[H.323 Mobility:] questions on MTD-016

Kumar, Vineet vineet.kumar at INTEL.COM
Thu Apr 13 16:34:00 EDT 2000


Steve,

Thanks for your reply. My comments are embedded in the email below.

vineet

-----Original Message-----
From: Stephen Terrill [mailto:stephen.terrill at ERICSSON.COM]
Sent: Thursday, April 13, 2000 4:42 AM
To: ITU-SG16 at MAILBAG.INTEL.COM
Subject: Re: [H.323 Mobility:] questions on MTD-016


Hi,

I shall try to answer some of these questions below.

Regards,

..//steve



"Kumar, Vineet" wrote:

> Stephen,
>
> I have a couple of questions on your contribution MTD-016. These are:
>
> 1. H.323 already has mechanisms for discovering the gatekeeper. Are you
suggesting in your contribution that the terminal should discover the VLF
instead of the visiting gatekeeper ? Or, are you assuming that the VLF is
integrated in the visiting gatekeeper ?

This can be discussed - I was of the opionion that we should discover the
VLF and send the registration to the home environment after that.  However,
we haven´t agreed on the role of the VLF, and visited gatekeeper, home
gatekeerp and HLF - when we come to agree on what these are, my proposal may
change.

<vineet:begin> Yes, this could be discussed in the conference call. My
suggestion is to reinvent as less as possible. Since we are adding Mobility
to H.323, we should just fill in the gaps that are missing.
<vineet:end>
>
>
> 2. In H.323, authentication of the terminal and the gatekeeper is done at
the time of discovery. In fact, in H.323 all messages between the terminal
and the gatekeeper can be authenticated and the message integrity preserved.
In your contribution, authentication is done at the time of registration.
Why is this preferable to what is already in H.323 ?

I would be interested to understand which gatekeeper you were considering
should do the authentication.  I would assume that the real authentication
would have to be done at home - as such it would be necessary to find the
visited network services, and then register/authenticate at home.

<vineet:begin> I agree with your model but my preference is to preserve the
way H.323 works today in that the authentication of both the user (not
terminal) and the gatekeeper (doesn't matter whether the gk is visisted or
home) can be done at the time of discovery. The protocol between the
terminal and the gk does not change regardless of whether it is the home gk
or the visited gk. The terminal sends its hashed password or certificate in
the cryptotoken field of the GRQ message. The visisted gk tunnels the entire
message to the terminal's Home Administrative Domain for authentication and
authorization. There may be an Authentication Function in the Home
Administrative Domain that authenticates its users. If the user is
successfully authenticated by the Home Administrative Domain then a new
temporary password is assigned by the Home Administrative Domain to the
terminal and the visited gk in GCF for use during that session. This
exchange is explained in detail in the contribution I made for the last
conference call. I can't find the MD #. Does anyone know the MD # ?
<vineet:end>
>
>
> 3. What is the reason for the information flow from the HLF to the home
gatekeeper, and from the home gatekeeperr to the HLF ? I don't think we can
assume that there is only one home gatekeeper that the terminal may be
using. In fact, the home gatekeeper may not have any information about the
user.

I certainly don´t assume that there is only one home gatekeeper.  I assume
that there will be a number of home gatekeepers, but perhaps only one (or
few) HLFs.  In this case, we need an function to select the gatekeeper that
the user is going to camp on - and this may depend on load, subscriber
profile, policy - or a lot of things.

<vineet:begin> I guess I will have to understand the model that you have in
mind regarding the use of a home gk on which the terminal camps on. In my
model the HLF will send all pertinent information about its user to the VLF.
The home gk is not needed.
<vineet:end>
>
>
> Regards,
> vineet



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