DNS load balancing: UDP or TCP ?

[Kevin Darcy]

If you go with Anycast via BGP, make sure your network infrastructure has
"multipath" enabled, otherwise the traffic will be skewed to one node or
the other.
https://tools.ietf.org/id/draft-lapukhov-bgp-ecmp-considerations-01.html is
one source which summarizes some of the literature and standards on the
subject.


                                                - Kevin

On Tue, Feb 19, 2019 at 2:01 PM Josh Kuo <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.
>
> 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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