Resilience - How many BGP providers

Richard A Steenbergen ras at e-gerbil.net
Thu Nov 12 13:44:41 CST 2009


On Wed, Nov 11, 2009 at 11:18:20AM -0800, Steve Gibbard wrote:
> If you have three components, the chances of all three being broken at
> once are even less than the chances of two of them being broken at
> once.  With four, you're even safer, and so on and so forth.  But once
> you get beyond two, you hit a point of diminishing returns pretty
> quickly.

Not only that, but you have to ask yourself what are the chances that
all these extra components will become extra points of failure and
actually increase the likelihood of something going wrong. I know a lot
of folks who have gotten themselves into a lot of trouble buying transit
from everyone they can possibly buy from, thinking it will make their
network more reliable. In most cases all it does is make their network
more unstable. The more transit paths you have out there, the more
likely you are to have something flap and wipe you out w/flap dampening,
and the more likely you are to see any single event cause a massive
amount of churn. I've seen people with 8 transit providers appear to
others on the internet as though they flapped 100+ times over a single
session flap, because of all the churn as the network reconverges. More
transit providers also means more 95th calculations, and thus a higher
bill, but that is another story for another day. :)

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)




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