Introduction:
A collection of interconnected computers is called a Computer Network. Two computers or devices are said to be interconnected if they are capable of sharing and exchanging information with each other by following a protocol.
Advantages of Computer Networks:
• Resource sharing
• Improved communication
• Reduced communication cost
• Reliability of data
• Central storage of data
Evolution of networking:
1969:
First network ARPANET (ADVANCED RESEARCH PROJECT AGENCY NETWORK) came into existence
MID 80’S:
National science foundation created another high-speed network -NSFNET (NATIONAL
SCIENCE FOUNDATION NETWORK) which allowed only academic research on its network.
1990’s:
Internetworking of ARPANET, NSFnet and other privates networks lead to Internet. Internet is the network of networks.
Internet and functioning of the internet.
The world wide network of computers is called Internet. It connects many smaller networks together and allow all the computers to exchange information with each other.
Internet functioning:
All the computers connected to the internet uses the same set of rules for communication. That set of rules are called protocols. The communication protocol use by internet is
TCP/IP. TCP:
Transmission control protocol:- responsible for dividing the files or message at source computer into packets and reassembling them at destination computer.
IP:
Internet Protocol responsible for handling the address of destination computer.
Interspace:
Interspace is a client/server software program that allows multiple users to communicate online with real time audio, video and text data in dynamic 3D environments.
Switching techniques:
Different types of switching techniques are employed to provide communication between two computers. These are
Circuit switching:
First the complete physical connection between two computers is established and then the data are transmitted from the source computer to the destination. When a call is placed the switching equipment within the system seeks out a physical copper path all the way from the sender to the receiver. It is a must to set up an end-to-end connection between computers before any data can be sent. The circuit is terminated when the connection is closed. In-circuit switching, resources remain allocated during the full length of a communication, after a circuit is established and until the circuit is terminated and the allocated resources are freed.
Message Switching:
In this the source computer sends data or the message to the switching circuit which stores the data in its buffer. Then using any free link to the switching circuit the data is send to the switching circuit. Entire message is sent to the destination. It reaches through different intermediate nodes following the “store and forward” approach. No dedicated connection is required.
Packet Switching:
• Conceived in the 1960’s, packet switching is a more recent technology than circuit switching.
• Packet switching introduces the idea of cutting data i.e. at the source entire message is broken in smaller pieces called packets which are transmitted over a network without any resource being allocated.
• Then each packet is transmitted and each packet may follow any rout available and at destination packets may reach in random order.
• If no data is available at the sender at some point during a communication, then no packet is transmitted over the network and no resources are wasted.
• At the destination when all packets are received they are merged to form the original message.
• In packet switching all the packets of fixed size are stored in main memory.
