Explain how DNS works and the Services Provided by DNS
Answer:-
Overview of How DNS Works:
The application will invoke the client side of DNS, specifying the hostname that needs to be translated.
DNS in the user’s host then takes over, sending a query message into the network.
This mapping is then passed to the invoking application.
▫ A simple design for DNS would have one DNS server that contains all the mappings.
▫ Although the simplicity of this design is attractive, it is inappropriate for today’s Internet, with its vast (and growing) number of hosts.
Services Provided by DNS:
The DNS is
(1) a distributed database implemented in a hierarchy of DNS servers.
(2) an application-layer protocol that allows hosts to query the distributed database.
DNS provides a few other important services in addition to translating hostnames to IP addresses:
Host aliasing: A host with a complicated hostname can have one or more alias names. For example, a hostname such as relay1.west-coast.enterprise.com could have, say, two aliases such as enterprise.com and www.enterprise.com .
Mail server aliasing: For obvious reasons, it is highly desirable that e-mail addresses be mnemonic. For example, if Bob has an account with Yahoo Mail, Bob’s e-mail address might be as simple as bob@yahoo.mail.
Load distribution: DNS is also used to perform load distribution among replicated servers, such as replicated Web servers. Busy sites, such as cnn.com , are replicated over multiple servers, with each server running on a different end system and each having a different IP address.