Subject: [Sip] Bis-7.9: Chapter 17.2.3

From: Christer Holmberg <[email-masked]>
Date: Thu, 21 Feb 2002 15:26:20 +0200

Hi,

A small issue on chapter 17.2.3 bis-7.9

Q1:

"The ACK request matches a transaction if the Request-
   URI, From tag, Call-ID, CSeq number (not the method), and top Via
   header field match those of the INVITE request which created the
   transaction,..."

Does the top Via match also in ACKs for transactions which created a 2xx
response? Aren't the branch-ids different in the INVITE and ACK?

"...and the To tag of the ACK matches the To tag of the
   response sent by the server transaction. Matching is done based on
   the matching rules defined for each of those header fields. The usage

   of the tag in the To header field helps disambiguate ACK for 2xx from

   ACK for other responses at a proxy, which may have forwarded both
   responses (which can occur in unusual conditions)."

Q2:

Should it be mentioned that ACKs for re-INVITEs will include a To tag,
even if a non-2xx responses is acked (I KNOW re-INVITEs aren't forked,
and that the To tag is not needed for the same purpose in that case).

Regards,

Christer Holmberg
Ericsson Finland

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---

From: Christer Holmberg <[email-masked]>
Date: Sat, 23 Feb 2002 01:37:48 +0200

Hi,

More on 17.2.3.

If an ACK is received for a 2xx response, the branch-id is not the only
parameter which will be different. To my understanding the Request-URI MAY
also be different, since the UAC will use possible Record-Route and Contact
headers in the 2xx response to create the ACK (the spec says that an ACK for
a 2xx response shall be created like any other transaction within the
dialog, so...)

Regards,

Christer Holmberg
Ericsson Finland