Re: scope of derive

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of
> Scott Lawrence
> Sent: Friday, December 05, 2008 6:16 PM
>
> A From Address will often fail to reach the caller if used as a request
> target.
>

Right - this was the same issue people had with Dan's return-routability test.

>         It is by no means assured that a SUBSCRIBE request will be
>         routed to the same set of UAs that an INVITE would be.  In
>         particular, a SUBSCRIBE coming from outside the callers domain
>         may often be subject to policy based routing or rejected without
>         ever reaching the UA of even a legitimate caller.

Correct - this was noted in an earlier email on this topic a few weeks ago as well.
It's actually worse than that, BTW.  We've already noted that the UAC would in fact have to support the dialog-event package; as would every b2bua in the middle that changed a call-id, and you'd have to hit all those same b2bua's.
These all reduce the probability of a positive check result. (for some of us fairly drastically)


> Even in
> that case, it would indicate an unverified caller so often that the
> callee would be unwise to make any firm judgment based on it, so the
> callee is in exactly the position they are in today - the From address
> is a hint.

Exactly - that was my point about the Palin/Sarkozy problem not really being resolved.

-hadriel
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