Hi Paul, [I am adding Paul to this thread since he was a coauthor of RFC 3840]
please, see below the exchange between Brian and Kevin regarding draft-hanes-dispatch-fax-capability-06.txt. This was Brian's original comment: > Minor issue: > ------------ > > ... A UA > preferring the reception of fax calls MUST include the "sip.fax" > media feature tag in the Contact header field of REGISTER messages. > To confirm the registration of this preference, a SIP [RFC3261] > Registrar MUST then include this tag in the Contact header field of > its 200 OK response. > > If the Registrar does not do this (e.g. because it hasn't been updated > to support the new tag), what does the UA do when it receives the > 200 OK response that doesn't include the tag? Paul, can you share your views on this issue? Thanks, Gonzalo On 05/12/2012 6:02 PM, Brian E Carpenter wrote: > On 05/12/2012 14:12, Kevin Fleming wrote: >> I suppose it could choose to unregister and re-register in some other way >> in order to achieve its goals of receiving FAX calls, if it was configured >> with enough network information to do so. >> >> Now that I think about it some more, is a registrar even allowed to return >> a Contact header that differs from the one the UA supplied in its REGISTER >> request? I suspect this is *not* allowed, and so if the registrar supports >> Caller-Pref but the specific tag(s) in question fail some sort of >> validation process, its only recourse would be to fail the REGISTER request >> with a suitable error response. > > If that's the standard behaviour, it would of course answer my question. > > Brian > >> >> >> On Wed, Dec 5, 2012 at 6:35 AM, Brian E Carpenter < >> [email protected]> wrote: >> >>> On 05/12/2012 11:01, Kevin Fleming wrote: >>>> The language in RFC 3840 doesn't appear to contemplate the situation >>> you've >>>> proposed. In its world, registrars can either support prefs (and will >>>> accept "Require: pref") or they don't, and they don't have knowledge of >>>> which feature tags are registered with IANA and which are not. Of course, >>>> they *coud* attempt to validate the tags expressed by the UA, but I don't >>>> see an explicit way for the registrar to indicate that the UA included >>>> disallowed tags in its request. >>> Understood, but in that case I don't see what good the confirmation >>> of the tag from the registrar to the UA achieves - the UA is not going >>> to be able to do anything with it (except maybe log whether it was >>> received). >>> >>> Brian >>> >> _______________________________________________ Gen-art mailing list [email protected] https://www.ietf.org/mailman/listinfo/gen-art
