Re: [Sip] Error reporting in caller prefs

["Adam Roach" <adam@dynamicsoft.com>]

"Jonathan Rosenberg" <jdrosen@dynamicsoft.com> writes:
> I am inclined to go with approach 3, adding the appropriate discussions 
> on the privacy considerations. The specific algorithm I would propose is 
> this. If the caller prefs selection process results in zero contact, the 
> proxy re-runs the algorithms without the implicit preferences. If now, 
> there are contacts remaining, it concludes that the implicit preferences 
> caused the problem. It then checks to see if the problem was methods or 
> event packages, and generates a 405 or 489 accordingly.

Two comments; one con, one "interesting":

1. It seems to me that this approach adds a substantial burden
   to the proxy.

2. This has the interesting effect of forcing the proxy to
   aggregate the methods and the event-packages
   available for an address-of-record. (e.g. if I have
   a client registered that supports MESSAGE,
   and one that supports INVITE, the proxy-generated
   405 will ostensibly indicate both INVITE and MESSAGE
   as acceptable methods.) Of course, this may well exacerbate
   the security problems you discuss -- but it also might
   be a useful feature. It also has the odd consequence that
   I can get a more accurate picture of your capabilities
   by intentionally sending an invalid method than
   I can by sending an OPTIONS...

/a

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