Hi, Everyone:

The stake for extensions of H.323 to support mobility is so great that people who are familiar with H.323 will be able to understand very easily. Many of those people may not be attending the H.323 Ad Hoc Mobility Group meetings, but they can foresee what I am talking about.

1. Association through Registration with the GK

The registration of H.323 entities with the GK establishes the association such that all information related to terminals/users is passed to the GK. The GK becomes the ONLY source where the information related to the H.323 entities is available. It is very important to note that H.323 does NOT allow any other entities other than the GK to have the association with registration of the endpoints (e.g., terminals) through registration.

This fundamental concept has allowed to define a zone that is managed by a GK. So, the zone has become the building block for H.323. Later on, we have defined domain that contains one or more zones.

All other entities (e.g., BEs) collect this information from the GKs and transfer that information between the BEs in a more efficient way. Please note that even the BEs does NOT have the association with the endpoints (e.g., terminals).

Therefore, the model for extensions of H.323 to support mobility MUST be consistent with Rec. H.323.

2. Intra-Zone and Inter-Zone Communications

When the mobile users move between the cells, the mobility is primarily becomes intra-zone communications because many cells are expected to be controlled by a single GK. At best, two GKs may be involved when mobile users move between the cells. So, intra-zone solution need to be used for inter-zone communications. These solutions are complementary.

So, we have to address the intra-zone communications first before we move to the inter-zone solution. Once we finish intra- and inter-zone communications, we will then move to inter-domain communications because inter-domain communications solution is dependent on the other two.

3. Inter-Domain Communications

In some situations, two BEs of two administrative domains may be involved if mobile users move between the cells.

H.225.0 Annex G defines inter-domain communication via BEs ONLY. This standard does NOT allow to communicate between the two administrative domains with any other entities other than the BEs.

H.323 mobility solution MUST be consistent with Rec. H.225.0 Annex G.

4. Problems for Not Solving Problems Step-by-Step

One bright example is H.225.0 Annex G. BEs are allowed to use the efficient message sets like accessRequest and others, while the GKs cannot. Even it cannot be used between the GK and the BE.

The model is broken from end-to-end perspective. The future of H.323 seems to be very bleak because of this fundamental problem.

Who is to blame?

This has created a fundamental problem to make progress in H.323. Now people are trying to bring contributions to use those efficient Annex G message sets for intra-zone and inter-zone communications, but these contributions are not being accepted because of opposition by a very few.

Do we want create the same problem for H.323 mobility by-passing the step-by-step method creating highly inconsistent solution?

Best regards,

Radhika R. Roy AT&T H.323 Ad Hoc Mobility Group