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External world / Global Nezzzrk
YYY corporation
ZZZ corporation
YYY corporation
ZZZ corporation
VPN
VPNProxy Server
Firewall
A
DNS Server, Firewall, VPN or Proxy Server
A
DNS Client
first.yyy.com. second.yyy.com. third.yyy.com. third.zzz.com.first.zzz.com. second.zzz.com.
. zzz.com.
yyy.com.
yyy.com.
yyy.com. zzz.com. someother.com.
com.
.
1
2
3
1
2
Zone.Name.
Primary Zone Secondary Zone
Zone.Name.
3
4
5
6
4
5
6
Starting with an example when a corporate computer needs to resolve an internal
name (follow the above figure for illustrations).
A computer in the YYY Corporation needs to resolve a DNS query for
www.third.yyy.com. First it finds that the name www.third.yyy.com. is internal based
on PAC file. Therefore, it submits the query to the assigned DNS server (Step 1). If
this DNS server is authoritative for the name www.third.yyy.com. or the cache
contains necessary data, then the server will respond to the client. Otherwise the
server will query a root server (Step 2). A root server returns a reference to the
authoritative server (Step 3). Then the server sends a query to the authoritative
server zone (Step 4), receives a response from it (Step 5) and finally passes it to
the client (Step 6).
A computer in the ZZZ Corporation needs to resolve a DNS query for
www.third.zzz.com. It submits the query to the assigned DNS server (Step 1). If this
DNS server is authoritative for the name www.third.yyy.com. or the cache contains
necessary data, then the server will respond to the client. Otherwise the server
Windows 2000 White Paper 50