.

1. Computer
Network
Introduction

2. What is a computer
network?
• A network is a group of
computers (or a group of
smaller networks) that are
connected to each other by
various means, so that they
may communicate with
each other. The internet is
the largest network in the
world.

3. History of Computer Networking and Internet
1. 1961-1972: Development and Demonstration
of Early Packet Switching Principles
2. 1972 - 1980: Internetworking, and New and
Proprietary Networks
3. 1980 - 1990: A Proliferation of Networks
4. The 1990s: Commercialization and the Web

4. 1961-1972: Development and Demonstration of
Early Packet Switching Principles
• History traced to early 1960s, a time at which the
telephone network was the world's dominant
communication network.
• Due to importance and high cost of computers there
was need to address how to hook computers together
such that they could be shared among geographically
distributed users.

5. 1961-1972: Development and Demonstration of
Early Packet Switching Principles(contd)
• Three research groups around the world, all unaware of
the others' work, began inventing the notion of packet
switching as an efficient and robust alternative to circuit
switching.
 Leonard Kleinrock, graduate student at MIT, used
queuing theory, demonstrated the effectiveness of the
packet-switching approach for bursty traffic sources.
 Paul Baran at the Rand Institute had begun
investigating the use of packet switching for secure
voice over military networks.
 Donald Davies and Roger Scantlebury at the National
Physical Laboratory in England, also developing their
ideas on packet switching.

6. 1961-1972: Development and Demonstration of
Early Packet Switching Principles(Contd)
• J.C. R. Licklider and Lawrence Roberts, colleagues of
Kleinrock's at MIT, went on to lead the computer
science program at the Advanced Projects Research
Agency (ARPA) in the US.
• The early packet switches were known as Interface
Message Processors (IMP's), on 1/5/1969, the first IMP
was installed at UCLA, shortly thereafter at Stanford
Research Institute, UC Santa Barbara, and the University
of Utah.

7. 1961-1972: Development and Demonstration of Early Packet
Switching Principles(Contd)
 By 1972, ARPAnet had grown to approximately 15 nodes, and was given
its first public demonstration by Robert Kahn at the 1972 International
Conference on Computer Communications.
 The first host-to-host protocol between ARPAnet end systems known
as the Network Control Protocol (NCP) was completed in 1972 and
applications could be written. First e-mail program by was written by
Ray Tomlinson at BBN in 1972.

8. 1972 - 1980: Internetworking, and New and
Proprietary Networks
• Early to mid 1970's, additional packet-switching
networks besides ARPAnet came into being;
1. ALOHAnet, a satellite network linking
together universities on the Hawaiian islands.
2. Telenet, a BBN commercial packet-switching
network based on ARPAnet technology.
3. Tymnet; and Transpac, a French packet-
switching network.
• Pioneering work on interconnecting networks was
done by Vinton Cerf and Robert Kahn

9. 1972 - 1980: Internetworking, and New and
Proprietary Networks(Contd)
 Digital Equipment Corporation (Digital)
released the first version of the DECnet in
1975, allowing two PDP-11 minicomputers to
communicate with each other. OSI protocol
suite is based on ideas pioneered in DECnet.
 Other important players during the 1970's
were Xerox (with the XNS architecture) and
IBM (with the SNA architecture).
 In the 1980's (and even before), researchers
were also developing a "competitor"
technology to the Internet architecture. These
efforts have contributed to the development of
the ATM (Asynchronous Transfer Mode).

10. 1980 - 1990: A Proliferation of Networks
 By the end of the 1970's approximately 200 hosts were
connected to the ARPAnet. By the end of the 1980's the
number of host connected to the public Internet, would
reach 100,000.
 Much of the growth in the early 1980's resulted from
several distinct efforts to create computer networks
linking universities together:
1. BITnet (Because It's There NETwork) provided email and file
transfers among several universities in the Northeast USA.
2. CSNET (Computer Science NETwork) was formed to link
together university researchers without access to ARPAnet.
3. In 1986, NSFNET was created to provide access to NSF-
sponsored supercomputing centers. Starting with an initial
backbone speed of 56Kbps, NSFNET's backbone would be
running at 1.5 Mbps by the end of the decade, and would be
serving as a primary backbone linking together regional
networks.

11. 1980 - 1990: A Proliferation of Networks(contd)
 Paralleling this development of the ARPAnet (which
was for the most part a US effort), in the early 1980s
the French launched the Minitel project, an
ambitious plan to bring data networking into
everyone's home.
 Sponsored by the French government, the Minitel
system consisted of a public packet-switched
network (based on the X.25 protocol suite, which
uses virtual circuits), Minitel servers, and inexpensive
terminals with built-in low speed modems.
 The Minitel became a huge success in 1984 when the
French government gave away a free Minitel
terminal to each French household that wanted one.

12. The 1990s: Commercialization and the Web
• In the 1990’s the ARPAnet, the progenitor of the Internet
ceased to exist.
• MILNET and the Defense Data Network had grown in the
1980's to carry most of the US Department of Defense
related traffic and NSFNET had begun to serve as a
backbone network connecting regional networks in the
United States and national networks overseas.
• In 1991, NSFNET lifted its restrictions on use of NSFNET
for commercial purposes. NSFNET itself would be
decommissioned in 1995, with Internet backbone traffic
being carried by commercial Internet Service Providers.
• The main event of the 1990's however, was to be the release
of the World Wide Web, which brought the Internet into the
homes and businesses of millions and millions of people,
worldwide.

13. The 1990s: Commercialization and the Web(contd)
 The WWW was invented at CERN by Tim Berners-Lee
in 1989-1991, based on ideas originating in earlier work
on hypertext from the 1940's by Bush and since the
1960's by Ted Nelson.
 During the 1990's, networking research and
development also made significant advances in the areas
of high-speed routers and routing and local area
networks.
 The technical community struggled with the problems
of defining and implementing an Internet service model
for traffic requiring real-time constraints, such as
continuous media applications.
 The need to secure and manage Internet infrastructure
also became of paramount importance as e-commerce
applications proliferated and the Internet became a
central component of the world's telecommunications
infrastructure.

14. Network building blocks
All networks, large or small, require specialized network hardware to make them
work. For small networks, the hardware may consist of nothing more than a collection of
computers that are equipped with network ports, a cable for each computer, and a
network switch that all the computers plug in to via the cable. Larger networks probably
have additional components, such as routers or repeaters.
Server
Client
Computer
Cable Network Switch

15. Computer Network’s benefits.
1. Hardware resource sharing
Networks are able to share one resource, such as a
printer, for numerous computers. This allows many individual
computers to access a single network resource. This saves
money and space for the organization
2. Data sharing
Once networks were setup, people found that the
next best thing was the ability to easily share documents. The
type of server that stores files is called a file server. Data can
be in the form of text, images, numbers or characters

16. Computer Network’s
benefits.
3. Enhance communication
People in distant place can communicate
in real time. Gone of the days of snail mail,
where your message can take days before it
reaches the receiver. With email and chat ,
communication can be done in a flash.
4. Work better
Many organizations use networks for
many purposes such as making schedule for
colleagues, pick up days for meetings (when
everybody will be able to attend) and provide
useful online connections for network-linked
employees. Employees can communicate on a
network with other employees through email.

17. Computer Network’s benefits.
5. Shared Programs
Server or Network based programs are
programs that are loaded onto an online server or
network as opposed to directly onto the individual
computers. This program can therefor be accessed
by any computer possessing the correct amount
of bandwidth and system specifications. In short it
uses the server as an application server.
6. It boost storage capacity
Increasing storage capacity - you can
access files and multimedia, such as images and
music, which you store remotely on other
machines or network-attached storage devices.

18. Computer Network’s
disadvantages.
1. Security threat
With the large number of people that connects to
the network, there is a high possibility that an illegal activity
may occur such as; data piracy, hacking, illegal sharing of
resources etc.
2. Lack of Robustness
If the main server of the network will breakdown ,
the entire system would be useless. People can’t connect and
access network resource if the system will be down.
3. Virus and Malwares
Virus and malwares were shared in the network. Those
network with weak security is an easy target for malwares and
virus that will spread in your network to hack information , or
just to bring down the system.

19. Computer Network’s
disadvantages.
4. Undesirable behavior
It has been observed that providing users with internet connectivity has fostered
undesirable behavior among them. Considering that the web is a minefield of
distractions—online games, humor sites and even porn sites—workers could be
tempted during their work hours. The huge network of machines could also encourage
them to engage in illicit practices, such as instant messaging and file sharing, instead of
working on work-related matters. While many organizations draw up certain policies
on this, they have proven difficult to enforce and even engendered resentment from
employees.
5. Requires highly technical skills
For a computer network to work efficiently and optimally, it requires high technical
skills and know-how of its operations and administration. A person just having basic
skills cannot do this job. Take note that the responsibility to handle such a system is
high, as allotting permissions and passwords can be daunting. Similarly, network
configuration and connection is very tedious and cannot be done by an average
technician who does not have advanced knowledge.

20. Conclusion
Computer network offers a lot from
increase productivity in the
workplace, instant communication
and recreation in any form etc., but
let us bear in mind that there are
people who used it negatively to gain
something or to disrupt production.

21. Assignment
Direction:
Submit a document containing a picture of You utilizing computer
network and its advantage. Include a 2-paragraph discussion depicting
the impact of network to your life. Submit your work to my email
amoso@mlgcl.edu.ph on April 21, 2022