Domain Naming Service in computer networks

Domain Naming Service in computer networks

• 1.
  DNS
• 2.
  DNS in theInternet DNS is a protocol that can be used in different platforms. It translates human readable domain names (for example, www.amazon.com) to machine readable IP addresses (for example, 192.0.2.44). In the Internet, the domain name space (tree) was originally divided into three different sections: • generic domains, country domains, and the inverse domains.
• 5.
  Country Domains
• 6.
  Resolution •Mapping a nameto an address is called name-address resolution. •DNS is designed as a client-server application. A host that needs to map an address to a name or a name to an address calls a DNS client called a resolver. •The resolver accesses the closest DNS server with a mapping request.
• 7.
  CONTINUED.. • If theserver has the information, it satisfies the resolver; otherwise, it either refers the resolver to other • servers or asks other servers to provide the information. • After the resolver receives the mapping, it interprets the response to see if it is a real resolution or an • error, and finally delivers the result to the process that requested it. • A resolution can be either recursive or iterative.
• 8.
  Recursive Resolution • Theapplication program on the source host calls the DNS resolver (client) to find the IP address of the destination host. • The resolver, which does not know this address, sends the query to the local DNS server (for example,dns.anet.com) running at the Anet ISP site (event 1).
• 9.
  Recursive Resolution
• 10.
  Iterative Resolution • Initerative resolution, each server that does not know the mapping sends the IP address of the next Server back to the one that requested it. • Normally the iterative resolution takes place between two local servers; the original resolver gets the final answer from the local server.