RE: [Sipping] Inserting a B2BUA into an existing dialog

["Dale Worley" <dworley at pingtel.com>]

> From: Paul Kyzivat [mailto:pkyzivat at cisco.com]
>
> The obvious question is: How would C know to do that? Either C is
> already in cooperation with A or B, or else C is operated by
> the user of
> A or B.
>
> The other obvious reaction is that you are trying to institutionalize
> wire tapping. That won't make you popular. (Well, maybe with the FBI,
> but not with people here.)

One possibility is that C is the attendant console in an office PBX, and
e.g. the attendant is setting up a conference call.

Another possibility is that A's UA does not have a conference bridge
capability, but by hitting some keys, a second call can be placed from the
UA to a conference bridge device to activate it.  The conference bridge
device then needs to direct (dumb) UAs A and B to finish the conference
set-up.

> How about:
>
> - C subscribes to dialog event package for both A and B
>    (probably already did to know it wants to do this)
> - C sends an INVITE/Replaces to A with no offer.
> - A responds to the invite with offer SDP1

A sends BYE to B.

> - C then sends INVITE/Replaces to B with SDP1

B responds "No such dialog".

Dale


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