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

[Brett Tate <[e-mail]>]

Hi,

The following are some comments concerning
draft-sparks-sipcore-refer-explicit-subscription-02.

Thanks,
Brett

-------

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.