Domain Name System

DNS servers have a table of domain names with their associated IP address. When clients send a query with a domain name, the server return the associated IP address.

		DNS server data www.msn.com = 209.47.184.43
	What is the IP address for www.msn.com? ÆÆÆÆÆÆÆÆÆÆÆÆÆÆÆ ÅÅÅÅÅÅÅÅÅÅÅÅÅÅÅ              www.msn.com is 209.47.184.43
DNS client		DNS server

DNS allows the authority of name definitions to be distributed to multiple servers by dividing the namespace into zones based on the hierarchy. DNS servers are responsible for resolving DNS queries within their zone.

Name resolution may involve consulting multiple DNS servers each responsible for a different zone, as shown in the following diagram.

				Other	DNS servers
			2nd query		root DNS server
DNS client	Preferred DNS server		3rd query		com DNS server
	Å1st DNS queryÆ
			4th query		msn.com DNS server
			5th query		test.msn.com DNS server

DNS clients and servers cache the results of the name resolution for a time specified on the DNS server.

DNS client resolver		Client-to-server query	Server-to-server query
		Zones ÇÈ	Recursive
Web browser URL:www.msn.com	resolver cache ÅÆ	ÅÅÆÆÅÅÆÆ
Ç   HOSTS file		ÇÈ   DNS server cache

Computer properties allow you to change the DNS computer name. The concatenation of the computer name and the domain DNS name results in the FQDN Fully Qualified Domain Name.

Keyboard Exercise

Investigate your DNS server with the MMC DNS console.