DNS is the backbone of Active Directory for two reasons: domains are named using DNS and domain controllers are located using DNS. So if DNS is not set up properly, client computers will not be able to locate domain controllers and users will be unable to log on to the network and access resources. Since DNS is critical to the operation of WS2003-based networks, I’ll begin by briefly reviewing basic DNS concepts while keying in on various issues relating to DNS on WS2003. For a more detailed look at DNS on Microsoft platforms, see DNS on Windows 2003 (O’Reilly).
DNS is a client/server, Internet-standard protocol that implements a hierarchical naming system using a distributed database for associating names of hosts with IP addresses. This database is stored on DNS servers in the form of zones containing resource records, and DNS clients query these servers to resolve hostnames into IP addresses. DNS queries can be issued by DNS clients to DNS servers or by DNS servers to other DNS servers, and this system of queries is an essential part of the name-resolution process.
Let’s unpackage that brief description in more detail.
The DNS namespace is hierarchical in structure and starts with a root domain represented by a period. Beneath the root domain are top-level domains, which are either functional (.com, .org, .edu, and so on) or geographical (.us, .ca, .uk, and so on). Beneath these top-level domains are second-level domains, usually ...