PRESENTATION

 PRESENTATION

DOMAIN NAME SYSTEM

 Each domain name has a corresponding IP address 

When the user types the domain name in the address bar, the corresponding IP address is supplied. Such a translation is possible with the help of system called DNS (DOMAIN NAME SYSTEM) 

DEFINITION: “DOMAIN NAME SYSTEM is a collection of the databases that contain information about domain names and their corresponding IP address.” 

 

PURPOSE OF NAMING

Addresses are used to locate objects 

Names are easier to remember than numbers 

You would like to get to the address or other objects using a name 

DNS provides a mapping from names to resources of several types 

 

DOMAIN NAME 

Domain name is a way to identify and locate computers connected to internet 

No two organizations can have same domain name 

A domain name always consists of two or more components separated by periods called dots (.) EXAMPLE: www.yahoo.co.in, www.facebook.com etc. 

Once a domain has been established subdomains can be created within the domain 

EXAMPLE: The domain for the large company could be “Vni.com” and within this domain subdomains can be created for each of the company’s regional office. Eg: Bombay.vni.com 

 

 STRUCTURE OF DOMAIN NAME

Last name. subdomain. second-level domain. top-level domain EXAMPLE: vijay.Bombay.vni.com 

 

IP address of www.google.com 

TOP LEVEL DOMAINS

 Top level domains are classified into 3 categories: 

Organizational or generic domains 

Geographical or country domains 

Reverse domains 

 

 ORGANIZATIONAL / GENERIC DOMAINS

 It consists of three character code which indicates the primary function of the organization or their generic behavior 

Most commonly used top level domains are: 

.com for commercial organization eg www.yahoo.com 

.net for networking organizations eg www.zedge.net  

.gov for government organizations eg www.newjersey.gov 

 

GEOGRAPHICAL / COUNTRY DOMAINS

It consists of two characters which represents different countries/regions all around the world 

These codes have been standardized by International Standard Organizational (ISO) 

EXAMPLE:  .in -> India  .jp -> Japan  .us -> United States etc..

WORKING OF DNS:

 When an application program needs to communicate with other computer, it needs to translate the name and the other computer into its IP address. The applications program that requests the service then becomes the client of DNS. 

It then sends the request to DNS server. The server looks up the name and then returns correct IP address. 

A large number of DNS servers may be involved to get the right IP address. After receiving the correct IP address, the communication between two computers starts. 

 

FEATURES OF DNS

Data is maintained locally, but retrievable globally 

No single computer has all DNS data 

DNS lookups can be performed by any device 

Remote DNS data is locally catchable to improve performance

No limit to the size of the database 

One server has over 20,000,000 names 

No limit to the number of queries 

24,000 queries per second handled easily 

Queries distributed among masters, slaves, and caches 

Database can be updated dynamically 

Add/delete/modify of any record 

Modification of the master database triggers replication 

Only master can be dynamically updated 

Creates a single point of failure 

 Data is replicated 

Data from master is copied to multiple slaves

Clients can query 

- Master server 

- Any of the copies at slave servers 

Clients will typically query local caches 

DNS protocols can use either UDP or TCP. If UDP, DNS protocol handles retransmission, sequencing, etc.