Google public DNS versus my local one

S

snobee

Expert Member
Joined
Sep 26, 2003
Messages
1,002
Hi there,

We have our own main DNS server that all users on the network utilise for local and off site resolving. Currently it points to our leased line local ISP's Cape Town DNS server for off site resolving.

Someone mentioned I should change to google's public dns 8.8.8.8/8.8.4.4. Now, I was curious what people thought about this? Do you think it is better for my DNS server to make a request to Google and have their wealth of cached records, versus my server making a request to the local Cape Town server?
If using Google, my DNS server makes a request, and it would have to go "all the way" to a google international server first, but once there, it should be quicker to retrieve records. While, if my server makes a request to my local CT server, the initial hops are shorter, but that server would probably have to make many more requests to other high level servers than the Google one.
Now, I realise these times between the two options could be milliseconds, but I am just wondering if my reasoning is accurate, and would it really matter which one I use? Any words of wisdom?
 
s0lar

s0lar

Executive Member
Joined
Sep 22, 2009
Messages
5,234
I put this post in the MyBB Linux thread, I hope Mr.Alston doesn't mind me using his post but its describes the issues better than I could.


Hi All,

It has come to my attention after the last Ubuntu release that a fair
number of people are using international DNS servers as their resolvers,
and as a result were getting redirected to the London instance of
mirror.ac.za and using their international bandwidth for local
downloads.

With this in mind, I figured it would be a good idea to put some reasons
down why it's a REALLY bad idea to use international resolvers from .za.

These are a few of them:

a.) Anything that has an anycast instance inside .za and internationally
will go local when resolved off a South African DNS server and
international when its not (mirror.ac.za style)
b.) I.S/SAIX/Others run national Akamai Servers, that serve a TON of
content for various websites, use an international DNS server and you
are going to go to the much slower (and more expensive in terms of
bandwidth) instances
c.) Various other content companies do geographic redirection to their
content to redirect you to the closest (and hopefully least latent
node), using a DNS server internationally completely destroys this

If you are using international DNS servers, if you haven't found it
already, you will soon find that it has a significant performance impact
on a lot of content, and you WILL end up using more international
bandwidth when you don't hit local nodes for various content that is
hosted in South Africa.

If you are using mirror.ac.za and any of it resolves to a 196.32
address, you are using an international dns server, if you are using a
national DNS server it will resolve to a 155.232. address.

Thanks

Andrew Alston
TENET - Chief Technology Officer
 
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