Domain Name Service (DNS)

The function of the DNS service is to resolve hostnames, such as, to IP addresses. Such a resolution system makes it possible for people to remember the names of, and refer to frequently used hosts, using the easy-to-remember hostnames rather than the hard-to-remember IP addresses.

Similar to other TCP/IP-based services, DNS is a platform-independent protocol. Therefore, it can be used on Linux, UNIX, Windows, NetWare, and almost every other platform.

On networks where there is no DNS server, it is possible to resolve hostnames to IP address using the HOSTS file; however, such environments are becoming increasingly rare. All common network operating systems now include DNS server application software.

The HOSTS file is a text file, found on almost all PC operating systems, in which you can place hostname-to-IP-address resolution information. When HOSTS files are used, it's up to the administrator to manually make changes to the file if needed.

This factor alone is sufficient to make the installation of a DNS server an obvious choice.

Windows Internet Name Service (WINS)

On Windows networks, a system called WINS enables Network Basic Input/Output System (NetBIOS) names to be resolved to IP addresses. NetBIOS name resolution is necessary on Windows networks so that systems can locate and access each other by using the NetBIOS computer name rather than the IP address. It's a lot easier for a person to remember a computer called secretary than to remember its IP address, The NetBIOS name needs to be resolved to an IP address and subsequently to a MAC address (by ARP).

NetBIOS name resolution can be performed three ways on a network. The simplest way is to use a WINS server on the network that will automatically perform the NetBIOS name resolution. If a WINS server is not available, the NetBIOS name resolution can be performed statically using a LMHOSTS file. Using a LMHOSTS file requires that you manually configure at least one text file with the entries. As you can imagine, this can be a time-consuming process, particularly if the systems on the network change frequently. The third method, and the default, is that systems will resolve NetBIOS names using broadcasts. There are two problems with this approach. First, the broadcasts create additional network traffic, and second, the broadcasts cannot traverse routers unless the router is configured to forward them. This means that resolutions between network segments are not possible.