Re: [sipcore] draft-ietf-sipcore-rfc4244bis-callflows-02: "Reason"placement

OKUMURA Shinji <shinji.okumura@softfront.jp> Mon, 25 February 2013 10:03 UTC

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From: OKUMURA Shinji <shinji.okumura@softfront.jp>
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Cc: "Dale R. Worley" <worley@ariadne.com>
Subject: Re: [sipcore] draft-ietf-sipcore-rfc4244bis-callflows-02: "Reason"placement
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Hi, Dale.

worley@ariadne.com (Dale R. Worley)
Wed, 20 Feb 2013 15:49:44 -0500 (EST)
>In draft-ietf-sipcore-rfc4244bis-callflows-02, I find the following
>inconsistency.  Could people please advise me what the correct usage
>is?
>
>When a non-2xx final response is received by a proxy (or synthesized,
>in the case of timeouts), the response code is to be placed in the
>Reason header value in an hi-entry.  It turns out that there are two
>plausible choices:  One place is the hi-entry corresponding to the
>INVITE that was sent by the proxy and which matches the response
>received, the "next hop" location.  The other place is the hi-entry
>which is the address of the UA which generated the response, the
>"leaf" location.
>
>draft-ietf-sipcore-rfc4244bis-callflows-02 is not rich in failure
>responses, but there are these examples, with the corresponding
>hi-entries for the failed fork:
>
>   3.1.  Sequentially Forking (History-Info in Response)
>
>   History-Info: <sip:office@example.com>;index=1.2;mp=1
>   History-Info: <sip:office@192.0.2.5?Reason=SIP%3Bcause%3D408>;\
>                 index=1.2.1;index=1.2.1;rc=1.2
>
>   3.6.  PBX Voicemail Example
>
>   History-Info: <sip:carol@example.com>;index=1.2;mp=1
>   History-Info: <sip:carol@192.0.2.4?Reason=SIP%3Bcause%3D408>;\
>		      index=1.2.1;rc=1.2
>
>   3.7.  Consumer Voicemail Example
>
>   History-Info: <sip:carol@example.com?Reason=SIP%3Bcause%3D408>;\
>                      index=1.2;mp=1
>   History-Info: <sip:carol@192.0.2.4>;index=1.2.1;rc=1.2
>
>As you can see, these are inconsistent.
>
>My belief (which may be faulty) is that the "Reason" goes in hi-entry
>corresponding to the INVITE that the proxy sent, because that's what
>the proxy can easily determine.  Trying to find the right "leaf"
>hi-entry to attach the Reason to would be quite complicated in some
>forking cases.
>
>What is the right answer?

draft-ietf-sipcore-rfc4244bis-11
10.2.  Reason in the History-Info Header Field

   If the Reason header field is being added due to
   receipt of an explicit SIP response and the response contains any
   Reason header fields (see [RFC3326]), then the SIP entity MUST
   include the Reason header fields in the "headers" component of the
   hi-targeted-to-uri in the last hi-entry added to the cache, unless
   the hi-targeted-to-uri is a Tel-URI.  If the SIP response does not
   contain a Reason header field, the SIP entity MUST include a Reason
   header field, containing the SIP Response Code, in the "headers"
   component of the hi-targeted-to-uri in the last hi-entry added to the
   cache, unless the hi-targeted-to-uri is a Tel-URI.

according to this descriptions, SIP entity MUST include a Reason header
"in the last hi-entry added to the cache".
IIUC, it means "next hop" index=1.2.1.

Regards,
Shinji.