1. © McLean 20061 HIGHER COMPUTER NETWORKING Lesson 4: Domain Name Service Description of domain names and name resolution Domain name servers and domain name resolution

2. © McLean 20062 HIGHER COMPUTER NETWORKING What You Should Know About DNS Domain names IP addresses are difficult to remember so Domain Names are used to identify them instead. When we connect to a remote computer using a domain name such as google.com, a system known as the Domain Name Service (DNS) translates the domain name into an IP address This is a technique known as Name Resolution.

3. © McLean 20063 HIGHER COMPUTER NETWORKING What You Should Know About DNS Domain name servers A hierarchy of Domain Name Servers store the IP Addresses of all Domain Names used on the Internet. When a client of a DNS requests a connection to a Domain Name e.g. google.com the local DNS on a LAN searches through it’s database and returns the associated IP Address e.g. 216.239.39.99. If the local DNS does not contain the IP Address for the requested Domain Name then the request is passed to another DNS server on the Internet and so on until it is resolved.

4. © McLean 20064 HIGHER COMPUTER NETWORKING What You Should Know About DNS Domain name syntax Domain Names are divided into 2 parts e.g. google.com The company or organisation Domain Name followed by a suffix or Domain Name Ending. Some of the most common DN suffixes are listed below. DN Ending Meaning.com Commercial business, a company.net Network or Internet Service Provider.gov Governmental agency.edu Educational institution.org Non-profit institution