[24694] in North American Network Operators' Group
Re: Geographic routing hack
daemon@ATHENA.MIT.EDU (Alec H. Peterson)
Mon Aug 2 17:09:23 1999
Date: Mon, 02 Aug 1999 14:59:05 -0600
From: "Alec H. Peterson" <ahp@hilander.com>
To: Martin Cooper <mjc@cooper.org.uk>
Cc: nanog@merit.edu
Errors-To: owner-nanog-outgoing@merit.edu
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@hilander.com
Staff Scientist
CenterGate Research Group - http://www.centergate.com
"Technology so advanced, even _we_ don't understand it!"
