Re: [dispatch] I-D Action: draft-hanes-dispatch-fax-capability-07.txt

I don't understand use case for this draft.  Unless I'm missing something, it helps to solve a very small corner case.

For the IP-UA to UA case, it seems very unlikely to be useful.  Of course someone _could_ construct a UA that sends T.38, but why bother when SMTP or mumble is so much less trouble.  So I don't see an actual problem here.

For the PSTN-UA to UA case, as the draft points out, there is no way to predict whether fax is going to be part of the call.  It's certainly true that increasing the probability of successfully handling a media stream, but I don't know how to figure out a priori how to set the balance between capabilities, convenience and whatever else the user's preferences are trying to tell us.

If the call is routed to BOB (Big Old Business), then I'd kind of expect that by administrative policy, the BOB administrators would set a routing policy if some of the incoming PSTN numbers were fax banks to route to fax capable UAs.  You _could_ solve the problem with preferences, but that seems like a lot of unnecessary nuance.  Routing policy is a hammer, for sure, but it's simple and works for this case.

If the call is routed to Bob Regular Guy, and assuming Alice can predict the preferences for that particular call (outside of any other preferences), then the draft solves an actual problem.

I think that the draft would be improved if the authors could add some words about how Alice would calculate a preference.

Cary.

On Jan 15, 2013, at 2:12 PM, internet-drafts@ietf.org wrote:

> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> 
> 
> 	Title           : Indicating Fax over IP Capability in the Session Initiation Protocol (SIP)
> 	Author(s)       : David Hanes
>                          Gonzalo Salgueiro
>                          Kevin P. Fleming
> 	Filename        : draft-hanes-dispatch-fax-capability-07.txt
> 	Pages           : 9
> 	Date            : 2013-01-15
> 
> Abstract:
>   This document defines and registers with IANA the new 'fax' media
>   feature tag for use with SIP.  Currently, fax calls are
>   indistinguishable from voice at call initiation.  Consequently, fax
>   calls can be routed to SIP user agents that are not fax capable.  A
>   'fax' media feature tag implemented in conjunction with caller
>   preferences allows for more accurate fax call routing.
> 
> 
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-hanes-dispatch-fax-capability
> 
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-hanes-dispatch-fax-capability-07
> 
> A diff from the previous version is available at:
> http://www.ietf.org/rfcdiff?url2=draft-hanes-dispatch-fax-capability-07
> 
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
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