Download Introduction Networking involves connecting computers and other

Introduction
Networking involves connecting computers and other electronic devices for the purpose of
sharing information and resources and for communication. Even though the concept of
networking is basic, a great deal of technology is required for one device to connect and
communicate with another, and many choices for physical connections and related software
are possible.
Network media
The most elementary network consists of two computers connected by some kind of
transmission medium, such as wire, cable, or air waves, to transmit data from one machine
to the other. No matter how many computers are interlinked or what kind of connection is
used, all networking derives from this basic description. In fact, when computers
communicate, they do so most frequently in pairs—one machine sends information and the
other receives that information. Of course, most networks consist of many computers and
are usually connected by a networking device, such as a hub, switch, or access point.
The primary motivation for networking is the need for people to share data and to
communicate quickly and efficiently.
Most businesses today use networks to store and share access to all kinds of data and
applications and to provide communications for employees and business partners. For these
reasons, networks are regarded as critical business tools. Nearly all users in today's
workplace use computers to connect to their company networks.
Personal computers alone are valuable business tools, but without a network, computers are
isolated and can neither share data with other computers nor access network nor attached
peripheral devices, such as printers, scanners, and fax machines.
The following uses represent some of the primary advantages of networking:
■ there is data sharing which enables groups of users to exchange information and route
data from one user to another as workflow demands. Data sharing also usually means that
master copies of data files reside in a specific place on another computer elsewhere on the
network, and users can access the master copy to do their work. When multiple users access
the same file simultaneously, their software must be able to merge updates to keep a single
master copy consistent and correct.
■ because data sharing makes it possible to circulate messages, documents, and other files
among users, it can also improve human communication substantially. Although no
company installs a network simply to support electronic mail (e-mail), e-mail remains the
most popular networked application in most organizations because it makes communication
so easy and efficient.
■ Peripheral device sharing enables groups of users to take advantage of peripherals, such
as printers, scanners, fax machines, and other devices attached directly to a network or to a
generally available computer attached to a network. Companies can, therefore, buy fewer
peripherals but spend more on each one so that better features and higher levels of service
are widely available. For many businesses, this capability alone justifies the costs and
efforts of networking.
A small network, limited to a single collection of machines and one or more cables and
other peripheral equipment, can be called a local area network (LAN). LANs also form the
basic building blocks for constructing larger networks called internetworks. An
internetwork is a network of networks or a networked collection of LANs tied together by
devices such as routers. For large organizations that occupy more than one floor in an
office building or operate in multiple buildings in a campus setting. When the number of
computers exceeds 100 and the distance to be spanned is more than 1000 feet, an internetwork is usually needed. The Internet, the best example of the largest internetwork in the
world, is a vast public wide area internetwork that makes it possible for any computer in the
world to communicate with any other computer in the world using standard technologies
and protocols.
Because of their limitations, early LANs were unable to meet the networking requirements
of large organizations, especially those that operated in multiple locations. The benefits of
networking were so great, however, that technology evolved to accommodate larger,
geographically dispersed organizations. As the scope of a network expands to encompass
multiple groups of users in multiple locations, LANs can grow into wide area networks
(WANs). A WAN is an internetwork that spans distances measured in miles and links two
or more separate LANs. WANs use the services of third-party communications providers,
such as telephone companies, to carry network traffic from one location to another.
Occasionally, you might encounter a network type called a metropolitan area network
(MAN). Essentially, MANs use WAN technologies to interconnect LANs in a specific
geographic region, such as a city. It's not uncommon to find large, complex networks
involving all three network types: LANs for purely local access, MANs for regional or
citywide access and WANs for access to remote sites elsewhere in the country or around the
world.
Network architecture.
Fundamentally, there are two network architectures namely client-server and peer-peer. Any
computer on a network plays one of two basic roles: a client or a server. A server is a
computer that shares its resources across the network, and a client is one that accesses
shared resources. Client requests information and a server respond by providing the
requested information or by denying the request.
In client/server networking environments, certain computers take specialized roles and
function mainly as servers, and ordinary users' machines tend to function mainly as clients.
In other networking environments, computers can function as clients or servers, as
circumstances dictate. For example, a computer can act as a server and provide resources to
other machines, or it can request a resource from another computer, thereby acting as a
client to that machine. Because all machines on this type of network function at more or less
the same level of capability, these machines are called peers. By extension, this type of
networking peers share and request resources from one another. Typical examples include
Vista, XP, and 2000 Professional operating systems; they operate in peer-to-peer
networking environments.
Peer-to-peer networks are uniquely well suited to small organizations, which tend to have
small networks and small operating budgets. Peer-to-peer networks are also easy to use and
don't require extensive staff training or a dedicated cadre of network administrators. With
no centralized control, the loss of a single machine means only the loss of access to the
resources on it; otherwise, a peer-to-peer network continues to function when one computer
fails. For small businesses, peer-to-peer networks can be an inexpensive, easy, and
convenient way to take advantage of the increased productivity and communications that
networks provide.
Peer-to-Peer Networking Advantages include:
 A peer-to-peer network is easy to install and configure.
 Machines don't depend on the presence of a dedicated server.
 Users control their own shared resources.
 Peer-to-peer networking is inexpensive to purchase and operate.
 Peer-to-peer networks need no additional equipment or software beyond a suitable
operating system.
 No dedicated administrators are needed to run the network.
 A peer-to-peer network works best for networks with 10 or fewer users.
Peer-to-Peer Networking Disadvantages include:
 Network security applies to only a single resource at a time.
 Users might be forced to use as many passwords as there are shared resources.
 Each machine must be backed up to protect all shared data.
 Every time a user accesses a shared resource, performance of the machine where the
resource resides is reduced.
 There is no centralized organizational scheme to locate or control access to data.
 Access to a shared resource is unavailable if the machine where the resource resides
is turned off or crashes.
 A peer-to-peer network doesn't usually work well with more than 10 users.
Server-Based Networks
Server-based networks can be also referred to as client/server. A server is best described as
a machine with the sole function of responding to client requests. A server is seldom
operated by someone sitting in front of it (and then usually only for installation,
configuration, or management tasks); therefore, a server's main role on a network is to be
continuously available to handle the many requests for its services that a community of
clients can generate.
Server-based networks provide centralized control over network resources, primarily by
instituting network security and control through the server's operating system configuration
and setup. The computers used for servers usually have faster CPUs, more memory, larger
disk drives, and extra peripherals compared to user machines.
Server-based networks' centralization of resources and control has both negative and
positive consequences. Although centralization simplifies access, coordinates control, and
aggregates resources, it can also introduce a single point of failure on networks. Without an
operational server, a server-based network is no network at all. On networks with more than
one server, loss of a single server means loss of all resources associated with that server. In
addition, if that lost server is the only source of access control information for a set of users,
those users can't access the network either.
Server-Based Networking Advantages include:

Centralized user accounts, security, and access controls simplify network
administration.
 More powerful equipment means more efficient access to network resources.
 Server hardware design is generally more robust, providing features such as faulttolerant hardware and redundant systems.

A single password for network logon delivers access to network-wide resources as
specified in access controls.
 Server-based networking makes the most sense for networks with 10 or more users
or any networks where resources are used heavily.
Server-Based Networking Advantages include:
The following list summarizes the disadvantages of server-based networking:
 At the worst, server failure renders a network unusable; at the least, it results in loss
of network resources.
Complex server software requires allocating expert staff, which increases expenses.
 Dedicated hardware and specialized software add to the cost of server-based
networking.
Network Topology
Network Topology or configuration refers to the layout of connected devices on the
network. Physical topology describes how the network physically looks or how the network
is physically designed. While logical topology describes how data is transmitted through the
network.
The following are examples of topologies which are available:
Bus network topology
A bus network is a network architecture in which a set of clients are connected via a shared
communication line called a bus.
It uses a linear segment of cable to connect all network devices.
Devices typically connect to the bus (the cable) through connectors. At each end of the bus
are terminators. Each terminator absorbs the signal when it reaches the end of the cable.
Without a terminator, a signal would bounce back and cause network errors. In a logical bus
topology, only one transmission can occur at any given moment. Otherwise, two
transmissions would collide and cause network errors. Termination ensures that the signal is
removed from the cable when it reaches either end, preventing possible network errors.
Advantages of Bus network
 They are easy to implement and extend.
 They are well suited for temporary networks.
 Typically it’s the cheapest topology to implement.
 Failure of one station on the network does not affect other stations.
Disadvantages of Bus network
 They are difficult to administer/ troubleshoot if devices are many
 There is always limited cable length and number of stations
 A cable break in the bus can disable the entire network
 The maintenance costs may be higher in the long run
 Performance degrades as additional computers are added to the bus or on heavy
traffic.
 Mainly it is low in security, for instance one virus in the network can affect all
stations on a network.
 Proper termination is required (loop must be in closed path)
Ring network
A ring network is a topology of computer networks where each node is connected to two
other nodes, so as to create a ring. The most popular example is a token ring network.
In other words, I can say physically, a ring topology is shaped in a ring. Cables pass from
computer to computer until the ring is complete. When data is transmitted, each workstation
receives the signal and then passes it on. Logically, a ring topology works by passing the
signal from one node to another until it reaches all the way around the ring.
Ring networks tend to be inefficient when compared to star networks because data must
travel through more points before reaching its destination.
Advantages of Ring network
 All stations on a ring have equal access to resources
 Each node on the ring acts as a repeater, allowing networks to span greater distances
than other topologies.
 Because data travels in one direction high speeds of transmission of data are
possible.
 When using a coaxial cable to create a ring network the service becomes much
faster.
Disadvantages of Ring network
 Often they are the most expensive topology to implement.
 If there is a break in the cable of a physical ring topology, the network becomes
unavailable.
 Damage to the ring will affect the whole network
 Often quite difficult to troubleshoot and reconfigure
Star network
Physically, the star looks like a star and the simplest form of a star network consists of one
central device switch or/ hub and all other stations attached to it.
Advantages of Star network
 They are easy to implement and to extend, even in large networks.
 They are also well suited for temporary network.
 The failure of a non-central node will not have major effects on the functionality of
the network.
 It has been reliable market proven system.
 No problem with collisions of data since each station has its own cable to
server/hub.
 Security can be implemented in the hubs/switch.
Disadvantages of Star network
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Maintenance costs may be higher in the long run.
Failure of the central device can disable the entire network.
One virus in the network can affect all the stations.
Depending on the transmission media, length limitation may be imposed from the
central location used.
Mesh network
A mesh network topology is the most fault tolerant but the most expensive. It connects each
device in a network to every other device in the network creating a mesh. Any single cable
or device failure in a mesh configuration does not affect the network performance
Communication concepts
The basic data communication system consists of three parts.
Sender
Medium
Destination
1. The sender (source) who creates the message or data to be transmitted
2. A medium is the communication stream through which data is being transmitted.
3. The Destination is the receiver of the data transmitted.
In data communication four basic terms are frequently used and they include:
Data: A collection of facts in raw forms that become information after processing.
Signals: Electric or electromagnetic encoding of data.
Signaling: Propagation of signals across a communication medium.
Transmission: Communication of data achieved by the processing of signals.
Data Transmission Modes
There are three ways for transmitting data from one point to another.
1. Simplex: In simplex mode the communication can take place in one direction. The
receiver receives the signal from the transmitting device. In this mode the flow of
information is uni-directional. Hence it is rarely used for data communication. Example
include text messages which scrolls on television screen
2. Half-duplex: In half-duplex mode the communication channel is used in both directions,
but only in one direction at a time. Thus a half-duplex line can alternately send and receive
data. Example can be a communication using the walkie- talkie.
3. Full-duplex: In full duplex the communication channel is used in both directions at the
same time. Use of full-duplex line improves the efficiency as the line turnaround time
required in half-duplex arrangement is eliminated. Example of this mode of transmission is
the telephone
Communication Media
They facilitate the transmission of a signal from one device to another, and the
include:
1. Wire Pairs: Wire pairs are commonly used in local telephone communication and for
short distance digital data communication. They are usually made up of copper and the pair
of wires is twisted together. Data transmission speed is normally 9600 bits per second in a
distance of 100 meter. It is relatively inexpensive, widely available, easy to work with, can be
run through the wall. Some of the disadvantages include; it emits electromagnetic interferences,
its relatively slow, subjected to interferences from electrical sources, and can be easily be
tapped. The twisted pairs use RJ 45.
Fig 21
Major types of twisted pairs include the shielded and unshielded
2. Coaxial Cables: Coaxial cable is groups of specially wrapped and insulated wires that
are able to transfer data at higher rate. They consist of a central copper wire surrounded by
an insulation over which copper mesh is placed. They are used for long distance telephone
lines and local area network for their noise immunity and faster data transfer. The speed is
coated above 100 Mbps. The cable is free from interference and has a higher bandwidth, used
for cable television.
3. Microwave: Microwave system uses very high frequency radio signals to transmit data
through space. The transmitter and receiver of a microwave system should be in line-ofsight because the radio signal cannot bend. With microwave very long distance transmission
is not possible. In order to overcome the problems, amplification of weak signal by
repeaters are used at intervals of 25 to 30 kilometers between the transmitting and receiving
end.
4. Satellite Communication: are typically used for communication in large geographically dispersed
areas to overcome difficulties with cabling media or terrestrial microwaves.
In satellite communication, microwave signal is transmitted from a transmitter on earth to
the satellite at space. The satellite amplifies the weak signal and re-transmits it back to
ground station receivers. In microwave the data transmission rate is 16 G bits per second.
They are mostly used to link big metropolitan cities.
Advantages

Cost of transmission is the same regardless of distance or number of stations
receiving.
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High band width

Carry signals across political boundaries with less government regulations

Cover a wider area as opposed to cable media and microwave terrestrial.

Users can be highly mobile while sending and receiving signals.
Disadvantages.
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There’s propagation delay approximately one quarter of a second.
The signals can easily be tapped.
Some frequencies used are susceptible to interferences from bad weather or
electrical based signals.
Conclusion
In conclusion I can say that communication technology is perhaps the most significant
change agent in the world today, as it has helped to create a world in which national
borders, geographic distances, and physical limitations become less relevant, and present
ever-diminishing obstacles. The creation of networks for the exchange of ideas and
information has the potential to increase productivity opportunities across the globe. As the
networks connects people and promotes unfettered communication, it presents the platform
on which to run businesses, to address emergencies, to inform individuals, and to support
education, science, and government. I can say the methods that we use to share ideas and
information are constantly changing and evolving.
Early data networks were limited to exchanging character-based information between
connected computer systems. Current networks have evolved to carry voice, video streams,
text, and graphics between many different types of devices. This platform provides access to
a wide range of alternative and new communication methods that enable people to interact
directly with each other almost instantaneously.