how to verify Pipelined TCP and DNSCOOKIE

Ray Bellis ray at
Tue Sep 4 14:40:23 UTC 2018

On 04/09/2018 15:13, Tony Finch wrote:

> `mdig` comes with BIND and does multiple concurrent queries, so you can
> check pipelining behaviour like this:
> ...
> A good selection of sites near and far should nicely demonstrate
> out-of-order replies. If you don't flush the cache first then you'll get
> the answers in an effectively random order.

Technically, pipelining is not the same thing as "out of order replies",
although the former is required for the latter to work.

Pipelining just means that you can submit multiple queries over the same
socket without having to wait for any answers at all, and without the
server flushing its input queue.

AFAIK BIND was always capable of this - the new bit is that BIND will
consume the queries and start processing them (and send the responses
back in whatever order they become available) rather than processing
them strictly in order with each query and response proceeding in
lock-step mode.

This is a distinction that I still have to explain to my RFC 7766
co-authors on occasion :)

kind regards,


More information about the bind-users mailing list