In the star topology, all computers and other network devices connect to a central device called a hub or switch. Each connected device requires a single cable to be connected to the hub, creating a point-to-point connection between the device and the hub.Using a separate cable to connect to the hub allows the network to be expanded without disruption to the network. A break in any single cable will not cause the entire network to fail
By: Rohit kumar
BBS 2nd year
A resource, or system resource, is any physical or
virtual component of limited availability within a
computer system. Every device connected to a computer
system is a resource. A network refers to an
interconnected or interrelated chain, group, or system.
Network resources therefore, refer to communication
media and network support that are essential for
information systems in all types of business
Telecommunication is the exchange of information in any form i.e.,
voice, data, text, images, audio, video, etc. over networks. Basic
components of telecommunications networks include:
1) Terminals: any input/output device that uses telecommunications
network to transmit or receive data. Ex: networked computers,
networked personal computers, etc.
2) Telecommunications processors: These are specialized hardware
components that support data transmission and reception
between terminals and computers. Ex: modem, switches and
3) Telecommunications channels: refer to channels over which data
is transmitted and received using combinations of media such as
copper wires, coaxial cables, fiber optic cables, or wireless systems
like microwave carriers, etc.
4. Computers : All sizes and types of computers can be
connected to telecommunications networks. Ex:
Typical arrangement includes mainframe computer as
a host for the network, a minicomputer as a front-end
processor, with a dedicated microcomputer as a
network server to a smaller local group of networked
5. Telecommunications control software: consists of
programs that control telecommunications activities
and manage the functions of telecommunications
For ex: network management programs include:
Telecommunications monitors (mainframes)
Network operating systems (network servers)
Web browsers (microcomputers)
Structure of a telecommunications network
Channels and Media
There are many different types of networks that serve as the
telecommunications infrastructure for the internet and the
intranets and extranets of inter-networked enterprises.
However there are some basic types of networks, such as:
Telecommunication networks that covers a large
geographic area are called WANs. They are essential for
the working of many business and govt. organizations
and their end users. For ex: WANs are used by many
multinational companies to transmit and receive
information among their employees, customers, suppliers
and other organizations across cities, regions and
Connects computers within a limited physical area, such as
an office, classroom, or building. LANs have become
commonplace in organizations as the link end users in
offices, departments etc. They use a variety of media such
as, telephone wiring, wireless radio and infrared systems to
interconnect microcomputer workstations and computer
peripherals enabling distribution of data files and software
packages along the network. To communicate each PC has
a circuit board called network interface card.
Many organizations use VPN to establish secure intranets
VPN relies on network firewalls, encryption, and other
security features to build a “pipe” through the Internet that
enables to send and receive data.
•Creates a private network without the high cost of a
separate proprietary connection.
•Safe exchange of files between distant branches without
risk of anyone else outside the pipe seeing it.
In a client/server network, end user personal computers or
networked computers workstations are the clients. They are
interconnected by local area networks and Network servers
manage the networks. It is also called a two-tier client
server model because it interconnects LANs and WANs.
Today, Larger computer systems are being replaced with
multiple client/server networks. This involves a complex and
costly effort to install new application software that replaces
the software of older mainframe-based business information
Client/server networks are more adaptable to a diverse range
of business needs & computing workload.
With growing reliance on computers, for many users, the
network is the computer. This network computing concept
views networks as the central computing resource of any
organization. In network computing, network computers and
other Thin clients provide a browser-based user interface for
processing applets. Thin clients include Network computers,
Net PCs & Other low-cost network devices or information
appliances. It is called three-tier client/server model as it
consists of thin clients, application servers and database
Peer-to-peer networks are a powerful telecommunications
networking tool for many business applications. It has two major
1) Central Server Architecture: P2P file-sharing software
connects all PCs to a central server that contains a
directory of all the other users in the network.
When a PC requests a file, the server searches for any user
who has that file and is online at that time.
Then The server sends the requesting PC a list of links to
all such active users.
Clicking on one such link connects the two PCs and
automatically transfers the file to the hard drive of
2) Pure Peer-to-Peer Architecture: There is no central
directory or server. First, the File sharing software
connects your PC to one of the online users in the
network. Then an active link to your username is
transmitted to all the online users in the network that
first user encountered in previous sessions. In this way
the more you use peer to peer the more the active links
When you request a file, the software searches every
online user and sends you a list of active file names.
Clicking a link automatically transfers the file from
that user’s hard drive to yours.
1)Wired technologies include twisted pair wires, coaxial
cables, and fiber-optic cables, all of which physically link the
devices in a network.
2)Wireless technologies include terrestrial microwave,
communication satellites, cellular phone systems, and packet
and LAN radio, all of which use microwave and other radio
•Consists of Cu wire twisted into pairs
•Wrapped or shielded in a variety of forms
•Used in established communications for both
voice and data transmission
•Used extensively in home and office telephone
systems and many local area networks
•Transmission speeds range from
2mbps(unshielded) to 100mbps(shielded).
Consists of a sturdy Cu or Al wire wrapped with spacers to
insulate and protect it
Insulation minimizes interference and distortion of the
signal it carries
Can be placed underground and laid on the floors of lakes
Transmission speeds range from 200-500 mbps
Used for cable T.V. systems, short distance computer
•Consists of one or more hair-thin filaments of glass fiber
wrapped in a protective jacket.
•Conduct pulses of visible light elements at transmission
rates as high as Tbps
•Provide substantial size and weight reductions
•Multiple fibers can be placed in the same cable
Involves earthbound microwave systems that
transmit high speed radio signals between relay
stations spaced approx 30 miles apart
Usually placed on top of buildings, towers, hills,
and mountain peaks
Use microwave radio as their telecommunication
HEO communications satellites are placed in stationary
geosynchronous orbits approximately 22,000 miles
above the equator
Powered by solar panels and transmission speeds range
in several hundred Mbps
Serve as relay stations transmitted from earth stations
and use dish antennas to beam microwave signals to
Used for voice and video transmission of large volumes
Many Cos use networks of small dish antennas known
as VSAT to connect their stores and distant worksites via
Its use arrives when wiring an office/building for a
local area network is often a difficult and costly task
Growing rapidly because of high speed technologies
Prime example is Wi-Fi which is faster and less
expensive than other technologies
Wi-Fi wireless LANs enable laptop PCs and other
devices to connect easily to internet
Short range wireless technology rapidly being built into
computer and other devices
Serves as a cable-free wireless connection to peripheral
Operates at 1Mbps with a range of 10 to 100m
Cable replacement technology
Smart telephones, pagers, PDAs, other portable
devices have become very thin clients in wireless
Agreement on standard WAP has encouraged the
development of many wireless web services
Telecommunications industry’s goal is to raise
wireless transmission speeds to enable streaming
video and multimedia apps on mobile devices
Telecommunications processors such as modems,
multiplexers, and other devices perform a variety
of support functions between the terminals and
computers in a telecommunications network. Let's
take a look at some of these devices and their
Modems. Modems are the most common type of communications
processor. They convert the digital signals from a computer or
transmission terminal at one end of a communications link into analog
frequencies, which can be transmitted over ordinary telephone lines.
A modem at the other end of the communications line converts the
transmitted data back into digital form at a receiving terminal. This
process is known as modulation and demodulation, and the word
modem is a combined abbreviation of those two words.
Modems are used because ordinary telephone networks were primarily
designed to handle continuous analog signals (electromagnetic
frequencies), such as those generated by the human, voice over the
Since data from computers are in digital form
(voltage pulses), devices are necessary to
convert digital signals into appropriate analog
transmission frequencies and vice versa.
However, digital communications networks
that transmit only digital signals and do not
need analog/digital conversion are becoming
commonplace. Since most modems also
perform a variety of telecommunications
support functions, modems may still be needed
in digital networks.
Telecommunications network are interconnected by
special purpose communications processors called
inter-network processors, which include switches,
routers, hubs, and gateways.
Switches-A switch is a communications processor that
makes connections between telecommunications
circuits in a network. Switches are now available in
managed versions with network management
Bridge-A bridge is a device that connects two or more
local area networks that use the same communication
rules or protocol.
Router-A router is an intelligent communication
processor that interconnects networks based on
different rules or protocols, so a telecommunication
message can be routed to its destination.
Hub-A hub is a port switching communications
processor. Advanced versions of hubs provide
automatic switching among connections called ports
for shares access to a network's resources.
Gateway-Networks that use different communications
architectures are interconnected by using a
communications processor called a gateway.
All these devices are essential to providing
connectivity and easy access between the multiple
LANs within an organization and the wide area
networks communications channel. In many cases,
star networks take the form of hierarchical networks.
Multiplexers. A multiplexer is a communications processor that allows
a single communications channel to carry simultaneous data
transmissions from many terminals. Thus, a single communications
line can be shared by several terminals.
Typically, a multiplexer merges the transmissions of several terminals
at one end of a communications channel, while a similar unit separates
the individual transmissions at the receiving end.
This is accomplished in two basic ways. In frequency division
multiplexing (FDM), a multiplexer effectively divides a high-speed
channel into multiple slow speed channels. In time division
multiplexing (TDM), the multiplexer divides the time each terminal
can use high-speed line into very short time slots, or time frames.
A network topology describes the arrangement of
systems on a computer network.
It defines how the computers, or nodes, within the
network are arranged and connected to each other.
Easy to implement
Limits on cable length and Workstation
Low Cost Difficult to isolate network faults
A cable fault affects all workstations
As the number of workstations increase,
the speed of the network slows down
In bus network The computers that send data also attach address of the
destination computer with the data.
All computers connected to the bus receive the data but only that computer accept it
whose address matches the address attached with data.
In this topology only one computer at a time can send a data therefore the speed of
network reduces as the number of computers attached to the bus increases.
In the star topology, all computers and other network
devices connect to a central device called a hub or switch.
Each connected device requires a single cable to be connected to the hub,
creating a point-to-point connection between the device and the hub.
Using a separate cable to connect to the hub allows the network to be expanded
without disruption to the network. A break in any single cable will not cause the
entire network to fail
Easy to add new workstations
Hub failure cripples all workstations
connected to that hub
Hubs are slighty more expensive than thin-
Centralized network/hub monitoring
Cable failures affect limited users Costly Wiring
Equal access for all users Difficult Connections
Each workstation has full access
speed to the ring
Expensive Adaptor Cards
As workstation numbers increase
performance diminishes slightly
the ring topology is a computer network configuration where each
network computer and device are connected to each other forming a large circle (or
Each packet is sent around the ring until it reaches its final destination. Today, the
ring topology is seldom used.