Subject: [Sip] Comments on draft-rosenberg-sip-identity-coexistence

From: "Elwell, John" <[email-masked]>
Date: Thu, 09 Nov 2006 01:52:48 +0000

Jonathan,

Apologies if these comments have already been made.

Section 1 "When the request arrives at the terminating UA, it first checks
for the Identity and Identity-Info header fields. If present, the identity
in the From header field is used as the caller ID." - The problem here is
that if there is a B2BUA in the terminating domain, verification by the UA
is likely to fail.

Section 5 "Similarly, in cases where a proxy serves as a B2BUA and an
ingress proxy, it MUST perform the B2BUA function after the ingress
functions described here." Performing a B2BUA function will invalidate the
Identity header, leading to the problem above.

Section 8, Benefits: "Works in the presence of B2BUAs in the originating and
terminating domains." Well, it only works in the presence of a B2BUA in the
terminating domain if the UAS receives PAI and is prepared to use that in
the face of an invalid Identity header.

Section 8, Benefits: "Provides the cryptographic strengths of SIP identity
to the terminating domain, so that mechanisms such as spam detection can be
effective." OK, to the terminating domain, but not necessarily to the UAS.
Also, not even to the terminating domain if there is an intermediate domain
that uses a B2BUA.

John

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