Usage of CallID in H.323v2 for rerouted (diverted, transferred,.. .) calls

Klaghofer Karl PN VS LP3 Karl.Klaghofer at VS.SIEMENS.DE
Mon Nov 16 06:09:26 EST 1998

H.225.0v2 CallID identifies the call with which the message is associated
(all RAS and Call Signalling messages related to the same call).

Is it allowed that the CallID value for a rerouted call (second Setup) may
be the same as the CallID value used in the first call Setup message ?
According to H.323v2 clause 7.5 second last sentence it is even recommended
(e.g. reference to Fig. 19/H.323 where all messages shown in the figure
shall use the same CallID) ?  However, I would like this to be confirmed,
since somebody might interpret this as contradicting with the definition of
the call identifier.

If we can confirm this, then I propose that such a usage of the CallID is
also possible for H.450.x related call redirections (e.g. Call Diversion,
Call Transfer). This would allow the calls (e.g. first call setup and
diverted call) to be associated for applications.

As an alternative, we might add a new multilevel CallID (e.g. to H.225.0 v3)
that consists of an identifier that indicates the "overal call" and a second
identifier that indicates the call leg.


Karl Klaghofer, Siemens AG, Dpmt. ICN IB NL IP
Hofmannstr. 51, D-81359 Munich, Germany
Tel.: +49 89 722 31488, Fax.: +49 89 722 37629
e-mail: karl.klaghofer at

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