Working Methodology of Domain Name Server
When we buy a computer, we start using it for our various requirements. We may use the computer to program a certain project, write codes for some software or do multiple tasks with the help of soft ware features available on the computer, mostly by default. This all does not need us to be in touch with the outside world.
However, when we need to interact with other people via our own computer for doing small jobs like email sending etc, we need to have an address for our computer. This address is known as IP address and is usually a string of numbers like 192.247.150.1. It is humanly not possible for us to remember this address all through. It is here that we need to register a domain name, which is usually a few words that can be remembered easily. When we need to go to a particular web site called URL, we need not to remember its IP address, but the DNS does the mapping of this address.. This is how it works.
Codes for names and numbers
DNS does the mapping and reverse mapping of addresses. When it starts finding an IP address from a URL, it is called mapping and when the IP address is scanned to know the URL connected to this address, it is called reverse mapping. Here is how the directory services of DNS helps it to interact with other DNS servers in the internet to find the address of a particular web site or URL Hence, the DNS can be said to be a global network of servers. It is thus a distributed database and no organization is responsible for updating it.
There are soft wares for the writing DNS programs. The most popular is BIND (Berkeley Internet Name Domain) In this software, DNS is hierarchical, tree-structured system. The top is known as the root of the system. Below this root, there are seven sub domain roots like ”com”, “org”, “gov”, “mil”, “edu”, “Int”, “net”
DNS has mainly two components; one is the “Name Server” and other “Resolver”
Name server has the task of looking up the names. A particular name server can do this for a number of addresses. However, if it does not have the required information, then it will contact other name server. Nevertheless, every name server also knows how to contact the root server that in turn will know the location of every authoritative name server for all level domains
Here are three types of name servers,-primary name server, secondary name server, and caching name server. The function of each of these name servers is to resolve name queries. Primary name servers own data base records, therefore any change in these have to be propagated to Secondary name servers, via a “ Zone Transfer” Caching name servers only resolve name queries but do not maintain any DNS database files.
The secondary name servers are configured for backup purposes.
How Caching Works
The caching server catches the required information and keeps it for a certain time called time to live (TTL) .When a process needs to determine an IP address given a DNS address; it calls upon the local host to resolve the address. This can be done in variety of ways, which is thru the “UNIX” system
When a name server receives a request for finding an address, it can answer by finding the IP address. This method is called iterative. In this, the client simply asks the server to resolve a domain name. The server accesses its database, finds its IP address and sends that back. If the server does not find the address, it sends back an error (DNS not Found).
A popular user interface, called 'nslookup'is available on the UNIX system, for performing any DNS function. This program also displays the result to the user. Using 'nslookup’.
To combat the security threats to the DNS system,the internet engineering task force (IETF) has come up with DNS security (DNSSEC) extensions to DNS protocol. The main objective to DNSSEC is to provide authentication and integrity to the DNS.