[dns-operations] Anycast vs. unicast NS

David Ulevitch david at opendns.com
Thu Mar 17 17:55:28 UTC 2011

On Mar 17, 2011, at 9:47 AM, Jaroslav Benkovský wrote:
> We do not see significant amount of queries to the unicast servers, on
> the other hand our experiments suggest that unicast servers have better
> chance to be reachable from networks with problematic routing.

That has more to do with prefix size than anycast.  If you are unicasting or anycasting from a /24 that has no covering prefix, there are networks on the Internet who may not be able to reach you (e.g. SwissCom when reaching ARIN assigned PI space).  So for OpenDNS' anycast network, we also pin down a /21 that is always reachable through at least one site.

As others have pointed out, if "problematic routing" means folks doing per-packet load balancing across different AS exit points, that's pathological as Joe puts it, and they will have a lot of other problems.


More information about the dns-operations mailing list