yyy.com.
YYY corporation 
Proxy Server
.
com.
zzz.com.
External world / Global Nezzzrk
VPN | VPN | Firewall |
someother.com.
ZZZ corporation
2
first.yyy.com.
|
|
| YYY |
|
| . | corporation |
3 |
| yyy.com. | |
4 |
| ||
|
| ||
| 5 |
|
|
| second.yyy.com. third.yyy.com. | ||
ZZZ | 2 |
|
corporation |
| |
| zzz.com. | |
|
| |
|
| yyy.com. |
| 5 | 3 |
| 4 | |
|
|
first.zzz.com. 
second.zzz.com. 
third.zzz.com.
1 | 6 | 1 | 6 |
Zone.Name.
Primary Zone | Zone.Name. | Secondary Zone |
|
A DNS Server, Firewall, VPN or Proxy Server
A DNS Client
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 |