Age Old DNS Round-Robin Question

[CaseyBlackburn]

There are always multiple views on this and I'm trying to get the best setup for my ideal use.

I want to ensure I have my name servers for web hosting failover the quickest way on a DNS resolve. I currently am running 16 named servers distributed across the US.

Which will failover the quickest to get the A record for the domain:

Domain: test.com
A record: 1.1.1.1
Name Servers:
NS1.HOST.COM
NS2.HOST.COM
NS3.HOST.COM
NS4.HOST.COM

Domain: host.com
A NS1.HOST.COM 1.1.1.1
A NS1.HOST.COM 1.1.1.2
A NS1.HOST.COM 1.1.1.3
.....
A NS2.HOST.COM 1.1.2.1
A NS2.HOST.COM 1.1.2.2
...
Etc


Or

Domain: test.com
A record: 1.1.1.1
Name Servers:
NS1.HOST.COM
NS2.HOST.COM
NS3.HOST.COM
NS4.HOST.COM
NS5.HOST.COM
NS6.HOST.COM
NS7.HOST.COM
Etc....

Domain: host.com
A NS1.HOST.COM 1.1.1.1
A NS2.HOST.COM 1.1.1.2
A NS3.HOST.COM 1.1.1.3
A NS4.HOST.COM 1.1.2.1
A NS5.HOST.COM 1.1.2.2
A NS6.HOST.COM 1.1.2.3
Etc

Any responses would be appreciated, especially relating to OS specific differences in resolv.

 

[mwarps]

Trying to decipher the meaning in your post is giving me a headache.
You want to have round robin nameservers? Please stop.
You can't have round robin nameservers. (EDIT, oh wait, yes you can, but it's dumb and slow)



If you're looking for speed, using a roundrobin scheme is not the way to do it. Timeouts and downtime (if the server stays down hard) will last anywhere from 2 seconds (normal retry period on most OSes) to 2 days (standard glue timeout) and it's very difficult to predict how long it lasts, since the public is free to use broken resolvers. Most high-speed internet users have an extremely unfavorable view of sites that take more than 750-1000ms to load, never mind a 2,000 millisecond DNS timeout (assuming only one of the 16 is down) plus load time.

Never mind that geographic unicast is ancient, slow, and doesn't work.

You should be using Anycasted DNS. Anycast takes the 4 nameservers (domains are usually delegated to 2-4 nameservers), and makes them available at the same 4 IP addresses at multiple locations across the planet.

Managed DNS providers have been doing Anycast for years. Here's the best ones (listed by fastest first):

http://dyn.com/dns/dynect-managed-dns-lite/

http://www.dnsmadeeasy.com/managed-dns-hosting/

http://www.neustar.biz/enterprise/dns-services/external-dns-packages#.Udg5gflJN0M

 

[CaseyBlackburn]

Thanks for the reply. Basically I confusingly was just trying to reference something simple in which the longer failovers most DNS resolving clients were on trying A records or NS records and the typical timeouts on them. I'm working on design a special purpose Anycast DNS system. Just was trying to simplify a question and made it more confusing in the long run.

Thanks, my initial assumptions were correct in the order of how DNS tries entries.

 

[shade91]

Self-hosted unicast DNS? What is this? The 1990's?

 

[TCM]

If round-robin is evil, why have more than one DNS server anycasted in the first place?

 

[mwarps]

If round-robin is evil, why have more than one DNS server anycasted in the first place?

Never said it was evil. It's just slow and dumb.

To answer your question, advertisement diversity (which can have as much or as little meaning as you'd like), throw in some RTTM banding, and of course RFC.