Issue with APC-1804

Callaghan, Robert Robert.Callaghan at ICN.SIEMENS.COM
Mon Jun 12 09:48:08 EDT 2000


The definition of the global call reference is a value that represent all
call references on a link.  Q.931 limites this to STATUS, RESTART, and
RESTART ACK in that these are the only messages that can have global
context.  It would be valid for H.225.0 to extend this to any message that
can reasonable have a global context (Remember this is not Q.931).  The
proposal is the use the FACILITY Message to indicate the ability of the
link; that is all call references on the link.  This seems reasonable.


Robert Callaghan
Siemens Enterprise Networks
Tel: +1.561.923.1756    Fax: +1.561.923.1403
Email:  Robert.Callaghan at

-----Original Message-----
From: Paul E. Jones [mailto:paulej at PACKETIZER.COM]
Sent: Monday, June 12, 2000 2:53 AM
To: ITU-SG16 at
Subject: Issue with APC-1804


APC-1804 describes how an entity may signal its current ability to handle
multiple connections over a call signaling channel.  The intent is for this
to be a dynamic capability.

Two issues:
1) This has been proposed for the H.323v3 IG.  Will there be any backward
compatibility issues?
2) The text of the proposal (as agreed and further truncated my me) reads:

``An entity may dynamically set the value of the multipleCalls field in
order to indicate its present ability to support multiple connections along
the Call Signalling Channel. If an endpoint wishes to change the value of
multipleCalls at a time when no other H.225.0 messages are being exchanged
across the call signalling channel, it shall transmit the multipleCalls
field via a Facility message and the CRV shall be the Global Call Reference
as shown in Figure 4-5/Q.931.''

The desire was to use the Global Call Reference value to indicate a change
in this capability when no messages are being exchange.  It was also
proposed that the Facility message shall be used.  However, I believe that
Q.931 limits the Global Call Reference value to being used with Status,
Restart, and Restart Acknowledge.

Is this a point that may become an issue for us in the future or is it
acceptable that we are using the Facility message with the Global Call
Reference when Q.931 forbids such use?  (Perhaps I am wrong on this point..
I invite the correction!)


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