Resolving Internet names: Actually call root servers?

Jim Reid jim at rfc1035.com
Sun Sep 3 19:17:03 UTC 2000


>>>>> "Frederic" == Frederic Faure <ffaure at bigSPAMGAMOUTAKUSANfoot.com> writes:

    Frederic> Thx also to Mark, although I obviously know that "."
    Frederic> servers do delegate to lower-level servers to actually
    Frederic> resolve a host name. I asked because it seems hard to
    Frederic> believe that those 10-so servers sitting in name.ca were
    Frederic> actually queried every day by millions of DNS servers
    Frederic> whenever they need to resolve an Internet address that
    Frederic> happens not to be in the local cache.

This is pretty much what does happen, though not quite in the way you
envisage. The first time a name server is asked for a name in some
top-level domain (TLD), it will query a root server and get a referral
for that TLD. The details of that referral - NS and A records - are
cached. Subsequent lookups of names in that TLD will go to one of the
name servers for that TLD. Once those cached NS and A records for .com
(say) expire, your server will consult the root name servers to get
a fresh referral to the .com name servers.

The internet's root servers are very busy and typically handle 1000
queries a second or more. f.root-servers.net is probably the world's
busiest name server. It gets ~260 million queries a day: 3000 queries
per second. [See http://www.isc.org/services/public/F-root-server.html.]
An overwhelming majority of those lookups are from spectacularly badly
misconfigured name servers (and resolvers!!!) that look up
non-existent names. BTW RFC2870 - Root Name Server Operational
Requirements - gives some idea of what's involved in running such a
server. A lot of the advice in that RFC is relevant to any important
name server.



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