Re: [sipcore] Verify draft-ietf-sipcore-rfc4244bis-callflows-02.txt

[[e-mail] (Dale R. Worley)]

The History-Info shown in example 3.6 F6 (of the -02 version) is:

  History-Info: <sip:[e-mail]>;index=1
  History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
                     index=1.1;rc=1
  History-Info: <sip:[e-mail]>;index=1.2;mp=1
  History-Info: <sip:carol@192.0.2.4?Reason=SIP%3Bcause%3D480>;\
                     index=1.2.1;rc=1.2
  History-Info: <sip:[e-mail];\
                     target=sip:bob%40example.com>;\
                     index=1.3;mp=1
  History-Info: <sip:vm@192.0.2.6;\
                     target=sip:bob%40example.com>;\
                     index=1.3.1;rc=1.3

In regard to this example Marianne Mohali has written (and I have
heavily abridged):

> From: <[e-mail]>

> [MM2] No, there is no mistake in the code, the correction were done
> after one of my comments. Here we are in a Call Deflection immediate
> response situation (as defined in TS24.604) and the cause URI
> parameter value to be used and defined in RFC4458 is 480. My point
> was about the format which is a [Reason header's cause parameter]
> format instead of the [cause URI parameter] format in the URI.
> 
> The line should be:
> History-Info: <sip:carol@192.0.2.4;cause=480>;\
>  		 index=1.2.1;rc=1.2 
> 
> >From RFC4458
>                 +---------------------------------+-------+
>                 | Redirecting Reason              | Value |
>                 +---------------------------------+-------+
>                 | Unknown/Not available           | 404   |
>                 | User busy                       | 486   |
>                 | No reply                        | 408   |
>                 | Unconditional                   | 302   |
>                 | Deflection during alerting      | 487   |
>                 | Deflection immediate response   | 480   |
>                 | Mobile subscriber not reachable | 503   |
>                 +---------------------------------+-------+

> [MM2] OK, so the following hi-entry (index=1.3.1) must contain a
> cause URI parameter set to "cause=408" (removed from the draft-01
> version)

As I understand them, the suggestions are:

    The target sip:[e-mail] (index 1.2) is generated from
    sip:[e-mail] by "deflection immediate response", and so that
    URI should be augmented with the parameter cause=480.  I assume that
    parameter is carried into the hi-entry 1.2.1.

(It is not clear to me whether RFC 4458 applies exactly here, since
the deflection is not directly to voicemail but rather to Carol.
However, it seems that the intention of RFC 4458 is to describe how to
mark deflections to targets other than VM as well.  Probably
comparison with PSTN operation is the way to resolve this question.)

    The target sip:[e-mail] (index 1.3) is generated from
    sip:[e-mail] due to timeout of the INVITE to
    sip:carol@192.0.2.4 (index 1.2.1).  So hi-entry 1.2.1 gets
    "?Reason=SIP%3Bcause%3D408" and hi-entry 1.3 gets a URI parameter
    ";cause=408".  I assume that parameter is carried into the hi-entry
    1.3.1.

If I haven't made any mistakes, the marked changes need to be made:

  History-Info: <sip:[e-mail]>;index=1
  History-Info: <sip:bob@192.0.2.5?Reason=SIP%3Bcause%3D302>;\
                     index=1.1;rc=1
  History-Info: <sip:[e-mail];cause=480>;index=1.2;mp=1
                                      ^^^^^^^^^^
  History-Info: <sip:carol@192.0.2.4;cause=480?Reason=SIP%3Bcause%3D408>;\
                                    ^^^^^^^^^^                      ^^^
                     index=1.2.1;rc=1.2
  History-Info: <sip:[e-mail];\
                     target=sip:bob%40example.com;\
                                                 ^^
 		     cause=408>;\
                     ^^^^^^^^^
                     index=1.3;mp=1
  History-Info: <sip:vm@192.0.2.6;\
                     target=sip:bob%40example.com;\
                                                 ^^
 		     cause=408>;\
                     ^^^^^^^^^
                     index=1.3.1;rc=1.3

These changes need to be made to these hi-entries wherever they appear
in the example, except the "Reason=SIP%3Bcause%3D408" for 1.2.1 only
appears in F6 and F7.

Also, in F3, the Contact header becomes:

  Contact: <sip:[e-mail];cause=480>;mp=1

Additionally, the last paragraph of the description of 3.6 seems to
have a damaged sentence:

   Furthermore it is the proxy forwarding the call to VMS that
   determines the target of the voicemail, it is the proxy that sets the
   target of voicemail which is also the entity that utilizes RFC4244bis
   to find the target which is usually based on local policy installed
   by the user or an administrator.

It might be helpful to add this note at F4:

  F4 INVITE Example.com -> Carol

  Because the call was forwarded from Bob to Carol due to "deflection
  immediate response", the URI parameter "cause=480" was added to
  Carol's AOR per [RFC448].  That parameter was carried through to
  Carol's contact URI during internal retargeting.

  INVITE sip:carol@192.0.2.4 SIP/2.0
  ...

Dale