DNS makes short work of connecting to Internet addresses
Millions of people use DNS in Windows NT every day, although most of them do not know it. Anyone who types an address such as http://www.winntmag.com is using DNS to connect to a Web site. You need to know something about DNS if you want to connect your network to the outside world or prepare for conversion to Windows 2000 (Win2K).
Last month, I showed you how you can use WINS within your network to convert computer names to IP addresses. DNS performs a similar function outside your network, although in some cases it performs this function internally as well (e.g., in networks that include UNIX systems).
What Is DNS?
DNS is part of the TCP/IP family of protocols and utilities. Microsoft and other companies offer different versions of DNS that run on various OSs (most commonly the various versions of UNIX). The domain part of DNS refers to Internet domains, not the NT domain model.
The Internet is divided into domains, each of which serves a different group of users. These domains include .com, .edu, .gov, and .mil. A top-level Internet server, called a root name server (a name that makes sense if you think of the Internet as an inverted tree structure), manages each of these domains.
The Internet domain naming system queries these top-level Internet servers first, then works down the server tree. When you type an address, your local DNS server checks its database and cache for the requested data. If the local server does not have the IP address, it passes the request to the root name server. The root name server then passes the address of the appropriate name server to your DNS server. Your DNS server queries the name server for the server address at the next level down, and the process continues in this manner.
For example, if you want to connect to http://www.winntmag.com, your DNS server asks the .com domain server for the address of the winntmag name server in the .com domain. The local DNS server then uses the address it receives to ask the winntmag.com server for the address of the Web site host.
The preceding description applies to a sequential (or iterative) query, which DNS conducts server-to-server. DNS also conducts a recursive query, in which the domain name server passes its reply directly back to the original client.
To make both of these query processes more efficient, the DNS server caches the answers at each point in the search. After connecting to http://www.winntmag.com, if you want to connect to another .com server, your DNS server already has the address of the .com domain server. If you want to connect to another computer in the winntmag.com domain, your DNS server has cached the address of the winntmag.com name server and will not need to ask for it again.
WINS or DNS?
As I explained last month, both WINS and DNS provide name resolution, which is the process of converting a computer name to an address. WINS converts internal NetBIOS names to IP addresses, and DNS converts Internet-style names to IP addresses. If your network comprises just your company and is entirely Microsoft-based (i.e., NetBIOS-based), you do not need DNS; WINS will provide everything you need for name resolution. However, if you connect to the Internet, you will have to consider what type of connectivity you need to implement. If your users will be accessing external servers on the Internet, you need not provide them with anything more than a way to find an address on the Internet. If instead you will be providing resources that users outside of your network will connect to, you have to configure your servers (i.e., all machines that have resources to share) as hosts in your DNS database.
Even if you have decided that you do not need DNS right now, you will want to learn a little bit about it. In Win2K, WINS will merge with DNS to provide some much-needed automation for DNS configuration, which now is a manual process. DNS will then be part of Active Directory (AD), and will be the required name resolution protocol.
Installation
As with WINS and DHCP, DNS must run on an NT Server system. Install all three services from the Service tab in the Network applet in Control Panel. You must install them on a computer with a fixed IP address. After you have installed the software for DNS and rebooted your system, you will find that the installation adds DNS Manager to the Administrative Tools program group.
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