[dns-operations] Multiple NS records vs multiple A records per NS

Ask Bjørn Hansen ask at develooper.com
Tue Mar 22 19:29:55 UTC 2011

Hi everyone,

'pool.ntp.org' is using a bit of custom software to load balance between 2000 NTP servers (and do some geographical "nearby server" stuff).

It's delegated via {a,b,c,d,e,f,g,h,i}.ntpns.org -- and those 9 names then go to about 15-18 servers via anycast (a.ntpns.org) and unicast (the rest).

I've been experimenting with having multiple A records on some of the x.ntpns.org names; the idea is to make it easier to add more unicast nodes and to save a lookup on x.ntpns.org.   In the limited analysis I've done on the query rates, it seems to make basically no difference if an IP address has a NS record "for itself" or is sharing it across multiple A records.

With this in mind then I'm thinking of changing the setup so we just have a.ntpns.org to d.ntpns.org; with a being the anycast address and b, c and d having 3-5 IPs per name.   Does anyone see any downsides to that?

 - ask

Ask Bjørn Hansen, http://askask.com/

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