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

[Roy, Radhika R, ALARC]

Hi, Steve:

In H.323, GKs are the communication entities thorough which registration and
other services are obtained by users while VLFs and HLFs are used ad
databases to store the information that are appropriate related to the
mobility management.

In H.323, a user is always associated with a GK through registration, and a
GK manages a zone where all its H.323 registered users reside. In addition,
a GK also manages resources of the zone.

Please also see the mobility management information flows in AT&T
contributions MD-017 and MD-018 how the GK is involved to resolve
information via VLF and HLF.

A mobile user MAY like to differentiate between a home GK and a foreign GK
(security and many other reasons). It is an OPTION, not mandatory.

Hope this clarifies your questions.

Best regards,
Radhika

-----Original Message-----
From: Stephen Terrill [mailto:stephen.terrill at ERICSSON.COM]
Sent: Friday, April 14, 2000 8:02 AM
To: ITU-SG16 at MAILBAG.INTEL.COM
Subject: Re: [H.323 Mobility:] questions on MTD-016


Hi Roy,

Can you please clarify why the gatekeeper selected for the services is a
"user" issue?

Regards,

..//steve

"Roy, Radhika R, ALARC" wrote:

> Hi, Vineet and Steve:
>
> I like to add couple of points with respects to your emails as follows:
>
> HLF:
>
> It is interesting to note that there appears to be an "implicit"
assumption
> that there is only one HLF in a domain (no matter what happens in the
> future).
>
> Let us NOT make our protocol "hard-wired" like this.
>
> The protocol should be flexible enough to accommodate one or multiple HLFs
> in a domain.
>
> If one wants to choose one HLF per domain, it MUST be left as an
> implementation issue, NOT a protocol issue.
>
> Home GK:
>
> In the same token, if one wants to declare a GK as its home GK, this
option
> MUST be provided to a user. It is a choice that MUST be given to a user.
If
> anyone does NOT like this option, they MAY not use it.
>
> Home Network/Network Address:
>
> In the same token, if anyone wants to declare a network address as its
home
> network, this option MUST also be provided.
>
> GK Discovery:
>
> The "old" inefficient GRQ discovery mechanisms may not be the only OPTION
to
> discover the GK. in a highly mobile cellular environment. An alternative
> mechanism, like MGA message can be listened to discover the GK as well.
>
> Best regards,
> Radhika R. Roy
>
> > -----Original Message-----
> > From: Kumar, Vineet [SMTP:vineet.kumar at INTEL.COM]
> > Sent: Thursday, April 13, 2000 4:34 PM
> > To:   ITU-SG16 at MAILBAG.INTEL.COM
> > Subject:      Re: [H.323 Mobility:] questions on MTD-016
> >
> > 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