Hi, Jaakko:

I am providing a very quick response because we will have the conf call within 45 minutes.

First, H.323 has the abstraction of network address (or point of attachment). So, all contributions of AT&T and other companies refer to that only.

Second, the H.323 mobility protocol proposed by AT&T, Alcatel or others do NOT tie to any topology. The topology shown has come into play to provide descriptions so that people can understand, and we can say all requirements are met no matter what the topoloy is. For example, your contribution and references figures - we need to see whether all toplopies can be satisfied using the SAME protocol.

Third, no contribution (AT&T, Alcatel, or Ericsson) has suggested that HLF or VLF has to belong to a zone or by couple of zones or otherwise. All contributions are saying that HLFs and VLFs are behind the GKs.

I hope that you will NOT mis-interpret the intend of the main idea behind the contributions.

Again, protocols defined is NOT dependent on any topology. The contribution shows how the protocol can satisfy when this is used in the context of any topology that people can think of so that nothing is missed from the protocol.

Best regards, Radhika R. Roy AT&T

-----Original Message----- From: Jaakko Sundquist [SMTP:jaakko.sundquist@nokia.com] Sent: Monday, April 17, 2000 9:43 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: [H.323 Mobility:] Comments to various mails

Hi all,

It certainly seems that we have some discussion going on in the reflector. I haven't read the mails since thursday and there really has been a flood of them, so I'll try to gather all my comments in this message.

Radhika, thanks to our discussions last week I have finally understood your intentions on a couple of issues. First the issue of home/visited network. I think I now understand what you mean when you say that a zone may include more than one network (a part of the zone runs on IP and another part on ATM for instance), but I still fail to see, why we should define such concepts, the H.323 layer should not really be concerned what the underlying network type is. Furthermore, you made the argument that since H.323 has defined the topology of the H.323 systems in terms of network address/zone/domain we should also define home/visited network address/zone/domain. I do not agree on this. So far I have not seen any reason for defining any other of these concepts than the already defined Home/Visited Administrative Domain. The only important issue with these home/visited concepts in my mind is the location of the HLF of the user and I would argue that the entity administering some part of the network should also own the HLFs in that part of the network. Thus defining the Home Administrative Domain of a user as the Domain that contains the HLF of the user makes sense, but since we are not binding the HLF to any particilar zone or network we do not need to define or use the terms home zone/network. Secondly, I think I understand, albeit somewhat vaguely, now, what exactly you are meaning with Intra-zone, Inter-zone and Inter-domain communications. The difficulty with these terms in the context of Annex H is, however, that traditionally these terms have been used in H.323 only when there is a call involved. In other words, we haven't talked about e.g. an Inter-zone registration procedure previously in H.323. The problem when using (at least) the terms Intra/Inter-zone with the Annex H work is that we have not made any assumptions about the relationships of the mobility functional entities and zones, i.e. a VLF or a HLF is not defined to be a part of any zone. Thus, when you are talking about Inter-zone or Inter-domain communications for e.g. the terminal/user registration or location updating procedure, what exactly are you meaning? My guess is that the division that you are referring to, is based on the previous location of the User, i.e. in the same zone or another zone, am I correct? Anyway, I'm quite sure that we need to address all the issues that you are thinking of, but dividing the work in steps defined by the Intra/Inter-zone/domain communications is not the best approach in my opinion.

Steve, I think that we need to clarify the issue of home/visited domain execution of services, so that both of these models are understood by all the members of the group. Maybe some co-work could be done by us?

As for the discussion on "not breaking up the current H.323 model", I'll just say that I share the opinion that all registrations, etc. should be done via the gatekeeper in order to preserve the old H.323 model. I see no point in doing the registration straight to the VLF. I'm not quite sure, what Steve's contribution was all about in this respect, but we'll probably be discussing that in the teleconference.

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Jaakko Sundquist * +358 50 3598281 * Audere est Facere! jaakko.sundquist@nokia.com *

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