Welcome to this week's installment of "Learn Windows XP Professional in 15 Minutes a Week," the 18th in this series. This article will provide a beginning overview of the DNS service provided by Windows 2000 server and how it interacts in Windows XP Professional environments.
Domain Name System Overview
Domain Name System (DNS) servers maintain a distributed database used to translate computer names to Internet Protocol (IP) addresses on Transmission Control Protocol/Internet Protocol (TCP/IP) networks (which includes the internet).
[NOTES FROM THE FIELD] - Being able to install DNS is not a requirement for the 70-270 exam. Understanding the functionality of DNS and how it affects Windows XP Professional clients in workgroups and within domains is.
In the next few weeks in my "Learn Active Directory in 15 Minutes a Week" series of articles I will cover DNS in more depth, including a more in-depth view of installing DNS.
The Microsoft Domain Name System (DNS) is the name resolution service that resolves Uniform Resource Locator names (URLs) and other DNS names into their "true" dotted decimal format. For example, http://www.zandri.net translates into a specific Internet Protocol (IP) address, and it is that address resolution that allows you to reach the server destination you are seeking.
Lookup Queries and Lookup Types
There are two different types of DNS lookup: forward and reverse. A forward lookup query resolves a DNS name to an IP address and is the most common DNS query. A reverse lookup query resolves an IP address to a name.
A DNS name server can resolve a query only for a zone for which it has authority. When DNS servers receive a resolution request, they attempt to locate the requested information in their own database.
Two types of queries can be performed in DNS: Iterative and Recursive.
A DNS resolution query made from a client to a DNS server where the server returns the best answer it can based on its local cache or stored zone data is called an iterative query. If the server performing the iterative query does not have an exact match for the name request, it provides a pointer to an authoritative server in another level of the domain namespace. The client system will then query that server and will continue this process until it locates a server that is authoritative for the requested name or until an error is returned, such as name not found, or a time-out condition is met.
A DNS resolution query made from a client to a DNS server in which the server assumes the full workload and responsibility for providing a complete answer to the query is called a recursive query.
The server, if it cannot resolve the resolution from its own database, will then perform separate iterative queries to other servers (on behalf of the client) to assist in returning an answer to the recursive query. It will continue this process until it locates a server that is authoritative for the requested name or until an error is returned, such as name not found, or a time-out condition is met.
In most cases, client computers send recursive queries to DNS servers. Usually the DNS server is set up to make iterative queries to provide an answer to the client.