DNS load balancing: UDP or TCP ?
nicolas at ncartron.org
Tue Feb 19 19:12:37 UTC 2019
On 19-Feb-2019 20:00 CET, <josh.kuo at gmail.com> wrote:
> Agree with Tony on TCP not going to be tried. Have you looked at using
> anycast? It is not true load balancing but it allows you to stand up
> multiple DNS servers that “shares” a single IP address.
or just use a software load-balancer which has been designed to deal
specifically with DNS, i.e. dnsdist - as mentioned by Tony already :)
> On Wed, Feb 20, 2019 at 12:25 AM Tony Finch <dot at dotat.at> wrote:
> > Roberto Carna <robertocarna36 at gmail.com> wrote:
> > > Dear, I have to balance two DNS servers for a special reason.
> > https://www.powerdns.com/dnsdist.html
> > > The DNS clients are a mix of Windows, Cisco and Linux machines, so I
> > > think they ask for a FQDN using UDP and after that -if there is no
> > > response-, they ask the same FQDN using TCP, and so the load balancing
> > > will be succesful.
> > No, fallback to TCP relies on receiving a truncated UDP response. You
> > never want a DNS client to be waiting around for a response that will
> > not arrive.
> > Tony.
> > --
> > f.anthony.n.finch <dot at dotat.at> http://dotat.at/
> > Rockall, Malin: Southeast veering southwest 6 to gale 8, occasionally 5
> > later.
> > Rough or very rough. Rain. Moderate or poor.
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