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 > [EMAIL PROTECTED] > > [1] A search engine likely can find a PDF copy of this; > I don't have one to hand this minute. > > -- > to unsubscribe send a message to [EMAIL PROTECTED] with the > word 'unsubscribe' in a single line as the message text body. > archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg > -- to unsubscribe send a message to [EMAIL PROTECTED] with the word 'unsubscribe' in a single line as the message text body. archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg
