Re: [RRG] Mobility frequency

[Brian E Carpenter <brian.e.carpenter@gmail.com>]

I think we should also remember Layer 7 mobility. There are many
application suites that recover in one way or another from
a low frequency of Layer 3 disconnects and re-addressing events,
using Layer 7 identities to restore a connection and to maintain
application state. This is so much established practice that it
really gives us license to offer best-effort mobility at Layer 3.
That doesn't mean we shouldn't strive for fast handover etc.,
but ultimately it's the applications' job to survive connectivity
problems.

   Brian

On 2008-02-22 02:37, Randall Atkinson wrote:
> An earlier separate comment by Scott Brim triggered this thought...
> 
> Some in the IETF (historically at least, maybe not now) have wanted
> to have IP mobility work well with many roaming events in 1 minute.
> 
> There is a useful and interesting NATO technical report [1] on IP mobility
> that concludes that current IP mobility schemes don't really work well
> for a device that moves its (layer-3) location more often than once
> every few minutes.  Their conclusion, as I recall, was that when
> considering mobility one ought to be trying to use Layer-2 mobility
> (e.g. radios, satellites) for smaller and high frequency movements
> (e.g. movements on the scale of seconds) and using layer-3 mobility
> much less frequently (e.g. movements on the scale of several minutes
> or longer).
> 
> That NATO report seems pretty sensible to me.  If one considers a
> classical radio LAN, a node typically can move for a while/distance
> before one needs to find and engage with a new uplink base station.
> At least some mobile phone technologies also support the idea of
> L2 mobility (e.g. between individual cells, but within one super-cell)
> where an L3 handoff is only needed/applicable/useful between
> super-cells.
> 
> The question of how much mobility a proposal ought to support,
> if any at all, seems like a good one to ponder.
> 
> Yours,
> 
> Ran
> rja@extremenetworks.com
> 
> [1] A search engine likely can find a PDF copy of this;
> I don't have one to hand this minute.
> 
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