[dns-operations] Quick anycast primer
Patrick W. Gilmore
patrick at ianai.net
Fri Jul 14 19:23:05 UTC 2006
On Jul 14, 2006, at 3:16 PM, Igor Gashinsky wrote:
> :: For instance, you are a very large provider who spans the
> globe. You
> :: see several instances of an anycast NS called XYZ.ns.
> :: You are personally sitting in Washington DC. Your network peers
> :: providers announcing XYZ.ns in DC, London, NYC, SJC, Tokyo,
> etc. But
> :: it turns out the guy in Tokyo has the lowest IP address, and
> :: therefore won the tie-breaker since the AS_Path Length was the same
> :: to all the instances.
> Uhm, what gear do you use that doesn't do "Closest IGP metric to BGP
> next-hop" before "Lowest RID" during the best-path selection?
> your topology may be different then mine, and if you send different
> MEDs that would cause a simmilar scenario to the one you mentioned,
> then it was *your* decision to do so.. As I said, YMMV, but it works
> rather well for me (and a few million of my users)...
You aren't the first person to ask.
I used the example above because I saw it in real life. (At least
one other on this list can verify.)
Why the network routed the way it did is a good question. It
certainly was not a 'broken' network in the sense that every packet
got where it was going.
Point is, even if you have good connectivity, anycast can still do
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