DOMAIN NAME SYSTEM (DNS)

DOMAIN NAME SYSTEM (DNS)

ABSTRACT

The essence of DNS is the invention of a hierarchical ,domain based naming scheme and a distributed database system for implementing this naming scheme.The naming scheme is interesting for two reasons. First ,it has been used to assign machine names through out the global internet. Second ,because it uses a geographically distributed set of servers to map names to address, the implementation of the name mapping mechanism provides a large scale example og the client-server paradigm. It is primarily used for mapping host names and email destinations to IP addresses but can also be used for other puposes . DNS is defined in RFCs 1034 and 1035.
The way DNS is used is as follows. To map a name onto an IP address,an applicaton program calls a library procedure called the resolver , passing it the name as parameter. The resolver sends a UDP packet to a local DNS server, which then looks up the name and returns the IP address to the resolver , which then returns it to the caller.Armed with the IP addess,the program can then establish a TCP connection with the destination ,or send it UDP packets.