DNS Servers

[Michael Butash]

One thing to keep in mind is the dns lookup on a host is part of the 
transactional process, and inclusive of total delay.

I've seen everything from crappy/slow dns servers causing application 
latency across clusters to broken dns records causing a good 10second 
delay in responding to clients due to dns.  That is part of the reason 
developers will hard code things I've found, working around bad 
infrastructure, sometimes even the dns server's at fault.

Using remote dns (not local lan), consider that takes you from 
microseconds of latency to potentially hundreds of milliseconds remote.  
This is another reason to have local caching servers, or even at times 
local to the hosts as well with something like dnsmasq.  When dealing 
with applications that make dns queries as part of their logic tend to 
dislike remote resources.  With distributed applications and/or latency 
sensitive apps, can cause real performance issues.

Another thing - consider the cost of the dns traffic in bandwidth 
hosting it somewhere.  Watching things like netflow at local dns shop 
was interesting to see just how much dns traffic really does get 
generated, both from servers, clients, and everyone else in between 
local lan or internet.  Even running dns services for a popular domain 
on a dedicated hosting bandwidth allowance, I've seen blow out usage 
thresholds, just in overhead of udp/53 traffic @~64bytes or smaller 
packets.  Probably a poor application too, seen .net code go crazy 
spewing dns requests at crippling rates of requests when not explicitly 
disabling lookups as part of a socket response method.

Side note:

I never realized dnsmasq is as versatile as it is, but using it with my 
little ddwrt box, it does nice things with automagically mapping dhcp to 
forward/reverse dns records with a little config grease.  It's been good 
enough that I retired my bind servers for a more compact/embedded 
solution just on the router itself.  Might be worth looking into.

-mb


On 10/05/2015 12:35 PM, Keith Smith wrote:
>
> Thank you Stephen and Michael!!
>
> Sense I am running a server connected to Cox, is there any advantage 
> of using Cox's DNS servers?
>
> Thanks!!
>
> Keith
>