2011/7/27 Brett Tate <[email protected]>:
> The following are two rfc3261 snippets which indicate that the Contact is
> mandatory for dialog creating 18x responses.
>
> Section 12.1: "Dialogs are created through the generation of non-failure
> responses to requests with specific methods. Within this specification, only
> 2xx and 101-199 responses with a To tag, where the request was INVITE, will
> establish a dialog."
>
> Section 12.1.1: "When a UAS responds to a request with a response that
> establishes a dialog (such as a 2xx to INVITE)" ... "The UAS MUST add a
> Contact header field to the response."
And table 2 in page 162 says:
Header field where proxy ACK BYE CAN INV OPT REG
___________________________________________________________
Contact R o - - m o o
Contact 1xx - - - o - -
Contact 2xx - - - m o o
So it says that Contact header is optional (o) in 1XX responses for an INVITE.
However I agree with you, section 12 clearly says that a 1XX response
(which I do know that creates an early-dialog) MUST mirror
Record-Route and contain Contact header. However Table 2 above does
not say it. Strange.
Anyhow this topic is a source of discussions. IMHO it's bad specified
in the RFC. I remember from other discussions more issues like the
presence of Record-Route and Contact in a 1XX or 2XX response
different than those in a previous 1XX. There are ugly rules for that
specified somewhere in the RFC.
Regards.
--
Iñaki Baz Castillo
<[email protected]>
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