Paul,
I go along with the “optimal number of root name servers”.
Besides, the distribution of root zone file among the servers with a
pleasing latency therefore bears importance.
Truly an interesting topic for the testbed by ZDNS and BII.
Declan Ma
ZDNS Ltd.
> 在 2014年11月28日，下午3:21，Paul Vixie <[email protected]> 写道：
>
>
>
> Davey Song wrote:
>> I try to express the idea: is there any possibility that if we can
>> breaks the rareness of Root servers. The arguments and disputes will
>> cease accordingly. Actually this idea is out of the scope of this draft.
>
> i think there is an interesting research question here: how many root
> name servers is too many, and what are the limitations, and what is the
> optimal number of root name servers?
>
> for example, if 13 is good, would 130 (10X) or 1300 (100X) be better?
> even with 1300 root name servers, the fallback to TCP after TC=1 in a
> priming query (even with EDNS) would only add one extra round trip over
> the three that are required to run a TCP query. since priming queries
> are uncommon, i still don't see why that first round trip is worth avoiding.
>
> RDNS servers who perform round trip measurements to each potential name
> server for each zone cut would have a lot more state to maintain, but
> that state would not be large by today's standards (DNSSEC signatures
> have bloated RDNS memory footprints far more, without concern.)
>
> however, the systemic complexity of all those RDNS servers performing
> all those measurements seems like cause for concern. with 1300 root name
> servers, it would take 1300 referrals for any given RDNS server to learn
> which root name server was closest to it. unless all 1300 of those
> servers are widely anycast, then many of those initial 1300 referrals
> would have suboptimal round trip times. also with that many servers,
> error theory predicts that some number of them will be unreachable,
> causing retries that add to the total number of referral events required
> to locate the closest (by RTT) root server.
>
> if 1300 is obviously too many, why? what's the optimal number of root
> name servers for an RDNS population estimated to be about 40M? does the
> optimal number change when some share of root name servers are widely
> anycasted?
>
> i share these research questions for four reasons.
>
> first, ZDNS and BII are ideally suited to investigate this matter in
> your test bed.
>
> second, there is no evidence at present that "13" is too many or too few
> root servers.
>
> third, this line of thinking is what led to my ICANN ITI proposal
> involving only two root name server identities, each of which being
> massively and hierarchically anycasted.
>
> fourth, because without an answer to these research questions, it's
> impossible to evaluate the cost and complexity tradeoff against
> increased internet resilience from pursuing your "tcp-primingexchange"
> proposal.
>
> --
> Paul Vixie
>
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