overlapped Sending in h.323

Sudharsana Krishnan pskrish at miel.mot.com
Tue Aug 10 05:06:40 EDT 1999


The Gatekeeper in my opinion cannot resolve absence of destination
alias to any valid address. You will always receive a ARJ. The first
ARQ you sent should have had the incomplete dest alias and not
NULL. You follow the ARJ with additional ARQs as and when
you keep getting additional information about the destination
and when finally the gatekeeper can translate this address,
it will send you a ACF with either its own Call sigannling
address (Gk routed) or any other.

For eg. Lets assume Ep1 is a terminal connected to a LAN
and supports H.323 with overlapped sending.
The User wants to dial 91-80-5598615. As and when the user
dials each digit (or a set of digits) it sends out a
ARQs to its Gatekeeper with destination alias set to
say 9 (first ARQ) , 91 (second ARQ) , and so on.

Lets assume that the Ep1's gatekeeper has an entry that
maps 91-80 (prefix) to a Gateway's call signalling address,
the Gatekeeper sends an ACF for the ARQ that contains
"91-80" as the destination alias. The ACf can contain the
Gatekeeper's Call Signalling address (if the Gatekeeper
routes the call) or the Gateway's Call signalling address,
and then the Setup, setup acknowlegde, information
message sequence takes over.

Hence the setup goes only after the ACF is received
and only one ACF is received by Ep1 and not two as you
have indicated

Hope this helps


-----Original Message-----
From: Christian Geng <christian.geng at detewe.de>
To: ITU-SG16 at mailbag.cps.intel.com <ITU-SG16 at mailbag.cps.intel.com>
Date: Tuesday, August 10, 1999 1:29 PM
Subject: overlapped Sending in h.323

>Dear Sir or Madam,
>I try to be H.323 conform in the folowing:
>I want to support overlap sending within gatekeeper-routed calls.
>My session starts with a ARQ from enpoint_1 to GK without any
>destination alias. After receaving ACF endpoint_1 sends SETUP without
>any destination alias, but with canQverlapSend is TRUE. GK will answer
>with a SETUP ACKNOWLEDGE. Endpoint_1 will then send digit by digit of
>alias in destinationInfo field of ARQs. By each sending the total
>cumulative addressing information is transmitted in destinationInfo
>field. GK responds each time with an ARJ until recept full destination
>alias, in this case it answers with ACF. I hope I am right until now?
>Reading clause 8.1.12 of ITUs H.323 I thought endpoint_1 shall then send
>a SETUP message to GK? This will be the second SETUP, because enpoint_1
>allready did. Can't GK send now a SETUP to endpoint_2 with the
>ip-address belonging to the destination alias put in the
>destCallSignalAddress field?
>I thank you much for an answer to solv my problem.
>Christian Geng

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