From:  Patrick McManus <>
Date:  07 Dec 2014 22:38:36 Hong Kong Time

Re: Reducing DNS latency


On Sat, Dec 6, 2014 at 7:21 PM, Christopher Barry <> wrote:

> My strong opinion, and indeed it is the understood expectation of anyone
> using any application that requires name resolution, is that all
> applications always strictly obey the local resolver configuration of
> the host running the application. Period.

I'm going to push back against this notion that operating system services
must always take priority.

For instance, windows provides a trust root list that firefox ignores in
favor of its own. That's a design choice.

There are several reasons we might do things like that - performance,
security, and the ability to effect legacy configurations for example.
There are also costs in terms of administrative awkwardness, surprises, and
incompatibilities. Its not to be undertaken lightly.

It would be wrong to interpret this mail as supporting the algorithm being
discussed in this thread (I'm basically open minded on the topic), I'm just
saying its plausible to discuss.

The much larger problem, to me, is that use of a public dns adds another
party to your transaction: {client, origin, isp, public-dns} .. its
conceivable such an algorithm would boost performance using only multiple
isp servers, but there is no evidence to show that at this point and
honestly thin evidence overall. So its the kind of thing that bears more

regardless of possible performance benefit. If this is what FF is doing
> now,

Just to be clear - this thread is discussing the results of a small
academic experiment not of general Firefox behavior. I appreciate the
authors bringing it here to discuss - let's keep it a welcoming environment
for exploration.

-Patrick (wearing module owner hat).