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Re: Geographic routing hack
Martin Cooper wrote: > > Some weeks ago I noticed that 220.127.116.11/32 > (www.digisle.net) appears to reach web servers > located in physically different places broadly > dependent on where you see it from. > > I presume this is done by advertising the same > prefix from border routers which are in seperate > IGP domains or something (confederations maybe?), > but I wonder what people's views on the concept are, > since it could potentially be quite confusing in > certain circumstances (e.g. debugging routing > problems) ? > > Superficially it seems like a 'cool hack' for > geographic content-distribution (which is what > Digital Island do), but up until now I've always > seen this sort of thing done by exploiting NS > record sorting order properties with the kludge > of different A records in the various zonefiles, > and I wondered if doing it with routing policy in > this way is strictly RFC compliant (or for that > matter if anyone cares if it isn't) ? This certainly isn't a new idea, although it is generally considered poor form to do this with stateful protocols (such as TCP), since the 'closest' instance of the address can change mid-session, and thus cause a reset. Several presentations on using this hack in various situations have been made at NANOG. See http://www.hilander.com/nanog11 for one such presentation. Alec -- Alec H. Peterson - [email protected] Staff Scientist CenterGate Research Group - http://www.centergate.com "Technology so advanced, even _we_ don't understand it!"