load-balancing in DNS using two A records

Mark Andrews marka at isc.org
Wed Dec 21 10:35:23 UTC 2011

In message <20111221083337.GB5238 at fantomas.sk>, Matus UHLAR - fantomas writes:
> >In message <20111220182222.GA3085 at fantomas.sk>, Matus UHLAR - fantomas write
> s:
> >> Long time ago when we were trying to have multiple web servers for
> >> redundancy and balancing, we have found that multiple IP's is not a
> >> good solution (parts of web pages didn't load). We selected L3
> >> switches then...
> On 21.12.11 09:26, Mark Andrews wrote:
> >Which is really the result of badly designed clients.  Clients are getting
> >better with address affinity and fast failover on unreachable servers.
> It's been long time ago (~10 years). And even if they did failover, 30s 
> (tcp connection timeout) delays are very ugly when loading a web page.

Indeed.  150-250ms [1] is a more realistic timeout for starting a second
connection attempt.  You use the connection which completes first and
close the others if they complete.


[1] http://tools.ietf.org/html/draft-ietf-v6ops-happy-eyeballs-07
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org

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