-----Original Message-----
From: Roy, Radhika R, ALTEC [SMTP:rrroy@ATT.COM]
Sent: Friday, August 28, 1998 7:03 PM
To: ITU-SG16@MAILBAG.INTEL.COM
Subject: Re: ARQ/ACF
Hi Santo:
Section 8.1.6.(3/27/98 - Contact Person G. Thom - Editor) - Thanks,
Radhika
8.1.6 Optional Called Endpoint Signalling
The procedures defined in 8.1.4 and 8.1.5 show that when a called endpoint
is registered to a Gatekeeper, a Setup message is initially sent to the
called endpoint from the calling endpoint or the calling endpoint's
Gatekeeper. If the called endpoint's Gatekeeper wishes to use the
Gatekeeper
routed call model, it returns its own Call Signalling Channel Transport
Address in the ACF. The called endpoint then uses the Facility message to
redirect the call to the called endpoint's Gatekeeper's Call Signalling
Transport Address. These procedures assume that the calling endpoint or
calling endpoint's Gatekeeper only knows the called endpoints Call
Signalling Channel Transport Address. This address may have been received
in
an LCF sent in response to an LRQ requesting the address of the called
endpoint or it may be known through out of band methods.
If the called endpoint's Gatekeeper desires a Gatekeeper routed call
model,
it may return its own Call Signalling Transport Address in the LCF. This
will allow the calling endpoint or calling endpoints Gatekeeper to send
the
Setup message directly to the called endpoints Gatekeeper, thus
eliminating
the redirection process.
An example of this scenario is shown in Figure 24/H.323. In this example,
both endpoints are registered to different Gatekeepers, and both
Gatekeepers
choose to route the call signalling (similar to the case in Figure
23/H.323). Endpoint 1 (calling endpoint) sends an ARQ (1) to Gatekeeper
1.
Gatekeeper 1 multicasts an LRQ(2) to locate called Endpoint 2. Gatekeeper
2
returns an LCF(3) with the Call Signalling Channel Transport Address of
itself. Thus, Gatekeeper 1 will subsequently send a Setup (6) message to
Gatekeeper 2's Call Signalling Channel Transport Address and Gatekeeper 2
will send a Setup (8) message to Endpoint 2. Endpoint 2 initiates the ARQ
(9)/ACF (10) exchange with Gatekeeper 2. Endpoint 2 then responds to
Gatekeeper 2 with the Connect (12) message which contains its H.245
Control
Channel Transport Address for use in H.245 signalling. Gatekeeper 2 sends
the Connect (13) message to Gatekeeper 1 which may contain the Endpoint 2
H.245 Control Channel Transport Address, or a Gatekeeper 2 (MC) H.245
Control Channel Transport Address, based on whether the Gatekeeper 2
chooses
to route the H.245 Control Channel or not. Gatekeeper 1 sends the Connect
(14) message to Endpoint 1 which may contain the H.245 Control Channel
Transport Address sent by Gatekeeper 2, or a Gatekeeper 1 (MC) H.245
Control
Channel Transport Address, based on whether the Gatekeeper 1 chooses to
route the H.245 Control Channel or not.
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