[dns-operations] On server selection algorithms in dns resolvers

[Roy Arends]

When resolvers select a server to query, from a pool of many, does the pool consist of just addresses, a combination of name-server name and address or just name-server names?

To illustrate, assume a delegation for .example with the following records and glue in a fictional root zone.

example. NS a.example.
example. NS b.example.

a.example A 10.0.0.1
a.example A 10.0.0.2
b.example A 10.0.0.2

When the strategy is to select from a pool of addresses or hostnames, then there are two in each case, and if the distribution is equal, each get 50% of queries.
When the strategy is to select from a pool of records, then there are three (the three A records), and address 10.0.0.2 would get 66% and host “a.example" would get 66%, etc.

Thanks!

Roy

PS, I’ve read a few papers on server selection algorithms, but none of them specify ‘server’ as name, address or combination.