Nothing in H.323 prevents the GK from consulting other functional entities when necessary to track the location of a user.  I have been following the discussion from afar, but my impression is that (1) it is proposed to distinguish a domain-specific Location Function in support of user mobility and (2) the work on mobility is partly about how the GK interacts with this function.  It makes sense that the technology of mobile communications -- really just a transport issue from the point of view of H.323 -- should be treated separately from the technology of multipoint multimedia communications, which is what H.323 was designed for.  Moreover, the architectural distinction is useful to avoid undue restriction of the possible business models -- the mobility service provider may well be different from the multimedia communications service provider.

-----Original Message-----
From:   Roy, Radhika R, ALARC [SMTP:rrroy@ATT.COM]
Sent:   Friday, April 14, 2000 10:48 PM
To:     ITU-SG16@MAILBAG.INTEL.COM
Subject:        Should we Break H.323 Model for Mobility?

Hi, Everyone:

H.323 has some definite architectural notion such as terminal, GK, GW, MCU
and(MC, MP). One of the fundamental corner stones is the GK. The H.323
entities (e.g., terminals, GWs) register with the GK. A GK manages a zone
with the information of all registered users along with other functions
(e.g., bandwidth, resource management, etc).

The "registration" with the GK is the fundamental corner stone of H.323
where an association is made by each user. That is, a GK becomes the basic
source to have the information related to each user.

H.323 mobility protocol MUST also follow the same H.323 architectural
concept. If this basic notion is not maintained, it breaks the basic
foundation of H.323.

It appears that H.323 mobility likes to define additional databases like
VLFs and HLFs that will store the information related to the mobile users.
These databases are supposed to help the function of a GK in order to manage
the mobility related information.

If people think that an H.323 will be able to register with a VLF directly,
does it not mean we are by-passing the basic foundation of H.323 model? Does
it not opening the entirely a new set of problems in H.323? It will create a
parallel architecture like GK in H.323 what is not needed at all because
solutions have provided that are consistent with H.323 model and there is no
need to do this. We probably have to do all over again what we have done for
the GKs and BEs. We inviting unnecessary problems that are yet to imagine
where we may end up with. Why do we need to do that if one can do this using
the consistent H.323 model of GK?

In another situation, we have to go step-by-step. First intra-zone, then
inter-zone, and last of all inter-domain. Contributions are there to address
those problems.

The mobile users that move between cells, those cells are expected primarily
remain the control of a given GK (in some cases it may be two GKs). These
scenarios mostly seem to be intra-zone and inter-zone and may involve a
single service provider. Of course, there will also be the calls between the
two adm domains of two service providers.

More importantly, solutions are inter-dependent. That is, we cannot address
the problems of inter-zone without knowing the intra-zone. In the same
token, we cannot address the inter-domain problems without knowing the
inter-zone problem. Contributions are there. Let us proceed accordingly.

Last of all, I am reminding the mess that we have made in Annex G. Now
people are hungry to use the more powerful and efficient Annex G messages
between the GKs. Contributions were brought to do this, but the proposals
had been rejected by a very few. Who is suffering?

Best regards,
Radhika R. Roy
AT&T