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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  Name Systems and TCP/IP Name Registration and Name Resolution            9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)                 9  TCP/IP Domain Name System (DNS)                      9  DNS Name Servers and Name Resolution                           9  DNS Resolution Concepts and Resolver Operations

DNS Name Resolution Efficiency Improvements: Caching and Local Resolution 1 2 3 DNS Reverse Name Resolution Using the IN-ADDR.ARPA Domain

In the previous topics I have described what name resolvers do, explained the basic top-down resolution process using iterative and recursive resolution, and discussed how local resolution and caching are used to improve resolution performance. Now I would like to tie all this background material together and finally show you how the name resolution process works as a whole!

As usual, the best way to do this is by example. Here, I will actually combine two examples I have used earlier: the fictitious company “XYZ Industries” and the non-existent college, Googleplex University. Let's say that XYZ Industries runs its own DNS servers for the “xyzindustries.com” zone. The master name server is called “ns1.xyzindustries.com”, and the slave is, ta-da, “ns2.xyzindustries.com”. These are also used as local DNS servers for resolvers on client machines. We'll assume for this example that as is often the case, our DNS servers will accept recursive requests from machines within our company, but will not assume other machines will accept such requests. Let's also assume that both the server and resolver perform caching, and that the caches are empty.

Let's say that Googleplex University runs its own DNS servers for the “googleplex.edu” domain, as I gave in the example in the topic describing DNS zones. There are three subdomains: finearts.googleplex.edu, compsci.googleplex.edu, and admin.googleplex.edu. Of these, compsci.googleplex.edu is in a separate zone with dedicated servers, while the other subdomains are in the “googleplex.edu” zone (this is shown in Figure 240.)

DNS Name Resolution Efficiency Improvements: Caching and Local Resolution 1 2 3 DNS Reverse Name Resolution Using the IN-ADDR.ARPA Domain