ABSTRACT
This chapter focuses on Domain Name System (DNS): what it is, how it is implemented, and many of the issues that DNS raises that one must confront. DNS is based on the client–server network model. The DNS infrastructure consists of three main components: a DNS client, a DNS server, and a DNS database. The DNS infrastructure consists of three main components: a DNS client, a DNS server, and a DNS database. The DNS client is usually called a DNS resolver. The DNS resolver is a set of library routines that provides access to one or more DNS servers. The DNS clients can send two types of queries to DNS servers. One is an iterative query and the other is a recursive query. DNS caching is a mechanism to store DNS query results locally for a period of time, so that the DNS client can have faster responses to DNS queries.
