I believe every dns domain is required to have two servers that will serve
up name->address mappings for that domain (for availability). I'd guess
there are about as many dns servers as web servers (O(1M)?).
> How crackpot of an idea is using DNS responses to test loss rates?
Assuming most dns servers are configured to allow TCP connections (i have
no idea; Amit?), it doesn't sound too outrageously crazy 2 me; presumably
it's a lot like using HTTP or echo services to get big packets sent at
yourself.
But with any of these 3 services, it does seem difficult to guarantee the
"ack parity" that sting depends on. The problem, i think, is that with
these request-response apps layered on top of TCP, all of the sudden you
have to worry about several kinds of packets that the server spits at you:
acks for your requests, the responses from the server, and the
*retransmitted* responses from the server. Depending on the server's OS,
the server application, and the timing of your requests, each packet you
send may result in 1 or 2 packets back from the server. And if a response
packet gets lost, the server will usually try to retransmit it. Blech. No
parity there. Still, i'm not saying this problem can't be overcome. I've
learned it's a bad idea to bet against Stefan's ability to find TCP hacks
to solve any given problem... ;-)
neal