DNS service provider

Zerigo 的 GeoDNS 服務，可以根據訪客來自的國家而對應到接近訪客所在區域的 Server IP address

What is GeoDNS?
If you have servers in multiple locations, GeoDNS provides a way to direct users to the closest server.
Other names for GeoDNS include geolocation load balancing, geolocation-aware DNS, and GSLB (global server load balancing).

Why does this matter?

Consider this example: you have one server in Europe and another in North America. GeoDNS allows you to transparently direct European visitors to your European server and North American visitors to your North American server. Visitors from other continents can be sent to a specific server too, or can be split between the two.
The closest server is almost always going to be the fastest server due to lower network latency. GeoDNS means your visitors get to your site faster.
Better yet, your visitors only ever see “www.example.com”—no funky redirects or weird looking subdomains.

http://jnlin.org/2011/04/21/486/
http://www.zerigo.com/news/launch-of-geodns-geolocation-load-balancing
http://www.zerigo.com/

DNS Made Easy 有 DNS Failover 的服務
http://www.dnsmadeeasy.com/