Subject: [MOBILE-IP] a question about Mobile Ip and fast handoff

From: Roberto Winkler <[email-masked]>
Date: Thu, 27 Jul 2000 16:35:53 +0200

hello,

I don't know how much stupid is my question, I guess I'll be able to rank
it from the answers I'll get.....

Given that Mobile IP is considered to preserve TCP-oriented sessions from
the effects of mobility and given that real time communications will
(mostly, only ? I don't know) be RTP-oriented, what's the reason for the
large interest around fast handoffs enhancements to Mobile IP, where
seamless/lossless handoff should instead be pursued (and I believe that
solutions to the fast and seamless issues are different) ?
Put in another form, why worry about limited scope signaling (e.g. for
registration), for communications which are presumably not bound to be
damaged by some transient extra delay ? Isn't enough to run Mobile Ip (may
be with Routing Optimization) and take advantage of TCP retransmission ?
What strikes me is that I haven't met many proposals for fast handoff
support in RTP-oriented communications, I think that HMMP is the only one I
remember of, whereas I would say that this is the case where smart ideas
should be developed.....

My concern is instead not related to the micro-mobility control (e.g.
Cellular IP, HAWAII and TeleMIP).

Thanks for any hint....

Roberto Winkler
Senior Researcher
Fondazione Ugo Bordoni
Via B. Castiglione, 59
00142 Rome Italy

tel +39 0654803411
fax. +39 0654804404
e-mail [email-masked]

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From: "[email-masked]" <[email-masked]>
Date: Thu, 27 Jul 2000 07:39:15 -0700

> remember of, whereas I would say that this is the case where smart ideas

Actually, I believe that the pro-active Foreign Agent I-D does in fact address
RTP (or real time) traffic. The idea is to provide the data to the mobile as
it enters a new cell, *before* the registration occurs. This will guarantee
the least amount of packet drops.

PatC

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From: "Charles E. Perkins" <[email-masked]>
Date: Thu, 27 Jul 2000 07:50:34 -0700

Hello Roberto,

Answering your question could take megabytes, but I hope a simpler
answer will be at least somewhat useful.

The main point is simplicity.  Mobile IP is one of the simplest
approaches, and even Route Optimization is pretty simple in
terms of control structures.

Smooth handover is to a certain extent independent of Mobile IP.
The point is that higher speed requires maintaining more context
about the mobile node for various reasons, and pushing that state
around is the task for various smooth handover mechanisms.

If you don't have Mobile IP, then you have more state in other
places to substitute (typically poorly) for Mobile IP, and thus
smooth handover is harder.  You can put that state at layer 2
(more complicated! and specific to the medium), at the transport
layer (a reasonable approach as long as you only care about that
transport layer), or at the application (ditto, as long as you only
care about that application, and performance is not an issue).

As always, the devil is in the details.  The details are just
easier at the network layer.

Regards,
Charlie P.

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From: "M. Scott Corson" <[email-masked]>
Date: Thu, 27 Jul 2000 13:51:49 -0400

>easier at the network layer.
 ^^^^^^
 and more general ;-)

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From: Roberto Winkler <[email-masked]>
Date: Fri, 28 Jul 2000 10:21:12 +0200

Hello again,

>easier at the network layer.

I understand Charlie's position (and mostly agree with it) that operating
at the network layer is better, but I'm not sure I've understood what does
Charlie means with this sentence.

More, something I've not found in the replies I've got so far: can you
confirm me that Mobile IP (and related enhancements) are ok in RTP-oriented
communications, altough they've been devised for TCP ?

Thanks again

Roberto

Roberto Winkler
Senior Researcher
Fondazione Ugo Bordoni
Via B. Castiglione, 59
00142 Rome Italy

tel +39 0654803411
fax. +39 0654804404
e-mail [email-masked]