? I
> can't find anywhere in it that does.

The text of the specification must be considered in addition to the values 
in the table. For example, a 100 Trying response would not contain a 
Contact, but 180 Ringing should.

According to RFC 3261, if the UAS is generating a response that is 
establishing a dialog, then it MUST add a Contact. A 101-199 response (that 
includes a To tag) to an initial INVITE (i.e. request does not have a To 
tag) is a response that establishes a dialog (based on section 12.1).

12.1.1 UAS behavior

   When a UAS responds to a request with a response that establishes a
   dialog (such as a 2xx to INVITE), the UAS MUST copy all Record-Route
   header field values from the request into the response (including the
   URIs, URI parameters, and any Record-Route header field parameters,
   whether they are known or unknown to the UAS) and MUST maintain the
   order of those values.  The UAS MUST add a Contact header field to
   the response.  The Contact header field contains an address where the
   UAS would like to be contacted for subsequent requests in the dialog
   (which includes the ACK for a 2xx response in the case of an INVITE).

However, I have run into rare cases where the UAS does not comply with RFC 
3261 and a Contact is not present. In this case, the we use the route set 
from the Record-Route headers, but the Request-URI is the same as the 
original INVITE.

cheers,
(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
71 Third Avenue
Burlington, MA 01803
[EMAIL PROTECTED]


>
> Cheers
>
> Steve
>

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