H.323 Annex I

Roy, Radhika R, ALARC rrroy at ATT.COM
Tue Nov 23 19:55:17 EST 1999

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
*       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

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

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
+1 732 420 1580
rrroy at att.com

More information about the sg16-avd mailing list