RE: Last Call: draft-lawrence-sipforum-user-agent-config (Session Initiation Protocol (SIP) User Agent Configuration) to Informational RFC

[Hadriel Kaplan <[e-mail]>]

> -----Original Message-----
> From: Scott Lawrence [mailto:[e-mail]]
> Sent: Thursday, April 08, 2010 9:37 AM
> To: Hadriel Kaplan
> 
> Well, one could argue that a provider could cause the returned SIP url
> for the change notice subscription to be one for which there is no
> routing (return 'Link: <sip:devnull.example.org>').  By the rules, the
> UA would periodically make a DNS request to try to find it, but would be
> allowed to use the configuration data.  Silly, but allowed.

Right, but the since that would make it an "unknown validity" config, and the requirements do not mandate any UA to *use* an "unknown validity" config... do you see a problem?

Instead of getting into an unknown-behavior state, why don't you simply allow the HTTP response to NOT have a Link header, or define a NULL URI to use - and then state that it means there is no Subscription service and the UA MUST consider the HTTP-based config valid?


> No one is going to be forced to use any of this specification.  If you
> don't want the features it provides (automatic initial configuration
> with prompt updates), then don't use it.

So we should go define another profile which is a textual copy of this one, but changes two sentences??  Is that really good for SIP or the SIP-Forum?

 
> At the risk of repeating myself, I want to make sure that one reason for
> using SUBSCRIBE/NOTIFY for the change notices is clear:  there is no
> other existing standard way to address a specific User Agent.  

Right, I understand that you have no other way to do X.  Fine, so specify how to do X.  Don't mandate that X be used with Y, when Y does not depend on X to function properly, and X is not trivial.

-hadriel