Hi Everyone:

I fully agree with Roelands Marc's comments (along with Roberto Winkler and Simon Binar) that Edgar Martinez's proposal is "mixing all kinds of mobility related functionality in a single, strongly coupled, do-it-all-in-H.323 layer, involving radio access up to H.323 application layer."

H.323 mobility problems needs to be addressed in H.323 layer. That is, H.323 is independent of the underlying transport network (e.g., IP, ATM, MAC, radio-access, wireless LAN, etc.). However, H.323 solutions (fixed or mobile) can be implemented over any packet-based network (PBN). In this context , we also produced a terms of reference document (TD-34) in the last SG!6 Q.13 Berlin meeting.

Now Roelands's comments also clarify more how H.323 mobility problems need to be addressed. I support almost all the points mentioned by Roelands. Please also see my comments enclosed below.

Best regards, Radhika R. Roy AT&T + 1 732 370 2542 rrroy@att.com

PS: Once the general mobility problems are solved in the H.323 layer, a specific implementation what Edgar Martinez has proposed in the context of the PSTN-radio-access (e.g., WAU) can be addressed very easily (e.g., wireless-PSTN-[WAU]-H.323 [ e.g., IP Network] Mobility).

-----Original Message----- From: Roelands Marc [SMTP:Marc.Roelands@SIEMENS.ATEA.BE] Sent: Tuesday, September 14, 1999 10:17 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: [Fwd: Re: [Fwd: [Fwd: [Fwd: Re: H.323 mobility first darft]]] ]

Hi all,

I am struggling with some conceptual problems concerning the Annex-H proposal of Edgar Martinez, feeling that this has some commonality with the remarks of Roberto Winkler and Simon Binar on it. IMHO, the proposed architecture, and especially the WAU and the GK, are mixing all kinds of mobility related functionality in a single, strongly coupled, do-it-all-in-H.323 layer, involving radio access up to H.323 application layer.

[Roy, Radhika R] I fully agree with Roelands Marc.

Specifically, I have some difficulties with the following:

1. No clear division in terminal and user mobility aspects in the basic

H.323 architecture is taken as a starting point: shouldn't there be specified somewhere in general, in conjunction with the H.323 set of protocols, that IP addresses represent terminals in an IP network, and that users can only be represented by logical names from a directory (i.e. aliases), and whether an "endpoint" is a user or a terminal? If this is decided on, the H.323 registration procedure is just what is needed to have user mobility, by dynamically associating a logical user name with one or multiple terminals upon user request. With terminals identified by IP addresses, terminal mobility would further be strictly a network access problem.

[Roy, Radhika R] Yes, Edgar Martinez's proposal does not separate clearly between the terminal and user mobility. We need to solve problems step-by-step as specified in the terms of reference document (TD-34): 1. Terminal Mobility, 2. User Mobility, and 3. Service Mobility.

2. Annex-H is supposed to handle user and service mobility, so why would

the handover problem, as any other terminal mobility related problem, be handled here instead of independently in Annex-I?

[Roy, Radhika R] Per last SG16 Q.13 Berlin meeting, Annex H will deal with all: 1. Terminal Mobility, 2. User Mobility, and 3. Service Mobility.

3. Mobility is not an issue in H.323 alone, e.g. consider roaming and

handover for a connection-oriented data application, so why should it be handled in H.323 on its own? Or put otherwise, is H.323 support really required on a terminal in order to be able to roam, as a user of some service, or as a terminal accessing a network?

[Roy, Radhika R] H.323 needs to handle roaming and handover in the H.323 layer as well if this is NOT transparent to the H.323 layer. For example, a handover to a "new" connection may cause to release resources to the "old" connection by the GK. The multipoint controller (MC) that has the capability to create new connections while terminating the old one via ad hoc conferencing can be used to provide handover in the H.323 layer (In turn, this may also be coordinated for implementation of the handover in the physical [wireless] layer).

4. Although the proposal pays attention to the identification of several

degrees of locality for roaming and handover, solving all control issues (radio access, IP-networking, etc.) in a single application layer still leads to both resource sub-optimality and complexity. E.g. why should the WAU be aware of anything having to do with (user) mobility management?

[Roy, Radhika R] Yes, we need to solve mobility problems in H.323 layer in a transport independent way (however, specific implementations can be offered at the radio access layer, IP network layer, etc.).

Instead I would propose to use an approach of highly independent layers, following good Internet tradition, and solving the problems as locally as possible (both geographically and architecturally). Here's the layers I think at least should be distinguished:

• MAC level: terminal micro-mobility across radio cells, ethernet

segments, etc. can exist without any consciousness of this at the IP level (e.g. using wireless LAN tunneling techniques);

[Roy, Radhika R] H.323 mobility solutions shall be transparent to the lower transport layers.

• IP network level: terminal macro-mobility across the Internet should be

invisible to higher layers (e.g. by means of Mobile IP v4 or v6 and the improvements suggested for delay-sensitive traffic like RTP streams: Mobile IP HAWAII, or draft-elmalki-mobileip-fast-handoffs-01 to name but a few; note that route optimization is also worked on in this area);

[Roy, Radhika R] Yes, I agree.

• "terminal real-time signaling" application level: the level where

telephony and MM signaling like H.323 can be placed (restricting GW and GK functionality to strictly this level); here Annex-H might define transport for additional parameters and vertical signaling, useful for serving the "user services" application level (below); at this lowest application level packet to circuit switched network boundaries may be crossed (cf. the evolving traditional telephony networks vs. the Internet);

[Roy, Radhika R] Annex H will also specify 'Interworking" between H.323 and non-H.323 (e.g., wireless-PSTN-H.323 [IP]) system. However, in an H.323 system, both GW and GK will be using the H.323 protocol.

• "user services" application level: user and service mobility takes place

here, making use of a network- (and H.323) independent naming system (directories using e.g. DNS, LDAP schemas, etc.) and e.g. back-end services, "behind" or "on top of" one or several GKs for realizing UM, user mobility support for a larger scope than just H.323, smart user assistance, etc..

[Roy, Radhika R] H.323 service mobility needs more careful considerations because H.323 is yet to standardize backend services protocol.

This approach has not only the general advantage that every layer can evolve technically independent of all others, it also has the specific advantage that it realizes true consolidation of mobility for telephony and traditional data applications.

[Roy, Radhika R] TD-09 and TD-34 clearly indicate how H.323 mobility problems need to addressed. Contributions are solicited by SG16.

As a last point, it is not clear to me at which of these levels H.450 would belong. As it is specified now it is on top of H.323, but suppose one would like to adopt a service provision model where a user could subscribe to a telephony-related service , wouldn't it be nice then to be able to offer this across different telephony technologies (a bit like where IN aims at)? A comparison to using a HTTP service control layer (Annex-K) might be interesting here.

[Roy, Radhika R] It is clearly an issue. We need to address this as we go forward.

I cannot imagine that these fundamental issues where not previously discussed in ITU-T SG16 or Tiphon WG7, so if anyone can give me some arguments why an approach as I tried to describe here could not be followed, I would be glad to know about it.

[Roy, Radhika R] All issues were discussed in the last SG16 Berlin meeting. Contributions are solicited (Edger Marinez's proposal is one such contribution. More contributions are expected in this area).

Regards, Marc Roelands Siemens ICN Atea Atealaan 34 B-2200 Herentals Belgium Tel.: +32 14253965 Fax: +32 14222994 E-mail: marc.roelands@siemens.atea.be

-----Original Message----- From: Roberto Winkler [mailto:wnk@FUB.IT] Sent: Tuesday, September 14, 1999 10:34 AM To: TIPHON_WG7@LIST.ETSI.FR Subject: Re: [Fwd: Re: [Fwd: [Fwd: [Fwd: Re: H.323 mobility first darft]]]]

Jin, Edgar,

If I may try to give my 2 cents in this discussion, I think that the problems/weakness of 3GPP considered systems (which Edgar is speaking about) cannot match with the faults identified by Lucent's contribution, which is focused on the unique issue of R99 terminal support in the All IP R00 network. Considering these 3GPP contributions does not help in understanding Edgar's point of view. I have already sent a few e-mails to comment the proposed mobile H.323 architecture and would like to summarize here my view, hoping to get reactions:

• the role and reason for being of WAU is unclear (as TIPHON is focused on

user and service mobility, why worry about the access medium ?)

• the redefinition of several RAS channel messages is confusing (why does

the RAS channel terminates at WAU ?)

• protocol stacks and interface definitions are missing from the picture.

best regards