Unit 2

Network Hardware
Content
1. Network Topologies
2. Network Devices
a. NIC Cards
b. Hub
c. Switch
d. Bridges
e. Wireless access points
f. Router
g. Gateways
h. Modems
i. ISDN Terminal Adaptor
j. Repeaters,
3. Types of Networks

2.1 Network Topology

It defines physical or logical arrangement of links in network. Topology is physical layout
of computers, cables and other connected devices on a network. The term topology refers to the
way a network is laid out either physical or logically two or more devices connect to a link or more
links form a topology. The topology of a network is the geometric representation of the relationship
of all the links and linking devices (called node) to each other.
There are two types of topologies-
1. Physical Topology
2. Logical Topology
Physical topology
The complete physical structure of transmission media is called physical topology. This
refers to the layout of cabling, location of nodes and interconnection between the nodes and
cabling.

Logical Topology
The logical topology is refers to how data is actually transferred in a network. This represents the
way that data passes through the network from one device to another.
Selection Criteria for Topologies -
• Size (no. of nodes) of the system.
• Cost of the components and service required.
• Management of network.
• Architecture of network.
• Cable type.
• Expandability of the network.
• The desired performance and reliability of entire system. Different types of topologies are:
a. Bus Topology
b. Ring Topology
 c. Star Topology
d. Mesh Topology
e. Tree and Hybrid Topology
Bus topology
It is a multipoint. A physical bus topology network typically uses one long cable called
backbone (bus). Short-cables called drop-cables can be attached to the backbone with the help of
taps. A tap is a connector that either slices into the main cable or punctures the sheathing (covering)
of a cable to create a contact with the metallic core.
As a signal travels along the backbone, some of its energy is transformed into heat.
Therefore, it becomes weaker and weaker as it travels farther and farther. For this reason there is a
limit on the number of taps a bus can support and on the distance between those taps.

Working of Bus topology

Bus topology is often used when a network installation is small, simple or temporary. On a
typical bus network the cable is just one or more wires with no active electronics to amplify the
signal or pass it along from computer to computer this makes a bus a passive topology. When one
PC sends a signal up and down the wire, all PC’s on network receive the information as it is
broadcasting. But only one (the one with the address that matches the one enclosed in the message)
accepts the information the rest will not respond the message.
Only one PC at a time can send a message therefor number of PC’s attached to a bus
network can significantly affects the speed of the network. A PC must wait until the bus is free
before it can transmit. Otherwise the bandwidth will simply get waste.
Use of Terminator:
Another important issue in bus network is termination. Since the bus is a passive topology
the electronic signal from a transmitting computer is free to travel the entire length of cable without
termination whenever the signals reaches the end of the wire it bounces back and travels back up
the wire. When a signal travels back and forth along and exterminated bus it is called ringing. To
stop the signal from ringing you attach terminator at the both end of the segment. The terminator
absorbs the electrical energy and stop the reflections. Cable can’t be left unterminated in a bus
network.

E.g.: -(Ethernet) 10 base2 also known as thin net is an inexpensive network based on bus topology.
Advantages of bus topology
1. The bus is simple, reliable in very small network easy to use and easy to understand.
2. It is easy for installation-that is backbone cable can be laid along the most convenient path
that connects the nodes by drop cables of various length.
3. The bus requires less amount of cables to connect the computer together and is therefore
less expensive than other cabling arrangements.
 4. It is easy to extend- (by using BNC Barrel connector) two cables can be joined into one
longer cable with a BNC barrel connector making a longer cable and allowing more PC to
join the network.
5. A repeater can also be used to extend a bus- A repeater boosts the signal and allows it to
travel a longer distance.
6. If one node fails others are not affected.

Demerits of bus topology

1. In case of failure of the backbone cable, the whole network will be affected.
2. Heavy network traffic can slow a bus considerably because only one PC can transmit at any
time resulting in wasting a lot of bandwidth as they interrupt each other instead of
communicating. The problem can get worse when more PC’s are connected to a network.
3. Each barrel connector weakens the electrical signal and too many may prevent the signal
from being correctly received along the bus.
4. It is difficult to troubleshoot faults - as bus cable break or malfunctioning computer.
5. A cable break or loose connection also cause reflection and bring down the whole network
and causing all the network activity to stop.
6. Difficult for reconfiguration-E.g.: Adding new devices may therefore require modification
or replacement of the backbone.

Ring Topology
In Ring topology each node is connected to the two nearest nodes so the entire network
forms a circle. Rings are used in high performance network. A signal is passed along the ring in
one direction, from device to device, until it reaches its destination. Each device in the ring
incorporates a repeater. When a device receives a signal intended for another device, its
repeater regenerates the bits and passes them
along.

Working of ring topology

Every PC is connected to next computer in the ring and each transmits what it receives from the
previous PC. The message flows around the ring in one direction. Since each PC retransmits what it
receives a ring is an active network. There is no termination because there is no end to the ring.
Token Ring -
Some ring networks use token passing. Token is a short message. A token is passed around
the ring until a PC wishes to send information to another PC. That PC modifies the token adds an
electronic address and data and sends it around the ring. Each PC in sequence receives the token
and the information and passes them to the next PC until either the electronic address of computer
matches or the token returns to its origin the receiving PC returns a message to originator that the
message has been received. The sending PC than creates another token and begins transmitting the
token. The token is circulated until the station is ready to send.
E.g.: - FDDI is a fast fiber optic networks based on ring topology. FDDI (Fiber Distributed data
interface)

Advantages of ring topology

i. A ring is relatively easy to install and configure (for fix number of devices).
ii. Fault isolation is simplified- generally in a ring a signal is circulating at all time if any
device does not receive a signal within the specified period. It can issue an alarm. Alarm
alerts the network operator to the problem of its location.
iii. To add or delete a device requires moving only two connections.
iv. Time to send data is known: that is package delivery time is fixed and guaranteed
because every PC is given to the token. No one PC can monopolies network.
v. No data collisions.

Disadvantages of ring
1. A single node failure leads to the collapse of the full network.
2. Unidirectional traffic can be disadvantage in a simple ring. A break in the ring can disable
the entire network; using dual ring can solve the weakness.
3. Expansion to the network can cause network disruption
Star topology
Physical star topology uses a central device or controller with drop cables extending in all
direction. The devices are not directly linked to one another. Each network device is connected via
point-to-point link to central device called ‘HUB’ multipoint repeater or concentrator. The
controller acts as an exchange: If one device wants to send data to another, it sends the data to the
controller, which then relays the data to the other connected device.
When network expansion is expected and a greater reliability is expected then star topology is
needed.
Advantages of star topology
There are several advantages to a star topology.
i. Addition, Moving and deletion involves only one connection between that device and hub.
ii. When the capacity of central hub is exceeded you can replace it with one that has larger
number of ports to plug lines into new hub.
iii. The center of the star network is a good place to diagnose network faults, intelligent hub (the
hub with microprocessor) also provide for centralize monitoring and management of
network.
iv. Single PC failures do not necessarily bring down whole star network. The hubs can detect a
network fall and isolate the defected PC or network cable and allow the rest of the network to
continue operating.
v. You can use several cable types in the same network with a hub that can accommodate
multiple cable types.
Disadvantages of star topology
1. If the central hub fails the whole network fails to operate.
2. Many star networks requires a devices at the central point to rebroadcast or switched
network traffic.
3. It cost more to cable a star networks because all the network cables must be pulled to
one central point requiring more cable than other networking topologies.

Mesh topology
In a mesh topology every device has dedicated point-to-point link to every other device.
The term dedicated means that the link carries only between the two devices it connects. A fully
connected mesh network has n (n-1)/2 physical connections to link devices.
To accommodate that many links every device on the network must have (n-1) output ports
because each device requires an interface for every other on the network. Mesh topology are not
usually practical. In addition unless each station frequently sends signal to all the other stations and
excessive amount of network bandwidth is wasted.
 Mesh gets unmanageable beyond a very small number of devices. Most mesh topology
networks are not true mesh networks.

Mesh installation
Mesh topology N/w become more difficult to install as the no. of devices increases because
of the sheer quantity of connections that must be made. A true mesh topology of seven devices
would require 21 connections and six I/O ports.
Advantages:-
➢ The use of dedicated links guaranties that connections can carry its own data load. Thus
eliminating the traffic problem that can occur when links must be shared by multiple
devices.
➢ Mesh topology is Robust (strong) if one link becomes unusable. It doesn’t incapacitate the
entire n/w.
➢ Another advantage is privacy and security when every message sent travels along a
dedicated line only the intended recipients sees it. Physical boundaries prevent other users
from gaining access to message.
➢ Point to point link make fault identification and fault isolation easy. Traffic can be routed
to avoid links with respected problems. This facility enables the n/w manager to discover
the precise location of the fault and aids it finding its cause and solution.
➢ Extremely fault tolerant.
➢ It is more reliable compare to other topologies.
➢ In case of heavy traffic data can be routed around busy root.

Disadvantages
➢ As it involves a lot of connection. The total no. of physical links and the no. of I/O ports
require to connect will be more and hence is prohibitively expensive.
➢ Difficult to install and reconfigure specially as no. of devices increases.
➢ Hardware required to connect each device is highly expensive.
➢ The sheer bulk of the wiring can be greater than the available space (walls, ceiling and
floors) can accommodate. For these reasons a mesh topology is usually implemented in a
limited fashion.

Hybrid Topology
A network can be hybrid. For example, we can have a main star topology with each branch
connecting several stations in a bus topology as shown in Figure
Star Bus (Tree Topology)

Star bus topology combines the bus and the star linking several stars hubs together with the
bus trunk. If one computer fails, the hub can detect the fault and isolate the PC. If a hub fails PC
connected to it will not be able to communicate and the bus n/w will be broken into two segments
that can’t reach each other.

Star ring
This is also called as star wired ring. The n/w cables are laid out much like a star n/w but a
ring is implemented in the central hub outgoing hubs can be connected through the inner hubs
effectively extending a loop of the ring. E.g. Token ring is considered a star ring although its
topology is physical a start its function logically in a ring.

2.2 Network control devices

To expand a single network without breaking it into new pass or connecting it through
another different network. All networks require devices to provide connectivity and functionality.
Purpose of Using Network Devices.
⚫ Allow a greater number of nodes to be connected to the network.
⚫ Extend the distance over which a network can extend.
⚫ Localize traffic on the network.
⚫ Can merge existing networks.
⚫ Isolate network problems so that they can be diagnosed more easily.
Devices and the layers at which they operate

You can usually use one of the following devices.

➢ Connectors
➢ Hubs
➢ Repeaters
➢ Bridges
➢ Switches
➢ Routers
➢ Modem, etc.
1. Connectors:
Que. List the different types of connector used in communication? State its uses.
➢ To connect cable between two computers.
➢ Connectors are of different type such as –
1. Twisted Pair cable
2. Co-axial Cable
3. Fibre optic cable.
➢ Connectors are type such as-
1. Jacks
2. Plugs
3. Sockets and ports
Example:
⚫ RS232 and V35 for serial interface
⚫ RJ45 and BNC connectors for Ethernet.
⚫ SC or ST connectors for fibre optic

BNC Connector
(Bayonet Nut Coupling) A commonly used plug and socket for audio, video and networking
applications that provides a tight connection. This connector has a center pin connected to the center
cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the
tube locks the cable to any female connector. BNCs are used to connect a variety of different
coaxial cable types. After the plug is inserted, it is turned, causing pins in the socket to be pinched
into a locking groove on the plug.

RJ-11 (Registered Jack)

Standard telephone cable connectors, RJ-11 has 4 wires (and RJ-12 has 6 wires). RJ-11 is the
acronym for Registered Jack-11, a four- or six-wire connector primarily used to connect telephone
equipment.

F-Type
The F connector is a type of RF connector commonly used for cable and universally for satellite
television.

RJ-45 (Registered Jack)

The acronym for Registered Jack-45 is RJ-45. The RJ-45 connector is an eight-wire connector
that is commonly used to connect computers to a local area network (LAN), particularly Ethernet
LANs. Although they are slightly larger than the more commonly used RJ-11 connectors, RJ-45s
can be used to connect some types of telephone equipment.

ST (Straight Tip) and SC (Subscriber Connector or Standard Connector)

Fibre network segments always require two fibre cables: one for transmitting data, and one for
receiving. Each end of a fibre cable is fitted with a plug that can be inserted into a network adapter,
hub, or switch. In the North America, most cables use a square SC connector (Subscriber
Connector or Standard Connector) that slides and locks into place when inserted into a node or
connected to another fibre cable, Europeans use a round ST connector (Straight Tip) instead.

USB (Universal Serial Bus)

Universal Serial Bus, or USB, is a computer standard designed to eliminate the guesswork in
connecting peripherals to a PC. It is expected to replace serial and parallel ports. A single USB port
can be used to connect up to 127 peripheral devices, such as mice, modems, keyboards, digital
camera's, printers, scanners, MP3 players and many more. USB also supports Plug-and-Play
installation and hot plugging.
Repeaters
A repeater or regenerator is an electronic device that operates on only the physical layer of
the OSI MODEL. Signal that carry information within a network can travel a fix distance before
attenuation enlarges the integrity of data. A repeater installed on a link receives the signal before it
becomes too weak, and put the refresh copy back on the link.
A repeater allows us extending only the physical length of a network. The repeater does not
change the functionality of the network in any way. The two sections (segments) connected by the
repeater in fig are in reality one network. The repeater doesn’t have the intelligence to keep the
frame from passing to the right side when it is meant for a station on the left. The difference is that
with the repeater stations receives the true copy of the frame.

Fig. Repeater
Repeater as not an amplifier
An amplifier can’t discriminate between the intended signal and noise. It amplifies equally
everything fed into it. A repeater doesn’t amplify the signal. It regenerates it. When it receives a
weak end or corrupted signal it creates a copy bit at the original strength.
The location of the repeater on a link is vital. A repeater must replace so that a signal
reaches it before any noise changes the meaning of any of its bits. A little noise can alert the
precision of a bits voltage with losing its identity.

Que: Describe repeater? State situations under which it is necessary in network?

⚫ It connects two segments of the same network.
⚫ Types of Single port, multi-port repeaters.
 2. Hub
Que. What is hub? State how they are classified?

Networks using a Star topology require a central point for the devices to connect. Originally this
device was called a concentrator since it consolidated the cable runs from all network devices. The
basic form of concentrator is the hub.

As shown in Figure; the hub is a hardware device that contains multiple, independent ports that
match the cable type of the network. Most common hubs interconnect Category 3 or 5 twisted-pair
cable with RJ-45 ends, although Coax BNC and Fiber Optic BNC hubs also exist. The hub is
considered the least common denominator in device concentrators. Hubs offer an inexpensive
option for transporting data between devices, but hubs don't offer any form of intelligence. Hubs
can be active or passive.
Important Points
⚫ A hub is used as a central device.
⚫ Connects the computers in star topology.
⚫ Hubs are simple devices that direct data packets to all devices connected to the hub.
⚫ Hubs regenerate and retime network signals
⚫ hubs work at the OSI physical layer
⚫ They cannot filter network traffic.
⚫ They cannot determine best path
⚫ They are really multi-port repeaters

Fig. HUB
There are three main types of hub:
❖ Passive hub
A passive hub simply combines the signal of n/w segment. There is no signal
processing or regeneration because it does not boost the signal and in fact absorbs some of
the signal. A passive hub reduces by half the maximum, cabling distance permitted.
 E.g. If a segment normally allows a reliable transmission distance of 100 meters, the
distance between a passive hub and a device can be only 50m also with a passive HUB each
pc can receive the signal send from all the other pc’s connected to the hub.
❖ Active hub
These are like passive hub except that they have electronic component that regenerate or
amplify signal. Because of this the distance between devices can be increased. The main
drawback to some active hub, i.e. they amplify noise as well as signal depending on whether
they function as simple amplifies or an as signal regenerator. They are also much more
expensive than passive hubs function as repeaters (Create a duplicate copy of signal). They
are sometimes called multi- port repeaters.
❖ Intelligent hub
In addition to signal regenerations these hubs perform some n/w management and
intelligent path selection. A switching HUB chooses only the port of the device where the
signal leads to go rather than sending the signal along all paths. Many switching hubs can
choose which alternative path with be weakest and send the signal that way. One
disadvantage to this is that you can permanently connect all transmission media segments
because each segment will be used only when a signal is send to device using that segment.
3. Bridges
A bridge is used to join two network segments together, it allows computers on either
segment to access resources on the other. They can also be used to divide large networks into
smaller segments. Bridges have all the features of repeaters, but can have more nodes, and since the
network is divided, there is fewer computers competing for resources on each segment thus
improving network performance.

Bridges can also connect networks that run at different speeds, different topologies, or
different protocols. But they cannot, join an Ethernet segment with a Token Ring segment, because
these use different networking standards. Bridges operate at both the Physical Layer and the MAC
sub layer of the Data Link layer. Bridges read the MAC header of each frame to determine on
which side of the bridge the destination device is located, the bridge then repeats the transmission
to the segment where the device is located.

Fig. Bridge

Unlike the repeaters which simply passes on all the signals it receives a bridges selectively
determines the appropriate segment to which it should pass a signal. It does this by reading the
address of the entire signal it receives. The bridges read the physical location of the source and
destination computers from the addresses and store it to a table.

The process works like this

• For learning bridges receives all signals from both the segments.
• The bridge reads the address and discards (filters) all signals from segment1 that are address
to segment1 because they don’t need to cross the bridge.

The figure shows the messages or signals which do not need to cross the bridge (Message from
computer-A to Computer- D) and other half part shows the messages that needs to pass through the
bridge (Message from computer-A to Computer-G). Bridges also provide security through this
portioning of traffic. There are basic two types of bridges.
➢ Transparent bridges
Keeps a table of addresses in memory to determination where to send the data.
⚫ Also called learning bridges
⚫ Build a table of MAC addresses as frames arrive.
⚫ Ethernet networks use transparent bridge
⚫ Duties are : Filtering frames, forwarding and blocking

➢ Source routing bridge

Requires the entire rule to be included in the transmission and don’t rout packets intelligently.
IBM token ring n/w uses this type of bridges. If a segment on n/w is been used only 60% then
consider, using bridges will improve performance.
⚫ Used in Token Ring networks
⚫ Frame contains not only the source and destination address but also the
bridge addresses.
Reasons to go for bridges
➢ To divide the big n/w like university.
➢ Organization may geographically spread over multiple buildings.
➢ To split an n/w logical.
 ➢ Single LAN is adequate (sufficient but physical distance is too great).
➢ For reliability bridges can be placed at critical nodes. To prevent a single node go out of
order from bringing down the entire system. (E.g. bus topology)
➢ For security insert bridges at various places and being careful not to forward sensitive
traffic.

Advantages of using a bridge

– Extend physical network

– Reduce network traffic with minor segmentation
– Reduce collisions
– Connect different architecture

Disadvantages of using bridges

– Slower than repeaters due to filtering

– Do not filter broadcasts
– More expensive than repeaters
Switch
• On the surface, a switch looks much like a hub.
• Despite their similar appearance, switches are far more efficient than hubs and
are far more desirable for today’s network environments.
• Following Figure shows an example of a 32-port Ethernet switch.
• If you refer to it you’ll notice few differences in the appearance of the high-
density hub and this switch.

• a hub forwards data to all ports,

regardless of whether the data is planned for the system connected to the port.
• This arrangement is inefficient; however, it requires little intelligence on the
part of the hub, which is why hubs are inexpensive.
• Rather than forwarding data to all the connected ports, a switch forwards data
only to the port on which the destination system is connected.
• It looks at the Media Access Control (MAC) addresses of the devices
connected to it to determine the correct port.
• A MAC address is a unique number that is stamped into every NIC.
• By forwarding data only to the system to which the data is addressed, the
switch decreases the amount of traffic on each network link dramatically.
• In effect, the switch literally channels (or switches, if you prefer) data between
the ports.
Router
• Routers are an increasingly
common sight in any network
environment, from a small home
office that uses one to connect to an
Internet service provider (ISP) to a
corporate IT environment where
racks of routers manage data
communication with disparate
remote sites.
• Routers are network devices that
literally route data around the
network. By examining data as it
arrives, the router can determine the
destination address for the data;
then, by using tables of defined
routes, the router determines the
best way for the data to continue its
journey.
• Unlike bridges and switches, which use the hardware-configured MAC address
to determine the destination of the data, routers use the software-configured
network address to make decisions.
• This approach makes routers more functional than bridges or switches, and it
also makes them more complex because they have to work harder to determine
the information.
Working of Router:
• The basic requirement for a router is that it must have at least two network
interfaces.
• If they are LAN interfaces, the router can manage and route the information
between two LAN segments.
• More commonly, a router is used to provide connectivity across wide area
network (WAN) links.
• Figure shows a router with two LAN ports (marked AUI 0 and AUI 1) and two
WAN ports (marked Serial 0 and Serial 1).
• This router is capable of routing data between two LAN segments and two
WAN segments.
 • Gateway: The term gateway is applied to any device, system, or software
application that can perform the function of translating data from one format to
another.
• The key feature of a gateway is that it converts the format of the data, not the
data itself.
• Software gateways can be found everywhere.
• Many companies use an email system such as Microsoft Exchange or Novell
GroupWise.
• These systems transmit mail internally in a certain format. When email needs
to be sent across the Internet to users using a different email system, the email
must be converted to another format, usually to Simple Mail Transfer Protocol
(SMTP).
• This conversion process is performed by a software gateway.

Modem
• Modem is a contraction of the terms modulator and demodulator.
• Modems perform a simple function: They translate digital signals from a
computer into analog signals that can travel across conventional phone lines.
• The modem modulates the signal at the sending end and demodulates at the
receiving end.
• Modems are available as internal devices that plug into expansion slots in a
system; external devices that plug into serial or USB ports; PCMCIA cards
designed for use in laptops; and specialized devices designed for use in
systems such as handheld computers.
• In addition, many laptops now come with integrated modems. For large-scale
modem implementations, such as at an ISP, rack-mounted modems are also
available
ISDN Terminal Adaptor
• When the speed provided by a modem just isn’t enough, you must seek
alternatives.
• One of the speedier options available is an ISDN link.
• ISDN is a digital communication method that can be used over a conventional
phone line, although certain criteria must be met for an ISDN line to be
available (such as the availability of the service and the proximity of your
location to the telco’s site).
• To use ISDN, you need a device called an ISDN terminal adapter.
• ISDN terminal adapters are available as add-in expansion cards installed into
computers, external devices that connect to the serial interfaces of PC systems,
or modules in a router.
• An ISDN terminal adapter as a kind of digital modem. Remember that a
modem converts a signal from digital to analog and vice versa. An ISDN
terminal adapter translates the signal between two digital formats

a) An External ISDN Adaptor b) An Internal ISDN Adaptor

Wireless Access Points:
• Wireless access points, referred to as either WAPs or wireless APs, are a
transmitter and receiver (transceiver) device used for wireless LAN (WLAN)
radio signals.
• A WAP is typically a separate network device with a built-in antenna,
transmitter, and adapter.
• WAPs use the wireless infrastructure network mode to provide a connection
point between WLANs and a wired Ethernet LAN.
• WAPs also typically have several ports allowing a way to expand the network
 to support additional clients
• Depending on the size of the network, one or more WAPs may be required.
• Additional WAPs are used to allow access to more wireless clients and to
expand the range of the wireless network.
• Each WAP is limited by a transmissions range, the distance a client can be
from a WAP and still get a useable signal.
• The actual distance depends on the wireless standard being used and the
obstructions and environmental conditions between the client and the WAP

• WAP receives transmissions from wireless devices within a specific range and
transmits those signals to the network beyond.
• This network may be a private Ethernet network or the Internet.
• The transmission range a WAP can support and number of wireless devices
that can connect to it depends on the wireless standard being used and the
signal interference between the two devices.
• In infrastructure wireless networking, there may be multiple access points to
cover a large area or only a single access point for a small area such as a single
home or small building.
2.3 Types of Computer Networks
• There are various types of computer networks available. We can categorize
them according to their size as well as their purpose.
• The size of a network should be expressed by the geographic area and number
of computers, which are a part of their networks.
• It includes devices housed in a single room to millions of devices spread across
the world.
 PAN (Personal Area Network)
• PAN is a computer network formed around a person.
• It generally consists of a computer, mobile, or personal digital assistant.
• PAN can be used for establishing communication among these personal
devices for connecting to a digital network and the internet.

Characteristics of PAN
• It is mostly personal devices network equipped within a limited area.
• Allows you to handle the interconnection of IT devices at the surrounding of a
single user.
• PAN includes mobile devices, tablet, and laptop.
• It can be wirelessly connected to the internet called WPAN.
• Appliances use for PAN: cordless mice, keyboards, and Bluetooth systems.
Advantages
• PAN networks are relatively secure and safe
• It offers only short-range solution up to ten meters
• Strictly restricted to a small area
Disadvantages
• It may establish a bad connection to other networks at the same radio bands.
• Distance limits.
LAN(Local Area Network)
• A Local Area Network (LAN) is a group of
computer and peripheral devices which are
connected in a limited area such as school,
laboratory, home, and office building.
• It is a widely useful network for sharing
resources like files, printers, games, and other
application.
• The simplest type of LAN network is to connect
computers and a printer in someone's home or
office.
• In general, LAN will be used as one type of transmission medium.
• It is a network which consists of less than 5000 interconnected devices across
several buildings.
Characteristics of LAN
• It is a private network, so an outside regulatory body never controls it.
• LAN operates at a relatively higher speed compared to other WAN systems.
• There are various kinds of media access control methods like token ring and
ethernet.
Advantages of LAN
• Computer resources like hard-disks, DVD-ROM, and printers can share local
area networks. This significantly reduces the cost of hardware purchases.
• You can use the same software over the network instead of purchasing the
licensed software for each client in the network.
• Data of all network users can be stored on a single hard disk of the server
computer.
• You can easily transfer data and messages over networked computers.
• It will be easy to manage data at only one place, which makes data more
secure.
• Local Area Network offers the facility to share a single internet connection
among all the LAN users.
Disadvantages of LAN
• LAN will indeed save cost because of shared computer resources, but the
initial cost of installing Local Area Networks is quite high.
• The LAN admin can check personal data files of every LAN user, so it does
not offer good privacy.
• Unauthorized users can access critical data of an organization in case LAN
admin is not able to secure centralized data repository.
• Local Area Network requires a constant LAN administration as there are issues
related to software setup and hardware failures
WAN (Wide Area Network)

WA WA
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• WAN (Wide Area Network) is another important computer network that which
is spread across a large geographical area.
• WAN network system could be a connection of a LAN which connects with
other LAN's using telephone lines and radio waves.
• It is mostly limited to an enterprise or an organization.
Characteristics of WAN:
• The software files will be shared among all the users; therefore, all can access
to the latest files.
• Any organization can form its global integrated network using WAN.
Advantages of WAN
• WAN helps you to cover a larger geographical area. Therefore business offices
situated at longer distances can easily communicate.
• Contains devices like mobile phones, laptop, tablet, computers, gaming
 consoles, etc.
• WLAN connections work using radio transmitters and receivers built into
client devices.
Disadvantage of WAN
• The initial setup cost of investment is very high.
• It is difficult to maintain the WAN network. You need skilled technicians and
network administrators.
• There are more errors and issues because of the wide coverage and the use of
different technologies.
• It requires more time to resolve issues because of the involvement of multiple
wired and wireless technologies.
• Offers lower security compared to other types of networks.
MAN(Metropolitan Area Network)
• This is a network which is larger than a LAN but smaller than a WAN, and
incorporates elements of both. It typically spans a town or city and is owned by
a single person or company, such as a local council or a large company.

Characteristics of MAN
• It mostly covers towns and cities in a maximum 50 km range
• Mostly used medium is optical fibers, cables
• Data rates adequate for distributed computing applications.
Advantages of MAN
• It offers fast communication using high-speed carriers, like fiber optic cables.
• It provides excellent support for an extensive size network and greater access
to WANs.
• The dual bus in MAN network provides support to transmit data in both
directions concurrently.
• A MAN network mostly includes some areas of a city or an entire city.
Disadvantages of MAN
• You need more cable to establish MAN connection from one place to another.
• In MAN network it is tough to make the system secure from hackers
Other Types of Networks
• Apart from above mentioned here, are some other important types of networks:
• WLAN (Wireless Local Area Network)
• Storage Area Network
• System Area Network
• Home Area Network
• POLAN- Passive Optical LAN
• Enterprise private network
• Campus Area Network
• Virtual Area Network
Question Bank
• What is topology?
• Describe following.
• Bus topology with diagram and state it’s merits and demerits.
• Star topology with diagram and state it’s merits and demerits.
• Ring topology with diagram and state it’s merits and demerits.
• Mesh topology with diagram and state it’s merits and demerits.
• Describe Types of Networks (LAN / WAN/ MAN/ PAN)
• What is (NIC Card/HUB / Switch/ Bridge/ WAP/ Router/ Gateway/ Modem/
ISDN Terminal Adaptor/ Repeaters) Explain it in brief