Computer Network Tutorial

What is Internet?

  • Internet means connecting a computer to any other computer anywhere in the world via routers and servers.
  • Router is a device that determines the next network point to which a packet should be forwarded towards the destination.
  • The NT server, along with the bandwidth of the communication circuit to which it is attached, determines the capacity of web server.
  • Bandwidth is expressed in terms of megabit per second (Mbps).
Following figure shows the main components of Internet connection.

component of internet

Network edge

  • It consists of hosts, clients and servers.
  • In computer networks, computers connected to internet are known as hosts.
  • The hosts are also called as end systems.
  • The end system can send and receive all kinds of information such as text, graphics, voice, video, and computer programs.
  • The hosts are divided into clients and servers.
  • Clients are desktop and  mobile PCs while servers are more powerful devices such as web server and mail server.

Connection oriented and connectionless services

There are two services provided by the layer:

1. Connection oriented services

  • In connection oriented service, when one party wants to send or receive data from another party, the following operations occur:
           i. Connection is established
           ii. Data is exchanged in both direction
           iii. The connection is released
  • Connection oriented service is more reliable than connectionless service.
  • It is also called as reliable network service.
  • This is a full-duplex service which means that the data can flow in both directions at the same time.
  • Connection oriented protocol makes a connection and checks whether message is received or not and sends it again.
  • Connection oriented service is stream based, it can guarantee that data will arrive in the same order.
  • TCP and SCTP are the example of connection oriented service.

2. Connectionless services

  • In connectionless service, there is no need of connection establishment and connection release for sending packets from sender to receiver.
  • The sender simply starts sending packets to the destination.
  • Each packet is routed independently from source to destination.
  • The order of packets sent can be different from the order received.
  • In connectionless service, the data is transferred in one direction from sender to receiver without checking that receiver is present there or not.
  • UDP is the example of connectionless service.