Subject: [Sipping] From tag in CANCEL

From: Gonzalo Camarillo <[email-masked]>
Date: Wed, 15 Jan 2003 10:21:57 +0200

Alan,

in the service example draft,

http://www.ietf.org/internet-drafts/draft-ietf-sipping-service-examples-03.txt

Some CANCELs have a tag in the From header field and some don't. For
example, the CANCEL (F6) in page 73 does not have a tag, but the CANCEL
(F9) in page 135 has it.

Quoting from RFC 3261 (section 9.1):
" The
   Request-URI, Call-ID, To, the numeric part of CSeq, and From header
   fields in the CANCEL request MUST be identical to those in the
   request being cancelled, including tags."

Therefore, even if a CANCEL is generated by a proxy, it will have to
have the From tag.

The behavior regarding From tags for ACKs for non-2xx final responses
generated by proxies is the same (Section 17.1.1.3).

Regards,

Gonzalo
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---

From: Alan Johnston <[email-masked]>
Date: Wed, 15 Jan 2003 15:07:06 -0600

Gonzalo,

Thanks for the comments.  Agreed - I will make the corrections on CANCEL 
tags.  I also plan to go over the Call Flows I-Ds one last time to make 
sure that the tag usage is correct there.

Thanks,
Alan.