Module 1 Introducing Computer Network
Topics
1.1 Purpose of Network
1.2 Advantages and Disadvantages of Network
1.3 Network Terminologies
1.4 Types of Network
1.5 Network Defined by Architecture
1.6 Network Topologies
1.7 Organizations Controlling Network Standards
1.8 OSI Reference Model
1.9 Introduction to TCP/IP Protocol Suite
Objectives
After Completing this lesson you will be able to:






Explain the advantages and disadvantages of network
Define network terminologies
Describe different types of network
Explain different topologies used in networking
Explain OSI reference model
Define TCP/IP protocol suite
Introduction
Communication using computer has brought revolution in the field of information technology,
particularly in the field of personal computer. Computer network allows people to access information
located in their computer from remote place. Computer networks enable sharing of resource
between systems separated from a few feet to thousands of kilometres.
A network is typically used to exchange the information and resources between the devices. The
networking process also involves designing, implementing, upgrading, managing and working with
networks and network technologies. The computers on network let the users to communicate with
each other using technologies like Internet. The main purpose of network is to share the data and
can be used to enhance the overall performance of some applications by distributing the
computation tasks to various computers on the network. Knowing how computers communicate in a
network environment is essential for being a good network professional. This module introduces
various types of networks and topologies used across the industry. It also explains various layers of
OSI networking model and TCP/IP model.
1.2 Purpose of Network
"Computer networks serve as the backbone of modern communication and collaboration.
Their primary purpose is to facilitate the seamless exchange of data and resources between
devices and systems. By enabling communication, resource sharing, and centralized
management, networks empower organizations to enhance productivity, streamline
operations, and adapt to evolving technological needs. In essence, computer networks play a
pivotal role in connecting individuals, devices, and information in today's interconnected
world."
1.2 Advantages and Disadvantages of Network
Advantages:
1. Sharing: Networks allow for the sharing of resources such as printers, files, and
internet connections among multiple devices, leading to improved efficiency and
cost savings.
2. Communication: Networks enable seamless communication through email,
instant messaging, and video conferencing, facilitating collaboration and
information exchange among users.
3. Centralized Management: Centralized management of resources, user accounts,
and security settings Resource simplifies administration and reduces overhead
costs.
4. Accessibility: Networks provide remote access to resources, allowing users to
work from anywhere with an internet connection, leading to increased flexibility
and productivity.
5. Scalability: Networks can be easily scaled up or down to accommodate changing
needs, ensuring that organizations can adapt to growth and technological
advancements.
Disadvantages:
1. Security Risks: Networks are vulnerable to security threats such as unauthorized
access, data breaches, and malware attacks, necessitating robust security
measures to mitigate risks.
2. Dependency: Organizations become dependent on network infrastructure for
their operations, making them vulnerable to disruptions caused by hardware
failures, cyberattacks, or network outages.
3. Complexity: Managing and troubleshooting network infrastructure can be
complex, requiring specialized knowledge and skills, as well as investment in
monitoring and management tools.
4. Cost: Setting up and maintaining a network can incur significant costs in terms of
hardware, software, licensing fees, and ongoing maintenance, especially for largescale deployments.
5. Performance Issues: Networks may experience performance issues such as
congestion, latency, and bandwidth limitations, impacting the speed and
reliability of data transmission.
1.3 Network Terminologies
Before we go in depth of networking concepts, it is important to be familiar with terminologies that
we use in networking.
1.3.1 Addressing
In computer networks, addressing involves assigning unique identifiers to devices or nodes
so that data can be routed to the correct destination. This can include IP addressing
(assigning IP addresses to devices in a network) or MAC addressing (assigning unique
hardware addresses to network interface controllers)
1.3.2 Acknowledgement
Acknowledgement, often abbreviated as "ACK," refers to a signal or message sent by a
receiver to indicate that it has successfully received and processed a transmitted message or
data packet. In various communication protocols and systems, acknowledgements play a
vital role in ensuring reliable data transfer.
1.3.3 Flow Control
Flow control in computer networking refers to the mechanisms used to manage the rate of
data transmission between sender and receiver to ensure that the sender does not
overwhelm the receiver with data. It is essential for maintaining optimal performance,
preventing congestion, and avoiding packet loss.
1.3.4 Segmentation
Segmentation in computer networking refers to the process of breaking down data packets
or frames into smaller units called segments for transmission across a network.
Segmentation occurs at the transport layer of the OSI (Open Systems Interconnection)
model, primarily in protocols such as TCP (Transmission Control Protocol)
1.3.5 Encryption
Encryption is the process of converting plaintext (human-readable data) into cipher text
(unreadable data) using an algorithm and a cryptographic key. It is a fundamental technique
used to secure data and communications in computer networks and information systems.
1.3.6 Compression
Compression is the process of reducing the size of data by encoding it in a more efficient
form, while still retaining the original information. Compression is widely used in computer
networks and data storage systems to reduce bandwidth usage, minimize storage space
requirements, and improve transmission speeds.
1.3.8 Media
Network media is the actual path over which an electrical signal travels as it moves from one
component to another. Examples for network media are twisted-pair cable, coaxial cable, fiber-optic
cable, and wireless.
1.3.9 Client and Server
Client and server are two parts of a software architecture model that communicate over a network or
on the same computer. A client is a computer hardware device or software that accesses a service
made available by a server. A server is a computer that provides the network resources and service to
other computers when they request it
1.3.10 Host
In computer networking, a host typically refers to any device that can send or receive data
over a network. This can include computers, servers, routers, switches, smartphones, IoT
devices, and more. Essentially, any device that is capable of communicating over a network
can be considered a host.
1.3.11 Signals
In electronics, a signal is an electric current or electromagnetic field used to convey data from one
place to another. Data is superimposed on a carrier current or wave by means of a process called
modulation. Signal modulation can be done in either of two main ways: analog and digital. In recent
years, digital modulation has been getting more common, while analog modulation methods have
been used less and less.
1.3.12 Protocols
In networking, a protocol refers to a set of rules and conventions that govern how devices
communicate and exchange data over a network. Protocols define various aspects of
network communication, including the format and structure of data packets, the procedures
for initiating and terminating connections, error handling, and more.
1 Transmission Control Protocol (TCP): Provides reliable, connection-oriented
communication between devices. TCP ensures that data is delivered in order and
without errors.
2 User Datagram Protocol (UDP): Provides connectionless, unreliable
communication between devices. UDP is often used for real-time applications
where low latency is more important than guaranteed delivery.
3 Internet Control Message Protocol (ICMP): Used for diagnostic and control
purposes in IP networks. ICMP is commonly used for tasks such as ping (testing
network connectivity) and traceroute (determining the path packets take through
a network).
4 Dynamic Host Configuration Protocol (DHCP): Allows devices to automatically
obtain IP addresses and other network configuration parameters. DHCP simplifies
network administration by dynamically assigning IP addresses as needed.
5 Domain Name System (DNS): Resolves domain names to IP addresses. DNS
translates human-readable domain names (e.g., www.example.com) into
numerical IP addresses used by networking equipment to route traffic.
6 Simple Mail Transfer Protocol (SMTP): Used for sending email messages
between servers. SMTP is a text-based protocol that defines how email messages
are formatted and transferred over the Internet.
7 File Transfer Protocol (FTP): Allows files to be transferred between a client and
a server on a network. FTP supports various operations, including uploading,
downloading, renaming, and deleting files.
1.4 Types of Network
A computer network is a group of computers linked to each other that enables the
computer to communicate with another computer and share their resources, data, and
applications.
A computer network can be categorized by their size. A computer network is mainly
of four types:
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o
LAN(Local Area Network)
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PAN(Personal Area Network)
o
MAN(Metropolitan Area Network)
o
WAN(Wide Area Network)
LAN(Local Area Network)
o
Local Area Network is a group of computers connected to each other in a small
area such as building, office.
o
LAN is used for connecting two or more personal computers through a
communication medium such as twisted pair, coaxial cable, etc.
o
It is less costly as it is built with inexpensive hardware such as hubs, network
adapters, and ethernet cables.
o
The data is transferred at an extremely faster rate in Local Area Network.
o
Local Area Network provides higher security.
PAN(Personal Area Network)
o
Personal Area Network is a network arranged within an individual person,
typically within a range of 10 meters.
o
Personal Area Network is used for connecting the computer devices of personal
use is known as Personal Area Network.
o
Thomas Zimmerman was the first research scientist to bring the idea of the
Personal Area Network.
o
Personal Area Network covers an area of 30 feet.
o
Personal computer devices that are used to develop the personal area network
are the laptop, mobile phones, media player and play stations.
There are two types of Personal Area Network:
o
Wired Personal Area Network
o
Wireless Personal Area Network
Wireless Personal Area Network: Wireless Personal Area Network is developed by
simply using wireless technologies such as WiFi, Bluetooth. It is a low range network.
Wired Personal Area Network: Wired Personal Area Network is created by using the
USB.
Examples Of Personal Area Network:
o
Body Area Network: Body Area Network is a network that moves with a
person. For example, a mobile network moves with a person. Suppose a person
establishes a network connection and then creates a connection with another
device to share the information.
o
Offline Network: An offline network can be created inside the home, so it is
also known as a home network. A home network is designed to integrate the
devices such as printers, computer, television but they are not connected to the
internet.
o
Small Home Office: It is used to connect a variety of devices to the internet
and to a corporate network using a VPN
MAN(Metropolitan Area Network)
o
A metropolitan area network is a network that covers a larger geographic area
by interconnecting a different LAN to form a larger network.
o
Government agencies use MAN to connect to the citizens and private industries.
o
In MAN, various LANs are connected to each other through a telephone
exchange line.
o
The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN,
OC-3, ADSL, etc.
o
It has a higher range than Local Area Network(LAN).
Uses Of Metropolitan Area Network:
o
MAN is used in communication between the banks in a city.
o
It can be used in an Airline Reservation.
o
It can be used in a college within a city.
o
It can also be used for communication in the military.
WAN(Wide Area Network)
o
A Wide Area Network is a network that extends over a large geographical area
such as states or countries.
o
A Wide Area Network is quite bigger network than the LAN.
o
A Wide Area Network is not limited to a single location, but it spans over a large
geographical area through a telephone line, fibre optic cable or satellite links.
o
The internet is one of the biggest WAN in the world.
o
A Wide Area Network is widely used in the field of Business, government, and
education.
Examples Of Wide Area Network:
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Mobile Broadband: A 4G network is widely used across a region or country.
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Last mile: A telecom company is used to provide the internet services to the
customers in hundreds of cities by connecting their home with fiber.
o
Private network: A bank provides a private network that connects the 44
offices. This network is made by using the telephone leased line provided by
the telecom company.
Advantages Of Wide Area Network:
Following are the advantages of the Wide Area Network:
o
Geographical area: A Wide Area Network provides a large geographical area.
Suppose if the branch of our office is in a different city then we can connect
with them through WAN. The internet provides a leased line through which we
can connect with another branch.
o
Centralized data: In case of WAN network, data is centralized. Therefore, we
do not need to buy the emails, files or back up servers.
o
Get updated files: Software companies work on the live server. Therefore, the
programmers get the updated files within seconds.
o
Exchange messages: In a WAN network, messages are transmitted fast. The
web application like Facebook, Whatsapp, Skype allows you to communicate
with friends.
o
Sharing of software and resources: In WAN network, we can share the
software and other resources like a hard drive, RAM.
o
Global business: We can do the business over the internet globally.
o
High bandwidth: If we use the leased lines for our company then this gives the
high bandwidth. The high bandwidth increases the data transfer rate which in
turn increases the productivity of our company.
Disadvantages of Wide Area Network:
The following are the disadvantages of the Wide Area Network:
o
Security issue: A WAN network has more security issues as compared to LAN
and MAN network as all the technologies are combined together that creates
the security problem.
o
Needs Firewall & antivirus software: The data is transferred on the internet
which can be changed or hacked by the hackers, so the firewall needs to be
used. Some people can inject the virus in our system so antivirus is needed to
protect from such a virus.
o
High Setup cost: An installation cost of the WAN network is high as it involves
the purchasing of routers, switches.
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Troubleshooting problems: It covers a large area so fixing the problem is
difficult.
Internetwork
o
An internetwork is defined as two or more computer network LANs or WAN or
computer network segments are connected using devices, and they are
configured
by
a
local
addressing
scheme.
This
process
is
known
as internetworking.
o
An interconnection between public, private, commercial, industrial, or
government computer networks can also be defined as internetworking.
o
An internetworking uses the internet protocol.
o
The
reference
model
used
for
internetworking
is
Open
System
Interconnection(OSI).
Types Of Internetwork:
1. Extranet: An extranet is a communication network based on the internet protocol
such as Transmission Control protocol and internet protocol. It is used for
information sharing. The access to the extranet is restricted to only those users who
have login credentials. An extranet is the lowest level of internetworking. It can be
categorized as MAN, WAN or other computer networks. An extranet cannot have a
single LAN, atleast it must have one connection to the external network.
2. Intranet: An intranet is a private network based on the internet protocol such
as Transmission Control protocol and internet protocol. An intranet belongs to an
organization which is only accessible by the organization's employee or members.
The main aim of the intranet is to share the information and resources among the
organization employees. An intranet provides the facility to work in groups and for
teleconferences.
1.5 Network Defined by Architecture
The purpose of networking is to share resources. This is accomplished by architecture of the
network operating system software. The two most common network types are peer-to-peer
and client/server.
Client-Server Network:
This model are broadly used network model. In Client-Server Network, Clients and server
are differentiated, Specific server and clients are present. In Client-Server Network,
Centralized server is used to store the data because its management is centralized. In ClientServer Network, Server respond the services which is request by Client.
Peer-to-Peer Netwo
Peer-to-Peer Network: This model does not differentiate the clients and the
servers, In this each and every node is itself client and server. In Peer-to-Peer
Network, Each and every node can do both request and respond for the services.
 Peer-to-peer networks are often created by collections of 12 or fewer
machines. All of these computers use unique security to keep their data, but
they also share data with every other node.
 In peer-to-peer networks, the nodes both consume and produce resources.
Therefore, as the number of nodes grows, so does the peer-to-peer network’s


capability for resource sharing. This is distinct from client-server networks
where an increase in nodes causes the server to become overloaded.
It is challenging to give nodes in peer-to-peer networks proper security
because they function as both clients and servers. A denial of service attack
may result from this.
The majority of contemporary operating systems, including Windows and Mac
OS, come with software to implement peer
Difference between Client-Server and Peer-to-Peer Network:
S.NO
Client-Server Network
Peer-to-Peer Network
1.
In Client-Server Network, Clients and
server are differentiated, Specific
server and clients are present.
In Peer-to-Peer Network, Clients and
server are not differentiated.
2.
Client-Server Network focuses on
information sharing.
While Peer-to-Peer Network focuses
on connectivity.
3.
In Client-Server Network,
Centralized server is used to store the
data.
While in Peer-to-Peer Network, Each
peer has its own data.
S.NO
Client-Server Network
Peer-to-Peer Network
4.
In Client-Server Network, Server
respond the services which is request
by Client.
While in Peer-to-Peer Network, Each
and every node can do both request
and respond for the services.
5.
Client-Server Network are costlier
than Peer-to-Peer Network.
While Peer-to-Peer Network are less
costlier than Client-Server Network.
6.
Client-Server Network are more
stable than Peer-to-Peer Network.
While Peer-to-Peer Network are less
stable if number of peer is increase.
7.
Client-Server Network is used for
both small and large networks.
While Peer-to-Peer Network is
generally suited for small networks
with fewer than 10 computers.
Types of Network Topology

In Computer Network ,there are various ways through which different components
are connected to one another. Network Topology is the way that defines the
structure, and how these components are connected to each other.
Types of Network Topology
The arrangement of a network that comprises nodes and connecting lines via sender
and receiver is referred to as Network Topology. The various network topologies
are:
 Point to Point Topology
 Mesh Topology
 Star Topology
 Bus Topology
 Ring Topology
 Tree Topology
 Hybrid Topology
Point to Point Topology
Point-to-Point Topology is a type of topology that works on the functionality of the
sender and receiver. It is the simplest communication between two nodes, in which
one is the sender and the other one is the receiver. Point-to-Point provides high
bandwidth.
Point to Point Topology
Mesh Topology
In a mesh topology, every device is connected to another device via a particular
channel. In Mesh Topology, the protocols used are AHCP (Ad Hoc Configuration
Protocols), DHCP (Dynamic Host Configuration Protocol), etc.
Mesh Topology
Figure 1: Every device is connected to another via dedicated channels. These
channels are known as links.
 Suppose, the N number of devices are connected with each other in a mesh
topology, the total number of ports that are required by each device is N-1. In
Figure 1, there are 5 devices connected to each other, hence the total number of
ports required by each device is 4. The total number of ports required = N * (N1).
 Suppose, N number of devices are connected with each other in a mesh topology,
then the total number of dedicated links required to connect them is NC2 i.e. N(N1)/2. In Figure 1, there are 5 devices connected to each other, hence the total
number of links required is 5*4/2 = 10.
Advantages of Mesh Topology

Communication is very fast between the nodes.
Mesh Topology is robust.
 The fault is diagnosed easily. Data is reliable because data is transferred among
the devices through dedicated channels or links.
 Provides security and privacy.
Drawbacks of Mesh Topology
 Installation and configuration are difficult.
 The cost of cables is high as bulk wiring is required, hence suitable for less
number of devices.
 The cost of maintenance is high.
A common example of mesh topology is the internet backbone, where various
internet service providers are connected to each other via dedicated channels. This
topology is also used in military communication systems and aircraft navigation
systems.

For more, refer to the Advantages and Disadvantages of Mesh Topology.
Star Topology
In Star Topology, all the devices are connected to a single hub through a cable. This
hub is the central node and all other nodes are connected to the central node. The
hub can be passive in nature i.e., not an intelligent hub such as broadcasting devices,
at the same time the hub can be intelligent known as an active hub. Active hubs have
repeaters in them. Coaxial cables or RJ-45 cables are used to connect the computers.
In Star Topology, many popular Ethernet LAN protocols are used as CD(Collision
Detection), CSMA (Carrier Sense Multiple Access), etc.
Star Topology
Figure 2: A star topology having four systems connected to a single point of
connection i.e. hub.
Advantages of Star Topology

If N devices are connected to each other in a star topology, then the number of
cables required to connect them is N. So, it is easy to set up.
 Each device requires only 1 port i.e. to connect to the hub, therefore the total
number of ports required is N.
 It is Robust. If one link fails only that link will affect and not other than that.
 Easy to fault identification and fault isolation.
 Star topology is cost-effective as it uses inexpensive coaxial cable.
Drawbacks of Star Topology
 If the concentrator (hub) on which the whole topology relies fails, the whole
system will crash down.
 The cost of installation is high.
 Performance is based on the single concentrator i.e. hub.
A common example of star topology is a local area network (LAN) in an office
where all computers are connected to a central hub. This topology is also used in
wireless networks where all devices are connected to a wireless access point.
For more, refer to the Advantages and Disadvantages of Star Topology.
Bus Topology
Bus Topology is a network type in which every computer and network device is
connected to a single cable. It is bi-directional. It is a multi-point connection and a
non-robust topology because if the backbone fails the topology crashes. In Bus
Topology, various MAC (Media Access Control) protocols are followed by LAN
ethernet connections like TDMA, Pure Aloha, CDMA, Slotted Aloha, etc.
Bus Topology
Figure 3: A bus topology with shared backbone cable. The nodes are connected to
the channel via drop lines.
Advantages of Bus Topology
 If N devices are connected to each other in a bus topology, then the number of
cables required to connect them is 1, known as backbone cable, and N drop lines
are required.
 Coaxial or twisted pair cables are mainly used in bus-based networks that support
up to 10 Mbps.

The cost of the cable is less compared to other topologies, but it is used to build
small networks.
 Bus topology is familiar technology as installation and troubleshooting
techniques are well known.
 CSMA is the most common method for this type of topology.
Drawbacks of Bus Topology
 A bus topology is quite simpler, but still, it requires a lot of cabling.
 If the common cable fails, then the whole system will crash down.
 If the network traffic is heavy, it increases collisions in the network. To avoid
this, various protocols are used in the MAC layer known as Pure Aloha, Slotted
Aloha, CSMA/CD, etc.
 Adding new devices to the network would slow down networks.
 Security is very low.
A common example of bus topology is the Ethernet LAN, where all devices are
connected to a single coaxial cable or twisted pair cable. This topology is also used
in cable television networks. For more, refer to the Advantages and Disadvantages
of Bus Topology.
Ring Topology
In a Ring Topology, it forms a ring connecting devices with exactly two neighboring
devices. A number of repeaters are used for Ring topology with a large number of
nodes, because if someone wants to send some data to the last node in the ring
topology with 100 nodes, then the data will have to pass through 99 nodes to reach
the 100th node. Hence to prevent data loss repeaters are used in the network.
The data flows in one direction, i.e. it is unidirectional, but it can be made
bidirectional by having 2 connections between each Network Node, it is called Dual
Ring Topology. In-Ring Topology, the Token Ring Passing protocol is used by the
workstations to transmit the data.
Ring Topology
Figure 4: A ring topology comprises 4 stations connected with each forming a ring.
The most common access method of ring topology is token passing.

Token passing: It is a network access method in which a token is passed from
one node to another node.
 Token: It is a frame that circulates around the network.
Operations of Ring Topology
1. One station is known as a monitor station which takes all the responsibility for
performing the operations.
2. To transmit the data, the station has to hold the token. After the transmission is
done, the token is to be released for other stations to use.
3. When no station is transmitting the data, then the token will circulate in the ring.
4. There are two types of token release techniques: Early token release releases
the token just after transmitting the data and Delayed token release releases the
token after the acknowledgment is received from the receiver.
Advantages of Ring Topology
 The data transmission is high-speed.
 The possibility of collision is minimum in this type of topology.
 Cheap to install and expand.
 It is less costly than a star topology.
Drawbacks of Ring Topology
 The failure of a single node in the network can cause the entire network to fail.
 Troubleshooting is difficult in this topology.
 The addition of stations in between or the removal of stations can disturb the
whole topology.
 Less secure.
For more, refer to the Advantages and Disadvantages of Ring Topology.
Tree Topology
This topology is the variation of the Star topology. This topology has a hierarchical
flow of data. In Tree Topology, protocols like DHCP and SAC (Standard Automatic
Configuration) are used.
Tree Topology
Figure 5: In this, the various secondary hubs are connected to the central hub which
contains the repeater. This data flow from top to bottom i.e. from the central hub to
the secondary and then to the devices or from bottom to top i.e. devices to the
secondary hub and then to the central hub. It is a multi-point connection and a nonrobust topology because if the backbone fails the topology crashes.
Advantages of Tree Topology
 It allows more devices to be attached to a single central hub thus it decreases the
distance that is traveled by the signal to come to the devices.
 It allows the network to get isolated and also prioritize from different computers.
 We can add new devices to the existing network.
 Error detection and error correction are very easy in a tree topology.
Drawbacks of Tree Topology
 If the central hub gets fails the entire system fails.
 The cost is high because of the cabling.
 If new devices are added, it becomes difficult to reconfigure.
A common example of a tree topology is the hierarchy in a large organization. At
the top of the tree is the CEO, who is connected to the different departments or
divisions (child nodes) of the company. Each department has its own hierarchy, with
managers overseeing different teams (grandchild nodes). The team members (leaf
nodes) are at the bottom of the hierarchy, connected to their respective managers and
departments.
For more, refer to the Advantages and Disadvantages of Tree Topology.
Hybrid Topology
This topological technology is the combination of all the various types of topologies
we have studied above. Hybrid Topology is used when the nodes are free to take any
form. It means these can be individuals such as Ring or Star topology or can be a
combination of various types of topologies seen above. Each individual topology
uses the protocol that has been discussed earlier.
Hybrid Topology
Figure 6: The above figure shows the structure of the Hybrid topology. As seen it
contains a combination of all different types of networks.
Advantages of Hybrid Topology
 This topology is very flexible.
 The size of the network can be easily expanded by adding new devices.
Drawbacks of Hybrid Topology
 It is challenging to design the architecture of the Hybrid Network.
 Hubs used in this topology are very expensive.
 The infrastructure cost is very high as a hybrid network requires a lot of cabling
and network devices.
A common example of a hybrid topology is a university campus network. The
network may have a backbone of a star topology, with each building connected to
the backbone through a switch or router. Within each building, there may be a bus
or ring topology connecting the different rooms and offices. The wireless access
points also create a mesh topology for wireless devices. This hybrid topology allows
for efficient communication between different buildings while providing flexibility
and redundancy within each building.