From: Jonathan Rosenberg <[EMAIL PROTECTED]>

   I have a practical worry on using the Call-ID as a correlator for the 
   subscription. The reality of deployments are many B2BUAs exist, and this 
   is no longer a reliable e2e correlator for things. Anyway its not 
   needed; the URI should be sufficient (and unlike call-id, is reliable). 

(Which URI are you referring to?)

There has been a lot of trouble regarding correlation between CC
subscriptions and orignal calls.  Let us set aside for now the
question of whether correlation needs to be done at all.  The Call-Id
of the original call would be a wonderful correlation identifier, but
as John Elwell pointed out, even now transit networks have many B2BUAs
that change the Call-Id.

Although it is not reflected in draft-ietf-bliss-call-completion-02,
the current thinking is that the URI of the From header would make a
good correlation identifier -- even in the presence of B2BUAs, the
>From URI of the CC SUBSCRIBE and the recall INVITE are very likely to
be identical to the From URI of the original INVITE, all of these
being "as seen at the UAS" -- because B2BUAs are likely to apply the
same transformation rules to all of these requests.

Dale
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