Subject: Questions.1

From: [email-masked] (Lawrence Conroy)
Date: Mon, 30 Aug 1999 13:33:18 +0100

Hi All,
(I think this relates to Scott's earlier posting
 "RE: PINT: Question to SUBSCRIBE/BYE -- I disagree"

> ...snip...
>        b. both methods must be supported anyway: In SIP, you may
>issue new requests with an old call-id, and we have a requirement to
>enable third-party monitoring, which implies a requirement to have new SIP
>call-legs to refer to an ongoing PSTN call.
)

Um... This Is PINT, not SIP. The reactions a node may get in practice may
be different, IMHO.
I do have a question for clarification on what happens if you "issue new
requests with an old call-id". Comments gratefully received.
--------
In PINT, if a PINT Client sends a BYE message with a (CallID, To and From)
tuple that matches a prior Invitation, then this may be rejected by the
recipient Gateway. This is because it may not be possible to cancel a
service request after it has been submitted to the IN/GSTN for processing.

Also note that, in PINT, it may not be acceptable to receive a new INVITE
for the same CallID; the service request may have been submitted to the
IN/GSTN, in which case it may not be possible to change the request. Thus,
although SIP allows a Re-INVITE to change the parameters of a session, this
may not be practical with PINT.

[As an aside, I rather wonder what the effect will be if a "straight" SIP
Re-INVITE is sent to a SIP VoIP/PSTN Gateway, as there it may not be easy
to change the PSTN side of a call.]

In effect, one can consider such Re-Invitations within SIP as a combination
of an implicit BYE followed immediately by a new INVITE (using the same
CallID but a higher CSeq).
----
Question - should PINT Gateways treat a Re-Invite in this way (i.e. they
have been asked to cancel an earlier service request and to accept a new
one)?

If so, should the Gateway treat the BYE implicit within the Re-Invite in
the same way as an explicit BYE (i.e. to reject the message if the earlier
service invocation cannot be cancelled)?

All the best, Lawrence
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| Lawrence Conroy,    | "These Opinions must be mine, 'cos if they    |
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