Douglas:

I agree with you.

We also discussed this topic last year. It is also true that some kind of roaming can be supported the way H.323 (H.323, H.225.0, H.225.0 Annex G, H.245) standards are there. It depends what we actually mean by roaming. There should be some kind of common understandings or standards what kinds of roaming services are to be supported. For example, per call authorzation is one way of satisfying roaming requirements.

Now we need to define the scope or requirements of roaming in a standard way. Accordingly, we have to see how much of these requirements we already can support in the existing standards, and what else we need to develop in standards.

Radhika R. Roy AT&T

-----Original Message----- From: Douglas Clowes [SMTP:dclowes@OZEMAIL.COM.AU] Sent: Monday, April 26, 1999 7:01 PM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: Annex G and Roaming?

Espen,

It all depends on what you mean by "roaming of users between different domains".

Annex G does support some functionality for some favours of roaming, but requires further development - particularly in how to use these aspects between domains.

Comments below. At 14:54 1999-04-23 +0200, Espen Skjæran wrote:

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Hi all,

I've recently heard (unofficially) that some claim Annex G (APC-1546/TD-20 in Monterey) also to support roaming of users between different domains.

If this is true, I wonder how.

I can see how the AccessRequest/ValidationRequest might be sent from a visiting domain to the home domain for per-call authorization. While this might work in simple cases, it will hinder the use of services while roaming.

Per call authorization permits a user from one domain to use gateway equipment from a second domain, to make calls to through a gateway in a third domain. There could even be a fourth domain present as a clearinghouse.

I don't know what you mean by "hinder the use of services while roaming" in this context. Perhaps you could elaborate please.

...

I can not either see any mechanism to authorize the roaming registration.

Registration is a completely different issue, and I don't see support for it in Annex G. Perhaps an RRQ with a remote e.164 or IP address could be issued to the home domain, by the terminal or host gatekeeper?

...

I am sorry to post based on "rumors", but this may change the scope of Annex G significally, and I worry if this might affect future work on roaming. As Tiphon has just started their work on roaming by analysing existing roaming techniques in telco and datacom/IETF work,and not yet reached any conclusion, it seems premature to use annex G in its current state for roaming.

These concepts will have to be developed in parallel. There is more than one "type" or "roaming", and different people will think of different things when that word is used. Some people think of terminal mobility, while others think of mobile IP. Neither of these apply to the mobile user on public ingress gateways depicted above, but they are no less valid and need to be considered.

When we know what the opportunities are, we will be better placed to seek solutions. It is not enough to just say "roaming"!

Douglas

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Espen