IMO a Contact is required in all provisional responses except for 100.
3261 definitely has the notion of early dialog which is established by
receipt of non-100 provisional response. (This would be an unreliable
provisional based on 3261, possibly reliable based on extensions.)
The early dialog of course cannot be established without a Contact. So
either the establishment of the early dialog is conditional on whether
the provisional has the Contact or not, or else the provisionals must
always have the contact. I don't recall any mention of this being
conditional, so I think the contact is always required.
Paul
Christer Holmberg (JO/LMF) wrote:
Hi,
At least in RELIABLE provisinal responses Contact is required, in order
to be able to send PRACK.
One of the issues we've been discussing before is whether an UAC is
allowed to send a non-CANCEL mid-dialog request once it has received an
UNRELIABLE provisional response. I think the conclusion has been that it
IS allowed, and in that case a Contact of course would be needed.
Whether we want to mandate Contact in unreliable provisional responses
or not is one issue, but as part of the new fix-the-bugs-in-3261 work
item it would give us an opportunity to clarify the issue.
Another, related, question which comes up every now and then: IF I
receive a provisonal response with a Contact, is it allowed to "update"
that Contact in the 200 OK (or, another reliable resonse)? Whatever the
answer is, I think some clarification text would be useful.
Regards,
Christer
-----Original Message-----
From: Jeroen van Bemmel [mailto:[EMAIL PROTECTED]
Sent: 26. toukokuuta 2007 13:52
To: [email protected]; [EMAIL PROTECTED]
Subject: Re: [Sip] Contact header in 1xx responses/updates
remote target ornot?
Dale,
Not sure if I read your comment right, but RFC3261 12.2.1.2 says
When a UAC receives a 2xx response to a target refresh request, it
MUST replace the dialog's remote target URI with the URI from the
Contact header field in that response, if present.
It does not say anything about 1xx responses here
though...Regards,Jeroen [EMAIL PROTECTED] wrote:
From: Nina Garaca <[EMAIL PROTECTED]>
Q1: Should I expect that these responses have a Contact header?
As Paul says, if it didn't have a Contact header, it couldn't
establish a dialog.
Q2: If they do so, should the remote target of the dialog be
refreshed by that Contact at the side that has received that 1xx
response and should the remote target of the dialog be
refreshed by
the Contact in the INVITE request at the side that has
received that
INVITE?
Responses are not "target refresh requests", so they don't
change the
target address at their end of the dialog. But of course, the
responses to the dialog-initiating request establish the initial
target address.
Q3: If not, should the remote target of the dialog be refreshed by
the Contact in the INVITE request
at the side that has received that INVITE and has sent dialog
establishing 1xx response?
RFC 3261 section 12.2:
INVITE, the only target refresh request defined is re-INVITE (see
Section 14). Other extensions may define different target refresh
requests for dialogs established in other ways.
Dale
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