Re: [Irtf-mobility-charter] IP Mobility Optimizations (Mob Opts) RG charter

"Michael A. Ramalho" <mramalho@cisco.com> Mon, 06 October 2003 19:40 UTC

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Date: Mon, 06 Oct 2003 15:38:43 -0400
To: Rajeev Koodli <rajeev@iprg.nokia.com>, irtf-mobility-charter@irtf.org
From: "Michael A. Ramalho" <mramalho@cisco.com>
Subject: Re: [Irtf-mobility-charter] IP Mobility Optimizations (Mob Opts) RG charter
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Rajeev,

Re: IP Mobility Optimizations (Mob Opts)

I have a question regarding the last paragraph in the "research
group" charter.


>The research group addresses questions of an evolutionary nature,
>making use of the IP Mobility architecture (i.e., Mobile IP and
>handover optimizations such as Fast Handover and Hierarchical Mobile
>IP) developed in the Mobile IP Working Group. In particular, radically
>new architectures (e.g., based on the separation of identity and
>location) are outside the scopeof this group.

Although not explicitly stated, I think the underlying assumption
of the entire group is that TCP is assumed. That is, to maintain
a particular session during mobility (e.g., handoffs between wireless
links in different subnets) that the "IP address of the mobile node
endpoint" must remain the same for the duration of the session.
MIP or routing technology is fundamentally assumed here so that the
mobile node IP address remains the same as far as the other end host is
concerned. This is obvious from the "new route establishment" example
provided in the proposed charter.

If a MN were allowed to change/add/delete a new IP address without
breaking the session - the "new route establishment" in the charter
wording wouldn't need to occur! [Indeed, even neither MIP tunnels nor
routing updates would be required!] Thus another obvious "solution"
is to create another transport layer that doesn't have the rigid "one
IP address forever" constraint built in (as TCP does). Note that if one
had such a transport that a "new [Internet] architecture" would also
not be required (only normal IP forwarding is required). "Handovers"
across disparate wireless networks would also be less of an issue
(you only need to concern yourself with link layer and network layer
re-establishment).

If this group is indeed a "research group", I think other transports
without this constraint could be investigated. Or the group could
explicitly exclude such work.

I'm not against the charter work as described if the group only wants
to consider TCP for legacy reasons. However, this important TCP
constraint should be explicitly stated.

Regards,

Michael Ramalho

Michael A. Ramalho
Office email: mramalho@cisco.com
Personal email: mar42@cornell.edu
Office: +1.941.708.4650
Cell: +1.941.544.2844


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