request drops in BIND?

[Paul Vixie]

> But the problem here is, "what level of bulk requests that BIND starts
> to not respond to queries either because of UDP stack overflow or
> BIND's mistake?"

there is no level of bulk requests at which BIND8 will intentionally drop
requests.  we drop requests only if we spend too much time (more than 3
seconds) reloading a zone or performing some other long synchronous
operation.  this is because after 3 seconds, the queries in the kernel
socket buffer have likely been retransmitted by their clients, or have
been tried on other servers, and a reply by us would only cause client
kernels to generate ICMP-portunreach (because the resolver has moved on.)

> Actually I tested sending 10000 requests/second with an equal
> interval. (1 request/100 us).  BIND could handle about 2000
> requests/second, while my UDP PING answered all perfectly.  All the
> test I did is to do just one local domain name lookup.

can i know the operating system, CPU, and memory bandwidth which
generated this result?  those numbers are lower than my results on a
1GHz FreeBSD i386-style box with 400MByte/sec memory read bandwidth (as
measured by lmbench.)

> P.S. I still believe BIND should increase the UDP buffer size for port 53.
>        That will ease the situation a lot.

can you patch it to do so and tell us the results?  i think that it will
change the granularity of your packet loss but not the total percentage.
note that we chose 32K because that was a local maximum here.  if it's
possible to set it even higher then we're willing to consider a patch.