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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).
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
External world / Global Network
YYY corporation
ZZZ corporation
YYY corporation
ZZZ corporation
VPN
VPN
Proxy Server
Firewall
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first.yyy.com. second.yyy.com. third.yyy.com. third.zzz.com.first.zzz.com. second.zzz.com.
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Zone.Name.
Primary Zone Secondary Zone
Zone.Name.
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