Yet another Quadruple DNS?

Stephane Bortzmeyer bortzmeyer at nic.fr
Tue Apr 3 09:45:05 UTC 2018


On Sun, Apr 01, 2018 at 09:22:10AM -0700,
 Stephen Satchell <list at satchell.net> wrote 
 a message of 39 lines which said:

> Recursive lookups take bandwidth and wall time.  The closer you can
> get your recursive DNS server to the core of the internet, the
> faster the lookups.

I think the exact opposite is true: many DNS requests hit the cache,
so the important factor is the latency between the end user and the
cache. So, local resolvers win.

> This is particularly true of mobile and satellite.

Yes, because they have awful latency, it is important to have a local
resolver.

> (I wonder if the Internet Systems Consortium has considered adding a
> cache-hit counter, or even a very coarse heat map (say, four 16-bit counters
> cycled every five minutes), to DNS entries, to figure out the best ones to
> drop?  It would increase the complexity of BIND, but the benefit for a BIND
> server serving a largish customer population could be significant.

Making the largest and richest services even faster and so increase
centralisation? It does not strike me as a good strategy.

> I've not personally measured the number of times a look-up could be
> satisfied from a cache in a production environment;

For instance, at my home:

% cache.stats()
[hit] => 276089296
[delete] => 5
[miss] => 423661208
[insert] => 18850452

> The main reason for *not* implementing recursion exclusively in CPE
> is that a recursive lookup is a complex operation, and I have my
> doubts if BIND or equivalent could be maintained properly in, say, a
> wireless access point (router) -- how would you update a hints
> table?

There is nothing DNS-specific here: routers/CPE with automatic updates
exist for several years (I use the Turris Omnia
<https://omnia.turris.cz/en/>). The hints file is the *last* problem:
most IP addresses of the root name servers didn't change for more than
ten years.




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