Evaluating Tier 1 Internet providers
Richard A Steenbergen
ras at e-gerbil.net
Fri Aug 30 03:46:48 UTC 2013
On Thu, Aug 29, 2013 at 08:25:41PM -0700, Luke S. Crawford wrote:
> I have no idea how to solve this sort of problem automatically.
> Ideally, if someone has a congested or down link, I'd prefer that they
> not announce routes to that part of the internet, as I do have a
> backup, but that isn't how it works.
BGP best path routing decisions are made by completely irrelevent
criteria like AS-PATH lengths and lower router-id's, and are completely
blind to things that actualy matter like latency, capacity, packet loss,
etc. Fundamentally it's impossible to fix automatically with the current
routing protocols, and at best the protocol extensions like BGP AIGP
(which could help at least convey some of the data, like the "oh crap I
just got rerouted to a different exit with much higher latency"
situation you mentioned) are still a long way from being practically
usable. At best you can aim your default/tie breaks towards networks you
have "more faith in", but that doesn't mean much in practice. :)
Richard A Steenbergen <ras at e-gerbil.net> http://www.e-gerbil.net/ras
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