EXPERIMENT NO.

01

DATE OF PERFORMANCE: GRADE:

DATE OF ASSESSMENT: SIGNATURE OF LECTURER/ TTA:

AIM: Introduction to Computer Network.

THEORY:

COMPUTER NETWORK: By means of a computer network, it is an interconnected

set of autonomous computers. The term autonomous implies that the computers can
function independent of others. However, these computers can exchange information with
each other through the Communication network system. Computer networks have
emerged as a result of the convergence of two technologies of this century- Computer and
Communication. One significant development was the APPANET (Advanced Research
Projects Agency Network) Starting with four-node experimental network in 1969,Most of
the present-day concepts such as packet switching evolved from the ARPANET project.

APPLICATIONS:
Marketing and sales: Computer networks are used extensively in both marketing and Sales
organizations. Marketing professionals use them to collect, exchange, and analyze data
related to customer needs and product development cycles. Sales application includes
teleshopping, which uses order-entry computers or telephones connected to order
processing network, and online-reservation services for hotels, airlines and so on.

Financial services: Today's financial services are totally depended on computer networks.
Application includes credit history searches, foreign exchange and investment services, and
electronic fund transfer, which allow user to transfer money without going into a bank (an
automated teller machine is an example of electronic fund transfer, automatic pay-check is
another).

Manufacturing: Computer networks are used in many aspects of manufacturing including

manufacturing process itself. Two of them that use network to provide essential services
are computer-aided design (CAD) and computer-assisted manufacturing (CAM), both of
which allow multiple users to work on a project simultaneously.

Directory services: Directory services allow list of files to be stored in central location to
Speed worldwide search operations.

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Information services: A Network information service includes bulletin boards and data
banks. A World Wide Web site offering technical specification for a new product is an
information service.

Electronic data interchange (EDI): EDI allows business information, including documents
such as purchase orders and invoices, to be transferred without using paper.

Electronic mail: probably it's the most widely used computer network application.

Teleconferencing: Teleconferencing allows conference to occur without the participants

being in the same place. Applications include simple text conferencing (where participants
communicate through their normal keyboards and monitor) and video conferencing where
participants can even see as well as talk to other fellow participants. Different types of
equipments are used for video conferencing depending on what quality of the motion you
want to capture (whether you want just to see the face of other fellow Participants or do
you want to see the exact facial expression).

Voice over IP: Computer networks are also used to provide voice communication. This
kind of voice communication is pretty cheap as compared to the normal telephonic
conversation.

Video on demand: Future services provided by the cable television networks may include
video on request where a person can request for a particular movie or any clip at anytime
he wish to see.

There are two types of transmission technology that are in widespread use. They are as
follows:

1. Broadcast links.
2. Point-to-point links.

Broadcast networks have a single communication channel that is shared by all the
machines on the network. Short messages, called packets in certain contexts, sent by any
machine are received by all the others. An address field within the packet specifies the
intended recipient. Upon receiving a packet, a machine checks the address field. If the
packet is intended for the receiving machine, that machine processes the packet; if the
packet is intended for some other machine, it is just ignored.

Broadcast systems generally also allow the possibility of addressing a packet to all
destinations by using a special code in the address field. When a packet with this code is
transmitted, it is received and processed by every machine on the network. This mode of
operation is called broadcasting. Some broadcast systems also support transmission to a
subset of the machines, something known as multicasting. One possible scheme is to reserve
one bit to indicate multicasting. The remaining n - 1 address bits can hold a group number.
Each machine can ''subscribe'' to any or all of the groups. When a packet is sent to a
certain group, it is delivered to all machines subscribing to that group.

In contrast, point-to-point networks consist of many connections between individual pairs

of machines. To go from the source to the destination, a packet on this type of network may
have to first visit one or more intermediate machines. Often multiple routes, of different
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lengths, are possible, so finding good ones is important in point-to-point networks. As a
general rule (although there are many exceptions), smaller, geographically localized
networks tend to use broadcasting, whereas larger networks usually are point-to-point.
Point-to-point transmission with one sender and one receiver is sometimes called
unicasting.

LOCAL AREA NETWORKS

Local area networks, generally called LANs, are privately-owned networks within a single
building or campus of up to a few kilometers in size. They are widely used to connect
personal computers and workstations in company offices and factories to share resources
(e.g., printers) and exchange information. LANs are distinguished from other kinds of
networks by three characteristics:

(1) Their size, (2) their transmission technology, and (3) their topology.

LANs are restricted in size, which means that the worst-case transmission time is bounded
and known in advance. Knowing this bound makes it possible to use certain kinds of
designs that would not otherwise be possible. It also simplifies network management.

LANs may use a transmission technology consisting of a cable to which all the machines are
attached, like the telephone company party lines once used in rural areas. Traditional
LANs run at speeds of 10 Mbps to 100 Mbps, have low delay (microseconds or
nanoseconds), and make very few errors. Newer LANs operate at up to 10 Gbps. In this
book, we will adhere to tradition and measure line speeds in megabits/sec (1 Mbps is
1,000,000 bits/sec) and gigabits/sec (1 Gbps is 1,000,000,000 bits/sec).

METROPOLITAN AREA NETWORKS

A metropolitan area network, or MAN, covers a city. The best-known example of a MAN is
the cable television network available in many cities. This system grew from earlier
community antenna systems used in areas with poor over-the-air television reception. In
these early systems, a large antenna was placed on top of a nearby hill and signal was then
piped to the subscribers' houses.

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At first, these were locally-designed, ad hoc systems. Then companies began jumping into
the business, getting contracts from city governments to wire up an entire city. The next
step was television programming and even entire channels designed for cable only. Often
these channels were highly specialized, such as all news, all sports, all cooking, all
gardening, and so on. But from their inception until the late 1990s, they were intended for
television reception only.

WIDE AREA NETWORKS

A wide area network, or WAN, spans a large geographical area, often a country or
continent. It contains a collection of machines intended for running user (i.e., application)
programs. We will follow traditional usage and call these machines hosts. The hosts are
connected by a communication subnet, or just subnet for short. The hosts are owned by the
customers (e.g., people's personal computers), whereas the communication subnet is
typically owned and operated by a telephone company or Internet service provider. The
job of the subnet is to carry messages from host to host, just as the telephone system carries
words from speaker to listener. Separation of the pure communication aspects of the
network (the subnet) from the application aspects (the hosts), greatly simplifies the
complete network design.

INTERNET
A global computer network providing a variety of information and communication
facilities, consisting of interconnected networks using standardized communication
protocols

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