Roy, Radhika R, ALTEC rrroy at ATT.COM
Thu Aug 27 10:59:22 EDT 1998


Kindly also wait to get an answer from me as per your proposed
configurations and call flows explained step by step. Let me be settle after
finishing my trip from Washington DC. I hope to get back to you soon.

Thanks and regards,

Radhika R. Roy

> ----------
> From:         Chris Purvis WVdevmt-WS[SMTP:cpurvis at MADGE.COM]
> Reply To:     Mailing list for parties associated with ITU-T Study Group
> 16
> Sent:         Thursday, August 27, 1998 6:15 AM
> Subject:      Re: ARQ/ACF
> 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
> 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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