Hi Eric,

The call flows document is in error - I will add the Contact in the 180 
response.  Thanks for pointing it out.

As for Table 2 in RFC 3261, the row you are referring to is for 1xx, which 
includes 100 Trying, in which a Contact is not mandatory, so I think the 
table is correct as it stands.

Thanks,
Alan Johnston
WorldCom
sip:[EMAIL PROTECTED]

At 05:12 PM 10/2/2002 -0400, Eric Cheung wrote:
>Hi
>
>I would like to seek clarification on whether UAS needs to put Contact
>header in 180 Ringing in response to an INVITE:
>
>In RFC3261 section 13.3.1.1:
>    ... provisional response between 101 and 199.  These provisional
>responses establish early dialogs and therefore follow the procedures of
>Section 12.1.1 in addition to those of Section 8.2.6.
>
>and section 12.1.1:
>    The UAS MUST add a Contact header field to the response.
>
>So it seems the UAS MUST put Contact header in 180 response.
>
>But in RFC3261 table 2, Contact is listed as optional.  Also in
>draft-ietf-sipping-call-flows-01.txt sec 3.1.1 F2 Contact header is
>absent.
>
>Where did I go wrong?
>
>Thanks
>Eric
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