Re: [sipcore] draft-sparks-sipcore-refer-explicit-subscription-02: comments

[Brett Tate <[e-mail]>]

Hi Robert,

Thanks for the response; reply is inline.

> > If something within this draft allows a RFC 6665 compliant notifier to
> > not supply a GRUU Contact within call's dialog, please clearly indicate
> > it.
> > For instance if true, indicate that the notifier is not required to
> > supply a GRUU Contact if notifier supports 'nosub' (even if referrer
> > does not support 'nosub').
> >
> > Section 6 indicates the following:
> >
> > "The 'explicitsub' and 'nosub' option tags MAY appear in the Supported
> >   header field of SIP messages, and in sip.extensions feature tag
> >   defined in [RFC3840].  This signals only that the UA including the
> >   value is aware of the extensions.  In particular, a UA can only
> >   invoke the use of one of the extensions in a request.  A User-Agent
> >   Server (UAS) that is processing a REFER request that lists
> >   'explicitsub' or 'nosub' in its Supported header field and wishes to
> >   use one of those extensions will return a 421 response indicating
> >   which extension is required.
> >
> >   OPEN ISSUE: This description of the use of 421 is not yet perfectly
> >   aligned with RFC3261's definition."
> >
> > I think that the open issue should be closed by not mandating the 421
> > response (at least if REFER was sent within dialog).  Similar to the
> > RFC
> > 3262 behavior, the UAS can indicate it is being used by including
> > option-tag within Require header of 2xx response.
> Hi Brett -
>
> I sent text last week proposing how to address this
> (Subject 'Open issue in refer-explicit-subscriptions').
> Was that text problematic for you?

The proposal continues to mandate that the option-tag only be honored if
received within a Require header of REFER.

If REFER is received within dialog, mandating that the UAS return a 421
appears to do nothing but require extra messaging for those attempting to
use it.  I recommend allowing behavior similar to RFC 3262 so that the
option tag can be within Supported of mid-dialog REFER and Require of
REFER's 2xx response.

Thanks,
Brett