Subject: Re: [Sip] GRUU and Mid-Dialog Requests

From: "Xavier Marjou" <[email-masked]>
Date: Fri, 25 Aug 2006 11:07:20 +0200

I'm still not 100% convinced that extending the scope of the remote target 
(ie: Contact header field) to carry a gruu URI is necessary. 

What about the following alternative mechanism: 

- UA X obtains a GRUU AOR (eg: sip:ua-x;gruu=xyz) either by a response to a 
REGISTER request or by an external means.

- UA X must register his GRUU AOR before using it (as it recognize a gruu 
aor, the registrar only accepts one address-of-contact, so that forking 
towards multiple contacts is not possible)

- UA X can then use its GRUU AOR in its From header when sending an 
"initial" request, or substitute his AOR with its GRUU AOR in the To header 
when receiving an "initial" request. 

In this case, mid-dialog requests are not impacted. Moreover the anonymous 
property of the GRUU AOR may be left out of the GRUU spec, as it comes back 
to the general usage in From and To headers.

Xavier

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From: Paul Kyzivat <[email-masked]>
Date: Fri, 25 Aug 2006 09:00:09 -0400

> towards multiple contacts is not possible)

So you are defining the term "GRUU AOR" to mean an AOR that only accepts 
on registered contact.

> when receiving an "initial" request. 

That doesn't solve the use cases that GRUU was devised for.

The interesting cases are when UA X has registered at an AOR (lets call 
it AOR-X) that has multiple registered contacts. When UA X answers a 
dialog establishing request to AOR-X, it needs to put something in the 
Contact address - something that will route back to it.

I suppose, following your proposal, when it receives such a request it 
could but its gruu into the Contact of the response. But in that case we 
have all the same issues as the current proposal.

> to the general usage in From and To headers.

I think I must be missing something key in what you are proposing. It 
seems like you are simply suggesting that all problems go away if we 
never allow more than one contact to be registered with an AOR.

	Paul