Domain Name System (DNS) is comparable to a telephone book where each computer using the server has the Internet Protocol (IP) address and a host name. Typically, when the user of one computer needs to link to another, he/she must enter the host name. The computer will then contact the DNS server which will conduct a cross-reference of the actual IP address and the host name provided. If the DNS server have the data of the host name and it matches with the IP address, then it facilitate the connection with the remote computer (IBM, 2006). In simple terms, DNS locate the host name of the computer provide and provide the information associated with the computer such as IP address when the user enters the DNS name of a computer in an application. The main objective of this paper is to estimate the number of DNS server needed for the expansion of the organizations’ operations and the types of DNS server to be installed in each branch.
The use of DNS as a name system is the easiest way of accessing network resources since it allows the users to refer to service or computer by a name which is easier to remember. The main function of the DNS is to locate host name and provides the numeric address that applications and operating systems needs to identify the computer on a network (Hall, & Eller, 2005). For example, when the users’ wants access Microsoft website, they enter www.microsoft.com as opposed to entering the server’s numeric IP address which is required to access the Microsoft Web server through the internet.
DNS serves requires regular maintenance for small, medium and large-sized organizations in order to ensure effective and efficient functionality. Generally, small and medium-sized organization requires the installation of between 1 to 4 DNS servers. While large medium-sized organization typically requires the installation of between 4 and 14 DNS servers. In order to accurately estimate the number of DNS servers and the type of the DNS server that the organization should install in each branch, it is prudent to understand how DNS works.
How DNS works
DNS database works by translating the host name into IP address. In the computer language, clients are referred to as resolvers in the DNS and the servers are referred to as name servers. The work of the DNS is accomplished through three components: domain name space, name server and resolver (IBM, 2006). Typically, the resolver transmit queries to a name server. In return, the name server re-transmit the requested information, a pointer to another name server. In case the queries cannot be satisfied, a failure message is return.
DNS utilizes Transmission Control Protocol (TCP) and User Datagrams Protocol (UDP) as the foundation protocols. Generally, resolvers send UDP queries to servers for performance reasons. But if the return data occurs in truncation format, resolver resorts to TCP.
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Resolvers
The main purpose of the resolver is to provide users with address information regarding their computer on the network (Hall, & Eller, 2005). The resolvers passes the query to the name servers which contain the IP address of the Web site. This means that the host computers and the application have a resolver as built in library routine.
Name servers
Name servers function as storage of database for the address information about all the computer on the network. This means that when the client send a query about the address information about specific computer, the name servers locate the information send to the clients’ computer in the form of IP address. The name servers are arranged into hierarchical grouping with different levels known as domains.
The root-level domain are not named since it is understood in all the DNS names. It contain a restricted number of subdomains which assists in organizing the DNS namespace. These subdomain are limited in number and forms part of most inclusive DNS namespace as well as the highest-level that people uses thus named top-level domain. The top-level domain are grouped into two categories: geographical and functional (IBM, 2006). Geographical top-level domain tells the region or the country in which the organization that registered the domain in located. The functional top-level domain indicates the function of the organization that registered a subdomain. Some of the commonly used top-level domains are presented in the table below.
| Domain | Description |
| .xx | Two-letter country code |
| .com | commercial organizations |
| .edu | Educational institutional and universities |
| .org | Not-for-profit organizations |
| .net | Networks |
| .gov | Nonmilitary government organizations |
| .mil | Military government organizations |
| .num | Phone numbers |
| .arpa | Reverse DNS |
Therefore, the estimated number of DNS server that the organization can install ranges from 4 to 14 since it is a large medium-sized organization. The two types of DNS server that the organization should install in each branch is primary and secondary name servers (Hall, & Eller, 2005). Primary name servers gathers the data from local DNS database files. Secondary name server extract information from the primary name servers. Since the organization communicate with the outside world, it will be prudent to create both external and internal namespace.
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