200280116023 Bhavik

LD College of Engineering
Ahmedabad- 380015

Computer Network
Practical- 1
Study of different Network devices

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Network devices
Network devices, or networking hardware, are physical devices that
are required for communication and interaction between hardware
on a computer network.
There are several types of network devices which are demonstrated
below one by one.

1. Hub

A hub is a physical layer networking device which is used to connect

multiple devices in a network. They are generally used to connect
computers in a LAN. A hub has many ports in it. A computer
which intends to be connected to the network is plugged in to one of
these ports.
Hubs connect multiple computer networking devices together. A hub
also acts as a repeater in that it amplifies signals that deteriorate after
traveling long distances over connecting cables. A hub is the simplest
in the family of network connecting devices because it connects LAN
components with identical protocols.

A hub can be used with both digital and analoge data, provided its
settings have been configured to prepare for the formatting of the
incoming data. For example, if the incoming data is in digital
format,the hub must pass it on as packets; however, if the incoming
data is analog, then the hub passes it on in signal form.

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Hubs do not perform packet filtering or addressing functions; they just
send data packets to all connected devices. Hubs operate at the
Physical layer of the Open Systems Interconnection (OSI) model. There
are two types of hubs: simple and multiple port.
Features of Hubs

 A hub operates in the physical layer of the OSI model.

 A hub cannot filter data. It is a non-intelligent network device that sends
message to all ports.
 It primarily broadcasts messages. So, the collision domain of all nodes
connected through the hub stays one.
 Transmission mode is half duplex.
 Collisions may occurs during setup of transmission when more than one
computers place data simultaneously in the corresponding ports.
 Since they lack intelligence to compute best path for transmission of data
packets, inefficiencies and wastage occur.
 They are passive devices, they don’t have any software associated with it.
 They generally have fewer ports of 4/12.
Types of Hub:

 Passive Hubs − Passive hubs connects nodes in a star configuration by

collecting wiring from nodes. They broadcast signals onto the network
without amplifying or regenerating them. As they cannot extend the
distance between nodes, they limit the size of the LAN.
 Active Hubs − Active hubs amplify and regenerate the incoming
electrical signals before broadcasting them. They have their own
power supply and serves both as a repeater as well as connecting
centre. Due to their regenerating capabilities, they can extend
the maximum distance between nodes, thus increasing the size
of LAN.
 Intelligent Hubs − Intelligent hubs are active hubs that provide
additional network management facilities. They can perform a
variety of functions of more intelligent network devices like

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network management, switching, providing flexible data rates
etc.

2. Switch:

Switches are networking devices operating at layer 2 or a data link

layer of the OSI model. They connect devices in a network and use
packet switching to send, receive or forward data packets or data
frames over the network.
A switch has many ports, to which computers are plugged in. When
a data frame arrives at any port of a network switch, it examines
the destination address, performs necessary checks and sends the
frame to the corresponding device(s).It supports unicast, multicast
as well as broadcast communications.

Features of Switches
 A switch operates in the layer 2, i.e. data link layer of the OSI
model.
 It is an intelligent network device that can be conceived as a
multiport network bridge.
 It uses MAC addresses (addresses of medium access control
sublayer) to send data packets to selected destination ports.
 It uses packet switching technique to receive and forward data
packets from the source to the destination device.
 It is supports unicast (one-to-one), multicast (one-to-many) and

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broadcast (one-to-all) communications.
 Transmission mode is full duplex, i.e. communication in the
channel occurs in both the directions at the same time. Due to
this, collisions do not occur.
 Switches are active devices, equipped with network software and
network management capabilities.
 Switches can perform some error checking before forwarding
data to the destined port.
 The number of ports is higher – 24/48.

Types of Switches
There are variety of switches that can be broadly categorised into 4
types −

Unmanaged Switch − These are inexpensive switches commonly

used in home networks and small businesses. They can be set up
by simply plugging in to the network, after which they instantly
start operating. When more devices needs to be added, more
switches are simply added by this plug and play method. They
are referred to as u managed since they do not require to be
configured or monitored.
 Managed Switch −These are costly switches that are used in
organisations with large and complex networks, since they can
be customized to augment the functionalities of a standard
switch. The augmented features may be QoS (Quality of Service)
like higher security levels, better precision control and complete
network management. Despite their cost, they are preferred in
growing organizations due to their scalability and flexibility.
Simple Network Management Protocol (SNMP) is used for
configuring managed switches.
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 LAN Switch − Local Area Network (LAN) switches connects
devices in the internal LAN of an organization. They are also
referred as Ethernet switches or data switches. These switches
are particularly helpful in reducing network congestion or
bottlenecks. They allocate bandwidth in a manner so that there is
no overlapping of data packets in a network.
 PoE Switch − Power over Ethernet (PoE) switches are used in PoE
Gigabit Ethernets. PoE technology combine data and power
transmission over the same cable so that devices connected to it
can receive both electricity as well as data over the same line.
PoE switches offer greater flexibility and simplifies the cabling
connections

3. Router:

A router is a networking device that forwards data packets

between computer networks. Routers perform the traffic directing
functions on the Internet. Then, using information in its routing
table or routing policy, it directs the packet to the next
network on its journey.
Routers are networking devices operating at layer 3 or a network
layer of the OSI model. They are responsible for receiving,
analysing, and forwarding data packets among the connected
computer networks. When a data packet arrives, the router
inspects the destination address, consults its routing tables to
decide the optimal route and then transfers the packet along this
route.

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Features of Routers
 A router is a layer 3 or network layer device.
 It connects different networks together and sends data packets
from one network to another.
 A router can be used both in LANs (Local Area Networks) and
WANs (Wide Area Networks).
 It transfers data in the form of IP packets. In order to transmit
data, it uses IP address mentioned in the destination field of the
IP packet.
 Routers have a routing table in it that is refreshed periodically
according to the changes in the network. In order to transmit
data packets, it consults the table and uses a routing protocol.
 In order to prepare or refresh the routing table, routers share
information among each other.
 Routers provide protection against broadcast storms.
 Routers are more expensive than other networking devices like
hubs, bridges and switches.
 Routers are manufactured by some popular companies like −
o Cisco

o D-Link

o HP

o 3Com

o Juniper

o Nortel

Routing Table
The functioning of a router depends largely upon the routing table
stored in it. The routing table stores the available routes for all
destinations. The router consults the routing table to determine the
optimal route through which the data packets can be sent.
A routing table typically contains the following entities −
 IP addresses and subnet mask of the nodes in the network

 IP addresses of the routers in the network

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 Interface information among the network devices and channels
Routing tables are of two types −
 Static Routing Table − Here, the routes are fed manually and are

not refreshed automatically. It is suitable for small networks

containing 2-3 routers.
 Dynamic Routing Table − Here, the router communicates with

other routers using routing protocols to determine the available

routes. It is suited for larger networks having large number of
routers.
Types of Routers

A variety of routers are available depending upon their usages. The

main types of routers are −
 Wireless Router −They provide WiFi connection WiFi devices like

laptops, smartphones etc. They can also provide standard

Ethernet routing. For indoor connections, the range is 150 feet
while its 300 feet for outdoor connections.
 Broadband Routers −They are used to connect to the Internet

through telephone and to use voice over Internet Protocol (VoIP)

technology for providing high-speed Internet access. They are
configured and provided by the Internet Service Provider (ISP).
 Core Routers −They can route data packets within a given

network, but cannot route the packets between the networks.

They helps to link all devices within a network thus forming the
backbone of network. It is used by ISP and communication
interfaces.
 Edge Routers −They are low-capacity routers placed at the

periphery of the networks. They connect the internal network to

the external networks, and are suitable for transferring data
packets across networks. They use Border Gateway Protocol
(BGP) for connectivity. There are two types of edge routers,
subscriber edge routers and label edge routers.
 Brouters − Brouters are specialised routers that can provide the

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functionalities of bridges as well. Like a bridge, brouters help to
transfer data between networks. And like a router, they route
the data within the devices of a network.

Applications of Routers:

There are various areas where a router is used:

o Routers are used to connect hardware equipment with remote
location networks like BSC, MGW, IN, SGSN, and other servers.
o It provides support for a fast rate of data transmission because it
uses high STM links for connectivity; that's why it is used in both
wired or wireless communication.
o Internet service providers widely use routers to send the data
from source to destination in the form of e-mail, a web page,
image, voice, or a video file. Furthermore, it can send data all
over the world with the help of an IP address of the destination.
o Routers offer access restrictions. It can be configured in a way
that allows for few users to access the overall data and allows
others to access the few data only, which is defined for them.
o Routers are also used by software testers for WAN
communications. For example, the software manager of an
organization is located in Agra, and its executive is located at a
different place like Pune or Bangalore. Then the router provides
the executive the method to share his software tools and other
applications with the manager with the help of routers by
connecting their PCs to the router using WAN architecture.
o In wireless networks, by configuring VPN in routers, it can be
used in the client-server model, which allows sharing the
internet, video, data, voice, and hardware resources. As shown in
the below picture:

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4. Bridge:

A bridge is a network device that connects multiple LANs (local area networks)
together to form a larger LAN. The process of aggregating networks is called
network bridging. A bridge connects the different components so that they
appear as parts of a single network. Bridges operate at the data link layer of the
OSI model and hence also referred as Layer 2 switches.
The following diagram shows a bridges connecting two LANs –

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Uses of Bridge
• Bridges connects two or more different LANs that has a similar protocol
and provides communication between the devices (nodes) in them.
• By joining multiple LANs, bridges help in multiplying the network capacity
of a single LAN.
• Since they operate at data link layer, they transmit data as data frames. On
receiving a data frame, the bridge consults a database to decide whether to
pass, transmit or discard the frame.
o If the frame has a destination MAC (media access control) address in the
same network, the bridge passes the frame to that node and then discards it.
o If the frame has a destination MAC address in a connected network, it will
forward the frame toward it.
• By deciding whether to forward or discard a frame, it prevents a single
faulty node from bringing down the entire network.
• In cases where the destination MAC address is not available, bridges can
broadcast data frames to each node. To discover new segments, they maintain
the MAC address table.
• In order to provide full functional support, bridges ideally need to be
transparent. No major hardware, software or architectural changes should be
required for their installation.
• Bridges can switch any kind of packets, be it IP packets or AppleTalk
packets, from the network layer above. This is because bridges do not examine
the payload field of the data frame that arrives, but simply looks at the MAC
address for switching.
• Bridges also connect virtual LANs (VLANs) to make a larger VLAN.

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• A wireless bridge is used to connect wireless networks or networks having
a wireless segment.
Working Principle
The working principle of a bridge is, it blocks or forwards the data depending on
the destination MAC address and this address is written into every data frame.

5 Modem:
Modem is a device that enables a computer to send or receive data
over telephone or cable lines. The data stored on the computer is
digital whereas a telephone line or cable wire can transmit only analog
data.
The main function of the modem is to convert digital signal into analog
and vice versa. Modem is a combination of two devices
− modulator and demodulator. The modulator converts digital data
into analog data when the data is being sent by the computer. The
demodulator converts analog data signals into digital data when it is
being received by the computer.

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Types of Modem

Modem can be categorized in several ways like direction in which it

can transmit data, type of connection to the transmission line,
transmission mode, etc.
Depending on direction of data transmission, modem can be of these
types −
 Simplex − A simplex modem can transfer data in only one
direction, from digital device to network (modulator) or network
to digital device (demodulator).
 Half duplex − A half-duplex modem has the capacity to transfer
data in both the directions but only one at a time.
 Full duplex − A full duplex modem can transmit data in both the
directions simultaneously.

6. Repeater:
Repeaters are network devices operating at physical layer of the OSI
model that amplify or regenerate an incoming signal before
retransmitting it. They are incorporated in networks to expand its
coverage area. They are also known as signal boosters.

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Types of Repeaters

According to the types of signals that they regenerate, repeaters can

be classified into two categories −
 Analog Repeaters −They can only amplify the analog signal.
 Digital Repeaters −They can reconstruct a distorted signal.
According to the types of networks that they connect, repeaters can
be categorized into two types –

 Wired Repeaters −They are used in wired LANs.

 Wireless Repeaters −They are used in wireless LANs and
cellular networks.
According to the domain of LANs they connect, repeaters can be
divided into two categories −
 Local Repeaters −They connect LAN segments separated by
small distance.
 Remote Repeaters −They connect LANs that are far from each
other.
Advantages of Repeaters

 Repeaters are simple to install and can easily extend the length
or the coverage area of networks.
 They are cost effective.
 Repeaters don’t require any processing overhead. The only
time they need to be investigated is in case of degradation of
performance.
 They can connect signals using different types of cables.
Disadvantages of Repeaters

 Repeaters cannot connect dissimilar networks.

 They cannot differentiate between actual signal and noise.
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 They cannot reduce network traffic or congestion.
 Most networks have limitations upon the number of repeaters
that can be deployed.
7. Cable:
To connect two or more computers or networking devices in a
network, network cables are used. There are three types of network
cables; coaxial, twisted-pair, and fiber-optic.
Coaxial cable

This cable contains a conductor, insulator, braiding, and sheath. The

sheath covers the braiding, the braiding covers the insulation, and the
insulation covers the conductor.
The following image shows these components.

Sheath

This is the outer layer of the coaxial cable. It protects the cable from
physical damage.
Braided shield

This shield protects signals from external interference and noise. This shield
is built from the same metal that is used to build the core.
Insulation
Insulation protects the core. It also keeps the core separate from the
braided shield. Since both the core and the braided shield use the
same metal, without this layer, they will touch each other and create a
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short-circuit in the wire.
Conductor

The conductor carries electromagnetic signals. Based on conductor a

coaxial cable can be categorized into two types; single-core coaxial
cable and multi-core coaxial cable.
A single-core coaxial cable uses a single central metal (usually copper)
conductor, while a multi-core coaxial cable uses multiple thin strands
of metal wires. The following image shows both types of cable.

Twisted-pair cables

The twisted-pair cable was primarily developed for computer

networks. This cable is also known as Ethernet cable. Almost all
modern LAN computer networks use this cable.

This cable consists of color-coded pairs of insulated copper wires.

Every two wires are twisted around each other to form pair. Usually,
there are four pairs. Each pair has one solid color and one stripped

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color wire. Solid colors are blue, brown, green, and orange. In stripped
color, the solid color is mixed with the white color.
Based on how pairs are stripped in the plastic sheath, there are two
types of twisted-pair cable; UTP and STP.
In the UTP (Unshielded twisted-pair) cable, all pairs are wrapped in a
single plastic sheath.
In the STP (Shielded twisted-pair) cable, each pair is wrapped with an
additional metal shield, then all pairs are wrapped in a single outer
plastic sheath.

8 Gateway:
A gateway is a network node that forms a passage between two
networks operating with different transmission protocols. The most
common type of gateways, the network gateway operates at layer
3, i.e. network layer of the OSI (open systems interconnection)
model. However, depending upon the functionality, a gateway can
operate at any of the seven layers of OSI model. It acts as the entry
– exit point for a network since all traffic that flows across the
networks should pass through the gateway. Only the internal traffic
between the nodes of a LAN does not pass through the gateway.

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Features of Gateways
 Gateway is located at the boundary of a network and manages
all data that inflows or outflows from that network.
 It forms a passage between two different networks operating
with different transmission protocols.

 A gateway operates as a protocol converter, providing

compatibility between the different protocols used in the two
different networks.
 The feature that differentiates a gateway from other network
devices is that it can operate at any layer of the OSI model.
 It also stores information about the routing paths of the
communicating networks.
 When used in enterprise scenario, a gateway node may be
supplemented as proxy server or firewall.
 A gateway is generally implemented as a node with multiple NICs
(network interface cards) connected to different networks.
However, it can also be configured using software.
 It uses packet switching technique to transmit data across the
networks.

Types of Gateways
On basis of direction of data flow, gateways are broadly divided into

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two categories –

 Unidirectional Gateways − They allow data to flow in only one

direction. Changes made in the source node are replicated in the
destination node, but not vice versa. They can be used as
archiving tools.
 Bidirectional Gateways − They allow data to flow in both
directions. They can be used as synchronization tools.

On basis of functionalities, there can be a variety of gateways, the

prominent among them are as follows −
 Network Gateway − This is the most common type of gateway

that provides as interface between two dissimilar networks

operating with different protocols. Whenever the term gateway
is mentioned without specifying the type, it indicates a network
gateway.
 Cloud Storage Gateway − It is a network node or server that

translates storage requests with different cloud storage service

API calls, such as SOAP (Simple Object Access Protocol) or REST
(Representational State Transfer).It facilitates integration of
private cloud storage into applications without necessitating
transfer of the applications into any public cloud, thus simplifying
data communication.
 Internet-To-Orbit Gateway (I2O) − It connects devices on the

Internet to satellites and spacecraft orbiting the earth. Two

prominent I2O gateways are Project HERMES and Global
Educational Network for Satellite Operations (GENSO).
 IoT Gateway − IoT gateways assimilates sensor data from IoT

(Internet of Things) devices in the field and translates between

sensor protocols before sending it to the cloud network. They
connect IoT devices, cloud network and user applications.
 VoiP Trunk Gateway − It facilitates data transmission between

plain old telephone service (POTS) devices like landline phones

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and fax machines, with VoIP (voice over Internet Protocol)
network.

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