Subject: [Sip] Isomorphic Request Definition

From: "McMurry, Kathleen" <[email-masked]>
Date: Mon, 22 Oct 2001 15:27:04 +0000

The definition of an Isomorphic Request was changed in one of the bis drafts
to include the top-most Via header.   My question regarding this is
two-fold:

1) What call flow is it that requires the top-most Via header to be a part
of this definition?  The only reference to this I have seen is in the
"Changes made in Version 02" section.  That section indicates that "the
Request-URI is the same for all BYE requests that are record-routed".  This
doesn't seem to be the case if the procedures detailed in Section 16.3 are
followed.  That section indicates that "the URL placed into the Record-Route
header MUST be unique for each unique Request-URI in the request". 

2) If there is a call flow that requires the top-most Via header to be a
part of this definition, what is the appropriate behavior of a Proxy Server
or UAS if the Request-URI, CallID, From, To, and CSeq are the same in a
Request, but the top-most Via header is different?  Some kind of error
response?  

Thanks in advance for the clarification.

Kathleen McMurry