H.323 Annex I

Barry Aronson baronson at ieee.org
Wed Nov 24 09:49:02 EST 1999


Ed,

(First, I assume you mean H.323 Annex I when you write H.246 Annex I.)

Regarding H.323, I don't see at all how Annex I is dependent on Annex H. In
fact, they are (and should be) orthogonal.

Put simply, Annex I deals with everything from H.225, inclusive, on down in
the context of error prone channels and mobile environments (e.g., cellular
networks). This includes IP. There may be some recommendations regarding
error resiliency in the codecs, but this should be approached cautiously.
Ideally, an H.323 application will use exactly the same interface and
messages currently used with regard to H.225 as it will when enhanced with
Annex I. The changes will be quite localized, which will help with adoption
and interoperability with existing systems. Annex I will be extremely useful
without Annex H because H.323 defines a very simple call model that utilizes
the Network Address and Call Signaling Channel TSAP Identifier of the called
terminal -- no gatekeeper is needed. With Mobile IP name services don't have
to be updated. In fact, Gatekeepers could be used with Annex I by using
Mobile IP and automatic Gatekeeper discovery (presumably, a cellular
terminal has been thoroughly authenticated long before having an IP
connection). Even if this model is never used, separating Annex I in this
way is greatly beneficial from a standards development point of view. Work
can proceed without being affected by other development.

Annex H deals with a terminal, user, or service that has moved either
discretely or continuously. Clearly, user and service mobility can occur in
a non-wireless setting. Therefore, there should be no dependency on Annex I
for these functions. Conversely, there is no reason to address user and
service mobility in Annex I. Terminal mobility may occur without the
functionality provided in Annex I. For example, there could exist a large,
homogeneous IP network running on Ethernet in which it was possible to move
one's laptop from one link layer point of attachment to another and cause a
change in IP address (due to being in a different subnet) and H.323
Gatekeeper zone, but still be a functioning host (through DHCP, etc.). Now,
in this situation, Annex I could come into play since Mobile IP falls under
Annex I and Mobile IP could deal with the changed IP address. However, this
may not be the best solution. Since the new IP address will remain in effect
until another discrete location change (ignore dynamic IP addresses as this
problem exists for stationary terminals), it seems more efficient to update
the name servers or Gatekeepers than to use Mobile IP. The question is, what
procedures can be defined in Annex H that would assist this? Also, these
techniques do not necessarily have to be efficient in the cellular world
(Annex I will take care of that situation) since having an efficient way to
deal with semi-permanent (hey, an oxymoron!) subnet changes would be a huge
win.

Although I started by stating that Annex I and H were orthogonal, it seems
there is an overlap in the area of terminal mobility. This gets back to the
original division proposed by Dale in Santiago: Annex I was to be Terminal
Mobility and Annex H User and Service Mobility. If we went back to that, it
might simplify things. On the other hand, there is a rational for dividing
along the lines of  radio-link/cellular/mobile vs. generic mobility, even if
terminal mobility was covered in both. Resolving conflicts would be easy.
Just insert statements like "when connected via radio link and/or the
network point of attachment could change during a call, the procedures
defined in Annex I shall be followed". But then again, it would be nice if
there was a clear procedure in one recommendation that dealt with terminal
mobility. Thoughts anyone?

Barry Aronson
Toshiba Corp.
33 Lake Shore Dr.
Beverly, MA 01915-1907
USA

Voice:  +1 978 232 3994
Fax:    +1 978 232 9220
Mobile: +1 978 902 0768 (mostly worldwide)
E-mail: baronson at ieee.org
H.320 and H.324 video conference available on request

> -----Original Message-----
> From: Mailing list for parties associated with ITU-T Study Group 16
> [mailto:ITU-SG16 at MAILBAG.INTEL.COM]On Behalf Of Edgar Martinez [1]
> Sent: Tuesday, November 23, 1999 9:37 PM
> To: ITU-SG16 at MAILBAG.INTEL.COM
> Subject: Re: H.323 Annex I
> Importance: High
>
>
> Dear All,
>
> I concur, with most of the attached email.
>
> And I have just a couple of comments. Until we resolve the pure case
> of H.323 mobility and  Interworking with PLMN in the application
> layer. H.246 Annex I and Annex E will be delayed, I believe that
> Annex I and Annex E are depended on H.323 Annex-H. Because,
> the required parameters and network functions for the H.323 pure
> mobility and Interworking case needs to be defined in H.323
> Annex-H. And expanded in H.246 Annex-I and Annex-E.
>
> If we do not get the H.323 mobility and interworking
> parameters and functions defined, H.246 annex-i and annex-e
> will be working in the dark.
>
> Because of the H.323 framework that we have to use
> (already defined e.g., GK, GW, Terminals etc.)
> and the already defined mobile networks (e.g., GSM, ANSI-41, GPRS)
> we need to  work top-down (not) buttom-up.
> Lets focus on H.323 Annex-H to make sure that it has the
> network elements that can be re-used in H.246 Annex-I
> and Annex-E.
>
> Ed
>
> "Roy, Radhika R, ALARC" wrote:
>
> > Hi, Everyone:
> >
> > We have now three annexes related to mobility:
> > *       H.323 Annex H: User, Service, and Terminal Mobility in H.323
> > *       H.323 Annex I: Packet-based Multimedia Telephony over
> Error Prone
> > Channel
> > *       H.246 Annex E: Interworking between Existing H.323 Systems and
> > Existing Mobile Networks
> >
> > Per my earlier email, I promised that I would be providing some notes
> > related to Annex I: Packet-based Multimedia Telephony over Error Prone
> > Channel.
> >
> > Every Annex in H.323 has some direct relationship to the H.323
> application
> > layer. Even the informational Appendix II - "Transport Level Resource
> > Reservation Procedures" - shows how the RSVP messages are being
> used in the
> > context of H.323 signaling messages.
> >
> > The way Annex I has been structured shows that it will provide
> information
> > related to bit rate, bit error rate, delay, jitter, and IP
> issues related to
> > radio networks (e.g., mobile IP [home/care-of IP, home/foreign
> IP network]).
> >
> > I understand that additional error correction and concealment techniques
> > that may help specifically H.323 are the main purpose of this annex. My
> > guess is that these proposed concealment techniques will be
> used somewhere
> > below the H.323 layer. If it is so, is not the case that H.323
> does not need
> > to be aware of these lower layer techniques?
> >
> > Now the question is: Can this work of Annex I be directly related to the
> > H.323 application layer signaling messages?
> >
> > If the answer is yes, the next question is: Is this present structure of
> > Annex I good enough to satisfy our objectives?
> >
> > If the answer is no, will it be very helpful in H.323 even as
> informational
> > annex?
> >
> > However, I see that there is an additional scope related to this work of
> > Annex I to the H.323 layer signaling messages. IP related
> issues can be the
> > major topic that will really be very useful to relate the network layer
> > signaling schemes in mobile environment (e.g., mobile IP) to
> those of the
> > H.323 mobility.
> >
> > In this context, I see that there are some works that have been
> performed
> > related to the IP networking in mobile environment. It appears
> that mobile
> > IP has some problems: 1. If the mobile host moves very frequently and 2.
> > Inefficiency for keeping too many reserved IP addresses in the
> pool by the
> > foreign agent for allocation to mobile hosts.
> >
> > To work around those problems, there has been enhancement of mobile IP
> > (e.g., cellular IP) complementing the mobile IP solution.
> >
> > The important point is that they have been using the concept of
> cells, cell
> > IDs, and network IDs packet-switched based IP mobile networking
> environment.
> > A cell can be pico-, micro-, and macro-cell depending on the radio range
> > which is a function of power. Cells are usually inter-connected
> by the LAN
> > in the case of IP networking.
> >
> > (By the way, none has used the concept of so-called location area [LA]
> > concept in the IP networking either in the mobile IP or in the
> cellular IP.
> > I am curious to know why these prototype products and network
> architectures
> > do not contain the concept of LA? Can anyone provide more insights about
> > this? Personally, I would love to relate the LAs with cells.
> Indirectly, it
> > may also help to inter-work with that of the circuit-switched based
> > cellular-PSTN network.)
> >
> > The important point is that we can start with the existing standard of
> > IETF's mobile IP/cellular IP. We can see that switching a cell during
> > communications does not always mean changes in IP addresses.
> That is, this
> > handover (at layer 2) may be transparent to the IP network
> layer (layer 3).
> > No resources in the IP layer will be affected. If the switching in cells
> > causes the change in the IP address during communications, the
> handoff will
> > cause the resource allocation and de-allocation in the IP layer
> during and
> > after handoffs.
> >
> > Extending the same analogy, we can assume that switching of the
> cell may or
> > may not cause any change in the H.323 application layer. If it
> affects the
> > H.323 layer, the resources in the H.323 layer have to be allocated and
> > de-allocated in the H.323 layer during and after the handoff.
> >
> > The other important concept is that the cell IDs can also be related to
> > H.323 zone IDs and so on.
> >
> > It appears that the mobility solution can be related to the link layer
> > (layer 2) to the network layer (IP layer) mobility and the
> H.323 application
> > layer and vice versa. As a test case, people may also try to see how the
> > application layer H.323 mobility solution (e.g., APC-1651,
> APC-1646) can be
> > implemented to the network/link layer mobile/cellular IP solution
> >
> > In this way, I see a wonderful ray of light how the work of
> Annex I can be
> > related to that of Annex H.
> >
> > Last of all, I would request the editor to expand the scope Annex I. If
> > needed, I may also propose to include this item in the upcoming/future
> > conference call.
> >
> > In the same token, I may also provide some comments related to
> H.246 Annex E
> > in the future.
> >
> > I would request all SG16 members to look into this proposal and
> help us with
> > their comments.
> >
> > Best regards,
> > Radhika R. Roy
> > H.323 Ad Hoc Mobility Group
> > AT&T
> > +1 732 420 1580
> > rrroy at att.com
>
> --
> Edgar Martinez - Principal Staff Engineer
> Email mailto:martinze at cig.mot.com
> FAX 1-847-632-3145 - - Voice 1-847-632-5278
> 1501 West Shure Drive, Arlington Hgts. IL 60004
> Public: TIPHON & Other Stds - http://people.itu.int/~emartine/
> Private:TIPHON & Other Stds - http://www.cig.mot.com/~martinze/
>



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