Name or the Number!

      What if the internet addresses were just numbers and not the easy-to-remember today (202.185.130.251 as opposed to hotmail.com)? Beyond the veil of site names, the internet actually works on the site numbering system. These numbers, called Internet Protocol (IP) addresses are cryptic 32-bit numbers that are the Internet's equivalent of a telephone number in real life. Every computer connected to the internet, including yours when you are online, has an IP address.
       The IP routing system, which is the heart of the Internet, is responsible for transferring data between computers given the IP addresses of the sender and receiver. The add-on Transmission Control Protocol (TCP) layer insures accuracy in data transmission. This combination called TCP/IP, works fine except for one problem-IP addresses are hard to remember.

Name Or The Number
       To solve this problem we have what is called the domain name system, a system where all computers are given a name that can be easily understood. Public directories, called domain name server (DNS), maintain a distributed list of all such domains names against their IP addresses. This way, when you tell your browser to take you to www.suite101.com, your browser queries a DNS for the IP address of the domain name www.suite101.com. Upon obtaining the IP, it continues with accessing the site.
      The domain name system consists of two parts. The first part, the resolver, operates out of your PC and queries a domain name server when needed. The second part is the domain name server itself. When you browser requires the IP address of a particular site, the resolver queries the nearest name server. If the server knows it replies immediately (the database is distributed, remember?), else the name server's resolver component queries another name server. When the answer is found, it travels backwards through all the name server that were along the way, down to your PC. The name server that could finally answer the query is called the Authoritative Server; the other update their database to include the address so that they will know the answer the next time a PC comes asking.
       This process can sometimes take a painfully long time, causing the computers to tire of waiting and report a 'DNS entry not found' error. Hitting the refresh or reload button usually solves this problem because the nearest name server will have the answer ready.
       An name server, therefore, has two roles, one as a server for domain name looksup and the other as a super-resolver to extend the functionality of the PC's primitive resolver. No one server maintains the entire database of domain names; it is distributed  across thousands of server's resolver therefore performs the task of looking for the answer to a particular query. An important part of this looking around depends on the way Web sites are named.

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