Not my copyright!!!!!

1. By
Rachit Mehta 9TH D

2. •In September 1940, George Stibitz used a Teletype machine to send instructions
for a problem set from his Model at Dartmouth College to his Complex Numbers
Calculator in New York and received results back by the same means. Linking output
systems like teletypewriters to computers was an interest at the Advanced Research
Projects Agency (ARPA) when, in 1962, J.C.R. Licklider was hired and developed a
working group he called the "Intergalactic Network", a precursor to the ARPANET
•Early networks of communicating computers included the military radar system
Semi-Automatic Ground Environment(SAGE), started in the late 1950s
•The commercial airline reservation system semi-automatic business research
environment(SABRE) which went online with two connected mainframes in 1960.
•In 1964, researchers at Dartmouth 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.
•Throughout the 1960s Leonard Kleinrock, Paul Baran and Donald Davies independently
conceptualized and developed network systems which used packets that could be used
in a network between computer systems.
•1965 Thomas Merrill and Lawrence G. Roberts created the first wide area network .
•The first widely used telephone switch that used true computer control was introduced
by Western Electric in 1965.
•In 1969 the University of California at Los Angeles, the Stanford Research Institute,
University of California at Santa Barbara, and the University of Utah were connected as
the beginning of the ARPANET network using 50 Kbit/s circuits.
•Commercial services using X.25 were deployed in 1972, and later used as an underlying
infrastructure for expanding TCP/IP networks.

3. Computer Networks
Computer network
connects two or more
autonomous computers.
The computers can be
geographically located
anywhere.

4. Computer Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Email
Message broadcast
Remote computing
Distributed processing (GRID Computing)

5. CATEGORIES
OF
NETWORKS

6. Categories of networks

7. The way computers are connected
The network topology
defines the way in
which computers,
printers, and other
devices are connected.
A network topology
describes the layout of
the wire and devices as
well as the paths used
by data transmissions.
Please note= This topic is not in course but is necessary to know…

8. Computer Networks
Network in small geographical Area (Room, Building
or a Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area
Network)
Network spread geographically (Country or across
Globe) is called WAN (Wide Area Network)

9.  Allow resource sharing between computers.
 Computers
 Peripheral devices
 Transmission medium (e.g. cable)
3 types of topology
 Bus topology
 Star topology
 Ring topology

10. LANs Figure 6-4
 Hub –
 a device that facilitates connection
 LAN acts logically like a bus.
 Star –
the dominant topology today.

11. MAN

12.  Usesservices provided by a network service
provider. (Tel. Company)
 Individual users’ computers
 Organizations’ LANs
 Many Tel. Company provide a popular MAN service
called SMDS (Switched Multimegabit Data Services)
 Prior to SMDS's arrival in 1995,
the only way to connect LANs was through
a dedicated private line.

13. WAN

14.  Theconnection of individual computers or
LANs over a large area (country, world).
 Userusing a telephone line to connect to
an ISP (Internet Service Provider) is using
a WAN.
 Negotiates fee
 ISP
 Tel. company

15. Connecting devices

16. WiFI: Short for ‘wireless fidelity’. A term for certain types of wireless
local area networks (WLAN) that use specifications conforming to IEEE
802.11b. WiFi has gained acceptance in many environments as an
alternative to a wired LAN. Many airports, hotels, and other services offer
public access to WiFi networks so people can log onto the Internet and
receive emails on the move. These locations are known as hotspots.
LAN: A computer network that spans a relatively small area. Most LANs are
confined to a single building or group of buildings. However, one LAN can
be connected to other LANs over any distance via telephone lines and
radio waves.
There IS a difference between these two items. WiFi is a Wireless Network
like a wireless home network or a hotspot at a local coffee shop or the
airport or a WiFi cafe. A Wireless Card is an Adapter placed inside the
computer or the Laptop which is needed to access the WiFi Network you
wish to connect to.

17. •Communications satellites – The satellites use microwave radio as their
telecommunications medium which are not deflected by the Earth's
atmosphere. The satellites are stationed in space, typically 35,400 km
(22,000 mi) (for geosynchronous satellites) above the equator. These
Earth-orbiting systems are capable of receiving and relaying voice, data,
and TV signals.
• A global area network (GAN) is a network used for supporting mobile
across an arbitrary number of wireless LANs, satellite coverage areas,
etc. The key challenge in mobile communications is handing off the user
communications from one local coverage area to the next. In IEEE Project
802, this involves a succession of terrestrial wireless LANs.
• Terrestrial microwave – Terrestrial microwaves use Earth-based transmitter
and receiver. The equipment looks similar to satellite dishes. Terrestrial
microwaves use low-gigahertz range, which limits all communications to
line-of-sight. Path between relay stations spaced approx, 48 km (30 mi)
apart.