Subject: Handling of Setup message by Gatekeeper.

From: [email-masked]
Date: Tue, 9 Mar 1999 13:00:47 +0530

Hi All,
       Here is a query regarding handling of setup message received by
Gatekeeper.

In normal case, any endpoint in the zone of a gatekeeper will send ARQ
message before sending Setup message. On receiving ARQ, Gatekeeper will
check for registration, allocate bandwidth and also decides the callmodel.

But there are cases when Gatekeeper receives Setup without receiving ARQ
from an endpoint. Scenarios include:
1. Called party Gatekeeper decides for GKrouted call model and sends ARJ.
Called endpoint sends facility message with reason = routeCallToGatekeeper
to the calling party. In this case, calling party releases the previous
call and sends a new Setup message to the called endpoint's Gatekeeper.
2. If calling and called endpoints are registered with different
gatekeepers and called party's gatekeeper decides for GKrouted call model.
Calling endpoint, registered with gatekeeper1, will send Setup to
gatekeeper2 while it has performed ARQ/ACF transaction with gatekeeper1.
3. GK receives Setup message from another gatekeeper.
4. GK receives a Setup message from a gateway in preGrantedArq scenario.

In all these cases, gatekeeper will receive Setup message without receiving
ARQ message. So how can gatekeeper check whether ARQ is expected from the
endpoint, which sent the Setup or not? No field in the Setup message seem
to give this information. If gatekeeper doesn't check for this, that means
even the endpoints in its own zone can bypass gatekeeper for RAS
signalling?

Any help/information on this issue will be appreciated.

Thanks,
Ritu.
_____________________________________________________________________
Ritu Gupta                                   |       email:
[email-masked]
Senior Software Engineer,       |                   [email-masked]
Hughes Software Systems,     |       phone: 91-80-2286390/91/92(W)
Banglore, Karnataka                  |                    91-80-3374075(H)
INDIA.                                           |       Fax  :
91-80-2286393
_____________________________________________________________________
Restlessness and discontent are the first necessities of progress.

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From: "ronald h. davis" <[email-masked]>
Date: Tue, 09 Mar 1999 12:02:19 -0600

[email-masked] wrote:
			[scenarios deleted]
> Any help/information on this issue will be appreciated.

the gatekeeper is only responsible for arq/acf/arj with endpoints within 
its zone.  all endpoints within the zone establish a ras channel (over
which these messages are sent) with their gatekeeper.

endpoints in other zones don't establish a ras channel with this
gatekeeper.  thus, when calls are received from outside of the zone
the recipient (be through the direct or gatekeeper routed call model)
has no idea how the calling endpoint came upon sending the setup
message.

this statement may be controversial but it is my opinion that h.323
is lan-oriented, so if you think of gatekeepers as administering
bandwidth allocation, &c for endpoints on different lans it would
be difficult for a gatekeeper to perform this administration for
a different lan.  and it would be even harder for a gatekeeper to
perform such administration over a wide area network consisting of
a number of zones.

this fact leads me to believe that the ras channel should be *optional*
for h.323 gatekeepers.  to abstract your scenarios further it is
possible that gatekeepers could act as application layer routers, in
which case they are terminating h.225 signalling and h.245 media control
channels for endpoints with which they have no ras channel.

-- 
  __  ______  __  / __/ |       lucent technologies, naperville il, usa
_/ (_(_) / (_(_/_/_(_/  .       [email-masked]
"if you ain't the lead dog, the scenery never changes"  -- edmund wilson

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