Geographic routing hack

Tue Aug 3 02:04:22 UTC 1999

Note that the particular case in question could also be
an implementation of Cisco's DistributedDirector product,
which responds to DNS requests with the closest server to the
querying machine.

/cah

On Mon, Aug 02, 1999 at 02:59:05PM -0600, Alec H. Peterson wrote:
==>
==>Martin Cooper wrote:
==>> 
==>> Some weeks ago I noticed that 167.216.128.247/32
==>> (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 - ahp at hilander.com
==>Staff Scientist
==>CenterGate Research Group - http://www.centergate.com
==>"Technology so advanced, even _we_ don't understand it!"