Services@ Servers@ RFC 1035 (in HTML)
DNS Breakout box This allows you to see the exact binary query and response from any DNS server
Reverse DNS ...in-addr.arpa
All Single Letter domains in com, net, org are owned (reserved) by ICANN except for a few such as X.com, Z.com, etc which was registered before ICANN began blocking single-character domain registrations.
If you add two address records for www.myorg.com to your main name server, it rotates the order that these records appear in the DNS response message with each successive reply. (Round Robin was added to BIND at about version 4.9, so your SCO box probably has a Round Robin-capable name server.) You don't need to do anything to enable it--it happens whenever there are multiple records associated with the same name. The problem with Round Robin is that when one of your web servers goes down, the name server still gives out its record, so 50% of the people will choose the dead web server in your case.
The closest thing I've seen is to have your primary web server also act as a DNS server with records that point your domain to the same server. Then setup a secondary server with a service or what ever which points your domain to your backup server. Now, your registrar needs to send name server requests to your primary server and to the secondary server with a lower priority. Not all registrars will do that. The idea is that if a user hits your registrar (or a DNS server that is caching that info) and then tries to resolve your domain buy contacting the DNS server on your primary machine, it will timeout and then go back and try the other one. Note that this does NOT work well at all. It only works in some cases.
Would be much better to have a DNS server (or two) that actually check your servers and switch between them as needed. They would also have to set TTL very low values so that users who are sent to a server that was working will come back after your DNS switchs to a backup and get the other IP again.
http://www.metainfo.com/products/metaip/loadbalancer.htm has a product that can do true load balanceing on NT servers
http://www.acmebw.com/askmrdns/00044.htm O'Reilly "DNS and BIND" book. How to set up a name server
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