ARQ/ACF

Roy, Radhika R, ALTEC rrroy at ATT.COM
Fri Aug 28 19:03:15 EDT 1998


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.

 <<...>>



> ----------
> From:         Santo Wiryaman[SMTP:swiryaman at VIDEOSERVER.COM]
> Reply To:     Mailing list for parties associated with ITU-T Study Group
> 16
> Sent:         Friday, August 28, 1998 5:46 PM
> To:   ITU-SG16 at MAILBAG.INTEL.COM
> Subject:      Re: ARQ/ACF
>
> Hi Radhika:
>
> You wrote:
>
> 1. Current H.323v2 (e.g., Section 8 with explicit Figures) DOES envisions
> the RAS signaling messages including ARQ can be sent between the GKs in
> addition between the H.323 entities and the GK. (Please note the
> difference with Mr. Purvis reply).
>
> I quickly scanned Section 8 of H.323v2 and could not find the case where
> ARQ's are sent between GK's.  Could you be more specific on which
> sub-section it is in or what figure? That would help me a lot. Thanks.
>
>  -santo
>



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