Guen Moukile wrote:
> Can it be done so that users in Singapore would automatically
> connect to the server in Singapore and users in US would reach
> the server is US?
There are three ways of doing this:
1) Use a third-party product that attempts this feature
UltraDNS offers this as a service. There are other "3-DNS" systems
you can purchase for yourself (Cisco, Akamai and F5 all have products).
2) You can write or hack your own DNS software
Not sure on a good starting point for this.
3) Poor man's 3DNS:
Have each of your web servers also be authoritative DNS servers, with each
returning only its own IP address. A DNS client queries all servers at the same
time, generally the nearest server will answer first. This also has the benefit
if that if a server is down, your DNS will no longer be directing clients to it.
Also, important things to note:
Time To Live (TTL):
Because of DNS caching, balancing and fault tolerance are best effort, the
system cannot be 100%. Using a really low TTL will cause additional load on your
servers, and actually cause outages if there becomes enough server or network
latency that DNS queries time-out. Many DNS servers will not respect your TTLs,
and may cache the address of a server that is later down much longer than you
expected.
Nearest Server versus Geography:
The Nearest server on the Internet very often not the nearest server
geographically. Many countries have competing ISPs that are not well
interconnected (e.g. Australia), and traffic between these ISPs will may transit
an international peering point (e.g. MAE West, MAE East, etc).
Abel wrote:
> This can easily be realized within bind.
> All you need is some knowledge of bind and access to it's conf.
> Also it is part of "normal" routing, IF the bind conf is setup properly,
> if named files are correct it will automatically connect people to the
> "shortest" route.
This is news to me. It's certainly not possible with BIND 4.x. Perhaps
this is a new feature of BIND 8/9? Can you post more details?
Adam
