Microsoft windows 2000 DNS manual Com Yyy.com Zzz.com

forwards the query to the DNS server containing the zzz.com. zone (Step 2). This server finds a delegation to the third.zzz.com. in the zzz.com. zone. It sends the query to that server (Step3) receives back the response (Step 4), passes it to the previous server (Step 5), which finally returns it to the client (Step 6).

			.
				5		4
	3	4		6
		5	com.		7
				7
		6
		8								8	9
yyy.com							zzz.com					someother.com.
2	9	External world / Global Network
YYY corporation											ZZZ corporation
Proxy Server		VPN		VPN				Firewall
						3			10

10

1

	YYY	ZZZ	2
.	corporation	corporation	zzz.com.
yyy.com.			yyy.com.
			11

first.yyy.com. second.yyy.com. third.yyy.com. first.zzz.com. second.zzz.com. third.zzz.com.

1 12

Zone.Name. Primary Zone Zone.Name. Secondary Zone

A DNS Server, Firewall, VPN or Proxy Server

A DNS Client

Now consider the example of a corporate computer that needs to resolve an external name (that does not belong to its company).

A computer in the YYY Corporation needs to open a web page on the www.someother.com. machine. Since it is a proxy client it sends a request to the proxy server (Step 1) after it finds that the name www.someother.com. is external based on the PAC file. The proxy server sends a DNS query to the assigned DNS server (Step 2) which recursively resolves the query. It sends a query to the root server (Step 3) and receives a reference to the server that contains the com. zone (Step 4). Then it sends the query to that server (Step 5) and receives a reference to the server that contains a zone someother.com. (Step 6). It sends a query to the latter (Step 7), which resolves the query and returns the response to the server

Windows 2000 White Paper

51