Intra Domain/Inter zone communication

Roy, Radhika R, ALARC rrroy at ATT.COM
Wed Nov 3 09:08:57 EST 1999

Hi, Haim and All:

I am glad that you took the pain to go through AT&T's contribution
(APC-1434) submitted a long time ago. You are right. There are some
fundamental issues that need to be addressed for scalability especially for
the large-scale network(s). Let me summarize my personal view point what
progress we have made so far:

*       Inter-Domain Communications:

1. We have finalized the H.225.0 Annex G protocol. HopCount and other
aspects (e.g., distributed and centralized domain concepts, caching
mechanisms [but not how to manage the cache]) of AT&T's contribution were
2. More work needs to be done. For example, seamless communications (e.g.,
signaling messages) between the intra-domain and the inter-domain. How do we
send signaling messages (RAS/Annex G, Call Signaling) among the BEs when
domains are fully distributive (not fully connected)? How do we implement
the application layer H.323 QOS on end-to-end basis using the same QOS
services format from end users' point of view when pre-call or call
signaling messages will go via none (direct), all, or some BEs between the
source-destination domains considering the domains are distributive and each
domain may implement different network layer QOS services? All these issues
are subject to further standardization.
3. More contributions will allow us to proceed in this area in the future.

*       Inter-Zone/Intra-Domain Communications:

1. No modification or improvement has been made in H.323.
2. AT&T contributions have been made to allow the more powerful Annex G
messages for inter-zone communications as well. I request that all companies
examine this proposal.
3. For two-GK model,  I see that the existing signaling messages may work
(even then we have some problems). However, we have, as you have also
pointed out, serious problems in the case of multiple-GK (3, 10, ... )
4. We also need to provide more contributions solving these problems.

*       Going-Forward:

1. We have opened a new work group know as "H.323 Robustness."
2. This group will have to deal with GK reliability as well. In this
situation, we have to consider multiple GKs even in a given domain. We
definitely need an new inter-GK protocol.
3. My suggestion would be: Let us consider the GK architecture and test the
inter-GK protocol. Many of the suggestions made in AT&T contributions may
still be applicable to develop the inter-GK protocol.
4. We may have a valuable experience while we develop the new inter-GK
protocol to improve the robustness.
5. We may then apply the same experience how we can further improve the
existing signaling messages for inter-GK communications as well.

For now, this is what I have to offer to you. Hope that others will also
provide their comments.

Best Regards,
Radhika R. Roy
+ 1 732 420 1580
rrroy at

> -----Original Message-----
> From: Haim Rochberger [SMTP:Haim_Rochberger at EUR.3COM.COM]
> Sent: Wednesday, November 03, 1999 4:36 AM
> Subject:      Q: Intra Domain/Inter zone communication
> I apologize for the wide distribution - I am a "new kid in town".
> I know that Annex G refers to inter-Domain connectivity... but my current
> interest is Inter-Zone/Intra-Domain.
> It is clear that GKs can broadcast  LRQ msg to resolve non-local addresses
> (and
> cache them) , but this does not sound like a scaleable
> solution.
> I found a contribution APC-1434 from AT&T that gives some static and
> dynamic
> solution/guidelines.
> My questions are:
> 1) What is the status of the contribution ? anyone knows if this is
> accepted ?
> 2) Can someone point me to other places in any standard/contribution that
> address this issue (if such exist).
> If no special mechanism exist, and yet people agree that this is an issue
> (scaleability and redundancy) for Inter-Zone
> then let me know, and I can build a contribution  that will offer those
> requirements.
> Yours,
> Haim.
> e-mail: Haim_Rochberger at

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