about RTT.

[Barry Margolin]

In article <000f01bf24d5$a5428fa0$1e747ca4 at dacom.net>,
HeePok Lee  <wind at bora.net> wrote:
>Hi! all
>I heard about RTT(Round Trip Time) on DNS.
>But I don't know what it is exactly.
>Could you explain what it is?

It's how long a nameserver took to respond to a query.

>And if we have two name servers in America(america.nameserver.com) and in
>Asia(asia.nameserver.com)
>"Cache name server in Asia can always resolve to asia.nameserver.com about
>www.nameserver.com and
>cache name server in America can always resolve to america.nameserver.com
>about www.nameserver.com"
>I heard that it is right cause RTT.
>Is it right?

Not always.  Every time a nameserver is used, its RTT is bumped up a
little.  Eventually its RTT will become larger than the other server's RTT,
so the client will try the other one.  This is done so that a server that's
just temporarily slow will be tried again later, get get an updated RTT.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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