[dns-operations] The (very) uneven distribution of DNS root servers on the Internet

Andrew Sullivan ajs at anvilwalrusden.com
Tue May 15 17:03:04 UTC 2012

On Tue, May 15, 2012 at 12:24:35PM -0400, Edward Lewis wrote:
> To me the question is the accuracy of the following statement in the
> article, not the precise numbers themselves:
> "One would imagine that if all things were equal, the distribution
> of root servers should mirror the distribution of Internet users."
> That sentence seems nice on the surface, but I don't think it is
> true.  As another poster notes:

That does seem to go to the heart of the matter.

> neither)?  Perhaps a root server can handle 30M people's needs.

This highlights an important and interesting question, however.  I am
not an advocate of a strong one-boss-to-rule-them-all model of root
zone operations.  On the root-servers.org site, however (which seems
to be the source of at least some of the data pingdom is using), there
isn't anywhere one can find a description of how sites are chosen by
the various operators nor what factors determine provisioning in those

Let me make up an implausiblr scenario to illustrate why this might
matter, and how additional coverage could in principle get worse by
adding more nodes (an issue not clear in the pingdom article).
Suppose that in Viet Nam there is an IX, that most of the ISPs in Viet
Nam have a presence in that IX, and that all the pariticpans in the IX
have free and easy peering policies.  Suppose also that the ISPs in
that IX all have extremely good connections to Singapore and Malaysia.
As a result of all of this, ISPs all have extremely good connectivity
to F, I, and J.  Suppose L puts a node in the Vietnamese IX.  Service
is improved in the sense that RTT on root queries goes down when
they're directed to L.  However, if L accidentally puts an
underprovisioned node in Viet Nam, and it is sometimes overwhelmed,
then service actually gets _worse_: the overwhelmed node sometimes
drops queries or crashes or traffic gets routed elsewhere; in any
case, there is additional latency that results from having to recover
from the overload condition.

This kind of worry (and I want to emphasise I don't share it; I'm just
pointing out that people who like to worry about this sort of thing
have an argument) could be addressed by various server operators
providing outlines of how they select sites, what their provisioning
assumptions are, and so on.



Andrew Sullivan
ajs at anvilwalrusden.com

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