Subject: [Sip] concerns on draft-elwell-sip-tispan-connected-identity-01

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 07 Jul 2006 15:49:42 -0400

I wasn't able to find any disucssion on this draft so far in the 
archives; my apologies if I missed it.

This draft concerns me greatly.

The first thing that worries me is the general idea that 3gpp or tispan 
get to 'choose' which SIP header field contains what type of identity. 
They get to do no such thing. These header fields have defined meanings. 
Having either organization decide to specify their own interpretation 
for the type of identity that goes in there is a guarnateed receipe for 
huge, massive, and unending interoperability failures.

On the technical front, I strongly disagree that the From and 
P-Asserted-Identity represent different types of identity in any way. 
They both have always identified the user that is the sender of the 
request. In cases where you had an enterprise user Joe making a SIP 
call, the From would contain sip:[email-masked] and this would be 
authenticated by the proxy in the enterprise, followed by insertion of a 
P-Asserted-ID which says the same thing. The From, in this use case, 
should not be sip:enterprise.com.

Next, I am puzzled by the requirement to deliver separate identities to 
the calling party for these two things. I understand the concept of a 
billing identity being separate from the identity of the caller. I do 
not, however, understand why the billing ID is of any interest to the 
called party whatsoever. It seems that this would, at best, be of 
interest only within the domain of the calling party. Since its also 
directly inferrable from the identity of the caller (presumably the 
database contains a linkage between the two), I also don't see why it 
would need to be carried in the sip message itself. Is there a use case 
where there is not a provisioned relationship between the user making 
the call and the billing entity? Certainly there is a clear direct 
relationship in the enterprise example in the draft.

Finally, even if I buy the idea that there are two identities and that 
they both need to be conveyed, I strongly disagree with the notion that 
one of them can be conveyed with SIP-identity, while P-A-ID is OK for 
the other. There are certain well-known technical limitations with 
P-A-ID which sip-identity addresses. There is nothing about the nature 
of the identity which invalidates any of those issues.

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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