ARQ/ACF

Chris Purvis WVdevmt-WS cpurvis at MADGE.COM
Thu Aug 27 07:15:37 EDT 1998


WanJiun,

The important fact about GK in your diagram is that it is an MCU, not
that it is a gatekeeper.  The functionalities are separate, and
inter-zone calls are possible.  Hence, in answer to your specific
questions:
1. There is no reason in the standard why an MCU needs to be in the same
zone as any of the endpoints is is joining in a conference.
2. ARQs are not (in current versions of the standard) transmitted between
gatekeepers.  They are ONLY transmitted from an endpoint (where gateways,
proxies, MCUs etc are endpoints in this sense) to the gatekeeper with
which it is registered.  However, the MCU should send an ARQ to its
gatekeeper asking whether it should accept the call, and it is up to the
MCU's gatekeeper to permit or deny authorisation to use resources in its
zone.  In your diagram the MCU and its gatekeeper are co-located, so the
ARQ per se might not be sent, but the MCU "part" will still be expected
to ask the gatekeeper "part" whether or not it should accept the call.
However, there is no guarantee that talking about resource usage "within
a zone" is useful, due to the fact that a zone has logical rather than a
physical scope.

I hope this clears up your queries.

Chris
----------------------------------------
Dr Chris Purvis - Senior Development Engineer, WAVE CC Software
Madge Networks Ltd, Wexham Springs, Framewood Road, Wexham, Berks.
Phone:+44 1753 661359  email: cpurvis at madge.com

Roy,

    Sorry, I just joined, and maybe have missed the disscussion of the
following questions. I am a bit confused about how they are handled.

----
In a distributed gatekeeper architecture of multiple zones environment,

say, the H.245 control channel topology looks like as follows:

       E1 ----- GK -------E2
               / | \
              /  |  \
             /   |   \
            E3   E4  E5

E1 is in zone 1, E2 is in zone 2, and (E3,E4,E5) are in zone 3.
(the corresponding gatekeeper in each zone is denoted to GKi)

GK is a gatekeeper that contains an active MC for multipoint conference
ocntrol.

1. Should GK has to be in one of {zone1, zone2, zone3)?

2. If endpoint F in in zone 4 would like to join the conference,
     F must send an ARQ to GK4 before any setup to join the conf.
(because
     GK4 is in charge of the admission for call bandwidth etc. local
     resources.)
   Should GK4 forwards ARQ to GK that has the MC?? F should not use any
   resources in the zone of GK is responsible for.
or F has to, because H.245 control message exchanges also consume the
   reources?
or some others?

Please advise. Thanks a lot.

Regards,

Vivian Liao



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