Subject: RE: [Sipping] GRUU Issue: who did I call?

From: "Michael Procter" <[email-masked]>
Date: Mon, 31 Jan 2005 14:27:21 -0000

Cullen Jennings wrote:
> I read the whole thread and I think there is a very simple 
> solution....
> 
> The problem is that with the addition of GRUU  to SIP we have two
> addressable things - ones is a user (and addressed with AOR) 
> and other is device (addressed with GRUU)
> 

Yes.  There is another part of the problem though, which is where
we want to make a call to someone and all we have is the GRUU.

As Paul Kyzivat wrote earlier:
> >>> 
> >>> - Sending a new request to the old GRUU may well also not work.
> >>>   This negates the experimental approach to answering the "who did
> >>>   I call?" question, and also other usages, such as "I want to ask
> >>>   one more question of that guy Alice forwarded me to yesterday."

It seems to me that there are conflicting pressures on this.  Firstly,
Paul states that you should still be able to contact an entity for which
you only have a GRUU even after the GRUU expires.  Secondly, the GRUU
may be deliberately opaque to give some level of anonymity.

A simple solution that answers both questions seems to be for the
proxy/registrar responsible for the GRUU in question to optionally
respond to a request with a 3xx series response, rather than a 404.

This approach leaves the policy of GRUU->AOR mapping to the proxy/
registrar that manages the GRUU, thus allowing mapping to an AOR
to be performed if desired, or no mapping to preserve anonymity.

Won't this solve the problem without needing further drafts and
ammendments?

Regards,

Michael Procter

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---

From: Dean Willis <[email-masked]>
Date: Mon, 31 Jan 2005 11:08:37 -0600

> we want to make a call to someone and all we have is the GRUU.

One can't, by definition, always answer the question "Who does this 
GRUU belong to?", because that GRUU might no longer belong to someone. 
The AOR to GRUU binding is, to some extent, ephemeral, and by design is 
not required to be invertable.

The right question is: "Who did this GRUU correspond to at the time I 
used it?"

There are three possible answers:

1) Whoever gave me the GRUU wanted me to know, so they encoded their 
AOR into the GRUU.
2) When I used the GRUU earlier, I stored an associated AOR in case I 
wanted to be able to answer this question someday.
3) I dunno, and there's no way to find out easily, and thats a Good 
Thing.

--
Dean