Roy, Radhika R, ALTEC rrroy at ATT.COM
Fri Aug 28 17:18:58 EDT 1998


I am extremely happy in seeing Mr. Clowes answers. I am also adding a little
text in Clowes' answers to clarify further in relation to the proposed
AT&T's distributed model.

I am using one of your assumptions is that MCU is located in zone that has
its own GK. In H.323, each GK manages resources in its own zone.

Now MCU will be acting as the central point that will be controlling the
call. That is, a calling H.323 endpoint will set up a call with the MCU, and
in turn MCU will set up the call with the called H.323 endpoints. If a new
H.323 endpoint located in new zone wants to join the conference, it will
also contact the MCU.

Now the RAS signaling messages between the GKs will be following the similar
logic. That is, from the calling H.323 endpoint's GK to the MCU's GK, and
then from MCU's GK to the called H.323 endpoints' respective GKs, etc.



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).
2. In "logical" zone environment, the resource management is also extremely
important especially in the context of large network where million of users
share the same physical network (e.g., in carrier networks, in virtual
private networking environment, the network reosources are partioned
logically between the corporate customers, and resource managemnt is also
done accordingly). [Please note the difference with Mr. Purvis reply].

> ----------
> From:         Douglas Clowes[SMTP:dclowes at OZEMAIL.COM.AU]
> Reply To:     Mailing list for parties associated with ITU-T Study Group
> 16
> Sent:         Thursday, August 27, 1998 6:00 PM
> Subject:      Re: ARQ/ACF
> At 12:30 27/08/98 +0800, you wrote:
> >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.
> I find it best to view these as separate entities. Then you can see that
> is
> is the MCU that sends messages to its own gatekeeper, not the other
> members
> of the conference.
> >
> >1. Should GK has to be in one of {zone1, zone2, zone3)?
> There is no reason why all entities should be in any zone, either all in
> the same zone, or all in different zones.
> There is no absolute reason why the MC has to be in the same zone as its
> colocated gatekeeper, even though it may make sense to do so.
> >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.)
> This is correct.
> >   Should GK4 forwards ARQ to GK that has the MC?? F should not use any
> >   resources in the zone of GK is responsible for.
> Not normally.
[Radhika: As I have mentioned in the begining, the communication will be
done between the MCU and the H.323 endpoint. So, the call will span at least
two zones: Zone of MCU and Zone 4 of F. Each GK manages resources in each
zone. As a result, GK of Zone 4 will not be able to confirm the ARQ message
because it does not know about the resources of Zone of the MCU. Accordance
to AT&T's proposed distributed model, GK4 of Zone 4 will send the ARQ
message to the GK of (MCU) zone after cinfirming its own resources. As soon
as the (MCU) GK confirms the resources of its zone, ACF message will be sent
from the (MCU) GK to the GK4 of Zone 4. GK4 then sends the ACF message to

> >or F has to, because H.245 control message exchanges also consume the
> >   reources?
> Endpoint F should receive an ACF from its own gatekeeper, relating to
> resource and policy in its own zone. It should then establish a call
> signalling channel and send a SETUP to the MC. The MC will send an ARQ to
> its own gatekeeper, to request resourse allocation in its own zone, for
> this part of the conference.
[Radhika: According to AT&T's proposed distributed model, it will be
preferable to follow the ARQ/ACF signaling paths as mentioned above by me.
Then, the call signaling SETUP message should be sent to the MCU (because
one of the main puposes of the ARQ message is to confirm the resource
between the source-destination path).]

> >or some others?
> >
> >Please advise. Thanks a lot.
> >
> >Regards,
> >
> >Vivian Liao
> >
> >
> Regards,
> Douglas

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