EDNS request problem on TTL=0 data

[Paul Wouters]

On Tue, 28 Jun 2011, Cathy Almond wrote:

> BIND does take notice of this and it's something we're looking at to
> make better in future releases.  But at the moment it's not foolproof
> and its effectiveness is dependent on circumstances.
>
> There is short term caching of learned 'we don't support EDNS' servers.
> But reaching the point of being able to process and cache them is
> dependent on how many servers we're dealing with for a zone that we're
> querying and also how far down the 'trail' of handling a client query we
> happen to be.  If the client query times out before BIND has finished
> trying and timing out, then it doesn't get to cache what it was in the
> process of learning.

This problem was the reverse. Thousands of clients were asking it, and the
backlog only increased over time because 3 out of 4 seconds the forwarder
was unavailable due to DO packets getting dropped.

Paul