[dns-operations] Anycast vs. unicast NS

Gilles Massen gilles.massen at restena.lu
Fri Mar 18 10:33:08 UTC 2011

On 03/18/2011 11:13 AM, Shane Kerr wrote:

> Having a fewer number of entries in your NS RRSET and making those
> highly anycast should result in a better user experience than having
> more unicast servers. This is because resolvers don't have to go through
> as much pain figuring out the best RTT, as the routing system has
> already done that work.

I don't think that's true: routing doesn't care for TTL but for shortest
AS path. Once your packet hits one of the large Tier-1 ASs, all bets are
of as on which anycast node it will end...

> It's magic! And you are probably better off not having unicast at
> all. :)

My view is the exact opposite: I'd always keep at least one unicast node
running: the resolver takes care of not querying it, if it is too slow,
and it should be visible to anyone, even to those with
broken/pathological/paranoid routing.

Should I be worried if you don't trust the resolvers? :)


Fondation RESTENA - DNS-LU
6, rue Coudenhove-Kalergi
L-1359 Luxembourg

More information about the dns-operations mailing list