Re: HSRP-like virtual DNS services.

BM> [DNS Client libraries] typically allow you to specify multiple
nameservers,
BM> but they often have a relatively long timeout (a few seconds) to switch
BM> over to the backup server. And they go through this timeout for
BM> every query; [...]

Not all DNS Client libraries do that. There is one particular DNS
Client library that, due to an implementation bug (since fixed, but with
the erroneous version still in widespread use), queries the alternate
proxy DNS server first for every subsequent query after it has once
timed out trying to query the preferred proxy DNS server.