Interesting,
That means that again that either Table-2 has made contact header
optional because section 12.1 + 12.1.1 is applicable for 101-199 ( not
100 trying ), but the table covers 100-199.
It would make sense to have contact header in 18x responses where
subsequent method have to be sent out ( except CANCEL method which
follows INVITE) as otherwise I was thinking how would the PRACK be
successfully delivered via stateless proxies absent contact header (
based purely on initial routing data available used for sending out
INVITE ).
So this implies that if a method has to be sent out after 18x ( like
PRACK/UPDATE etc ), then the 18x MUST have a contact header for
successfully routing those requests/methods through various proxies..
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 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.
Header field where proxy ACK BYE CAN INV OPT REG
___________________________________________________________
Contact 1xx - - - o - -
Contact 2xx - - - m o o
Table 2: Summary of header fields, A--O
Best Regards,
Indresh K Singh
>>-----Original Message-----
>>From: ext Brett Tate [mailto:[email protected]]
>>Sent: Tuesday, August 18, 2009 10:48 AM
>>To: Singh, Indresh (NSN - US/Boca Raton); ext raikkme rrrrr;
>>[email protected]
>>Subject: RE: [Sip-implementors] 18X response with no Contact Header
>>
>>> But as Vikram pointed out that contact header is an optional header
>>> in 1xx responses.
>>
>>The example indicates that the 18x with To tag (and without
>>Contact) was the dialog forming response. Thus the Contact
>>header is not optional.
>>
>>The following are two rfc3261 snippets which indicate that
>>the Contact is mandatory for such 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."
>>
>>
_______________________________________________
Sip-implementors mailing list
[email protected]
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
