An Introduction to Computer Networks

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In this tutorial, we will introduce you to the world of computer networks. We give a brief introduction of what is computer networks, explore the need of studying the subject and look into the brief history of developments in this field. This tutorial also gives an insight of the process to connect to a network.

What is Computer network ?

– A set of computers connected together in an organised manner to transfer data from one
computer to other is called a computer network
– Connected computers on a network are called nodes.
– The computers can be connected via cables, most commonly the Ethernet cable, or
wirelessly through radio waves.
– Connected computers can share resources, like access to the Internet, printers, file servers
etc.

What is networking and why do we study it?

– The engineering discipline that aims to study computer networks is computer networking.
– It is studied to analyze the process of communication within a computer network or transfer
of information among various computer networks.

A brief history of computer networking

The chronology of significant computer-network developments includes:

Late 1950s:

Early networks of computers included the U.S. military radar system Semi-Automatic Ground Environment (SAGE).

1959:

Anatolii Ivanovich Kitov proposed to the Central CommiTTee of the Communist Party of the Soviet Union a detailed plan for the re-organisation of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centres, the OGAS.

1960:

Commercial airline reservation system semi-automatic business research environment (SABRE) went online with two connected mainframes.

1963:

J. C. R. Licklider sent a memorandum to office colleagues discussing the concept of the “Intergalactic Computer Network”, a computer network intended to allow general communications among computer users.

1964:

Researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at MassachuseTTs Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections.
A set of computers connected together in an organised manner to transfer data from one
computer to other is called a computer network.
Connected computers on a network are called nodes.
The computers can be connected via cables, most commonly the Ethernet cable, or
wirelessly through radio waves.
Connected computers can share resources, like access to the Internet, printers, file servers
etc.

Throughout the 1960s:

Paul Baran and Donald Davies independently developed the concept of packet switching to transfer information between computers over a network. Davies pioneered the implementation of the concept with the NPL network, a local area network at the National Physical Laboratory (United Kingdom) using a line speed of 768 kbit/s.

1965:

Western Electric introduced the first widely used telephone switch that implemented true computer control.

1966:

Thomas Marill and Lawrence G. Roberts published a paper on an experimental wide area network (WAN) for computer time sharing.

1969:

First four nodes of the ARPANET were connected using 50 kbit/s circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, and the University of Utah.
Leonard Kleinrockcarried out theoretical work to model the performance of packet- switched networks, which underpinned the development of the ARPANET. His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today.

1972:

Commercial services using X.25 were deployed, and later used as an underlying infrastructure for expanding TCP/IP networks.

1973:

French CYCLADES network was the first to make the hosts responsible for the reliable delivery of data, rather than this being a centralized service of the network itself.
Robert Metcalfe wrote a formal memo at Xerox PARC describing Ethernet, a networking system that was based on theAloha network, developed in the 1960s byNorman Abramson and colleagues at the University of Hawaii.

July 1976:

Robert Metcalfe and David Boggs published their paper “Ethernet: Distributed Packet Switching for Local Computer Networks” and collaborated on several patents received in 1977 and 1978.
John Murphy of Datapoint Corporation created ARCNET, a token-passing network first used to share storage devices.

1979:

Robert Metcalfe pursued making Ethernet an open standard.

1995:

Transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s.

1998:

Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 100 Gbit/s were added (as of 2016). The ability of Ethernet to scale easily (such as quickly adapting to support new fibre optic cable speeds) is a contributing factor to its continued use.
(Source of history: Wikipedia)



What happens when you type “www . facebook . com” in the url tab (connecting to a network)
Tutorialwing: Connect to A Network introduction to network

Tutorialwing: Connect to A Network

Let’s go step by step to understand the process –
A. Let us assume a network.
B. A network has many hosts. One of the hosts may be your computer.
C. A host has various processes. Assume you open your browser and type www . facebook . com.
D. Now facebook’s network is in some other country and this network also has various hosts
which further have a lot of processes. This is one process that we wish to connect to.
E. We type the domain www . facebook . com.
F. Using this domain we have to identify:
  1. Network name
  2. Host name
  3. Process name
G. ISP provides a service Called domain name service.
H. Domain name server converts the alphanumeric address www . facebook . com to IP address.

Tutorialwing-  Diagramatic representation of connecting to a network Computer Networks Tutorial

Tutorialwing- Diagramatic representation of connecting to a network

I. Before contacting www.facebook.com we contact DNS and seek for the IP address of www.facebook.com. DNS then returns its IP address.
J. Converting the domain name to IP address is an overhead. So after the first time we visit DNS to fetch the IP address, we save the address for some time. Whenever the service expires we again visit DNS.
K. Thus, once we get the IP address we reach to the network => host => Process.
L. This is how we connect to Facebook.

This tutorial was thus an insight into the networks world. To move ahead, we study Classful addressing in the incoming tutorial

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