Module 1

Introduction to Computer Networks and Networking Concepts

Introduction

Networks are vital to the business of computers, especially for the applications and data that networks
can deliver. If a single computer with standard desktop software can make anyone more productive, then
interconnecting computers on a network and bringing people and data together improves communication, fosters
productivity and creates opportunities for collaborating and exchanging information quickly and easily.
As a future computer engineer, in the field of network administration, you must understand the
fundamental concepts in creating a network and making any network perform correctly. It’s also important to
understand what’s involved in networked communications and which network models are best in different
situations. This knowledge gives you a solid foundation for network design, implementation, and troubleshooting.

Learning Objectives

At the end of this module, you will be able to:

1. Describe the fundamental reasons for networking
2. Identify essential network components
3. Identify and evaluate network criteria
4. Compare different types of networks
5. Apply your knowledge when selecting a network type

Key Concepts

Networking is the concept of sharing resources and services. A network of computers is a group of
interconnected systems sharing resources and interacting using a shared communications link. A network,
therefore, is a set of interconnected systems with something to share. The shared resource can be data, a
printer, a fax modem, or a service such as a database or an email system. The individual systems must be
connected through a pathway (called the transmission medium) that is used to transmit the resource or service
between the computers. All systems on the pathway must follow a set of common communication rules for data
to arrive at its intended destination and for the sending and receiving systems to understand each other. The
rules governing computer communication are called protocols.

In summary, all networks must have the following:

• At least two computers to connect (Clients, Servers, Peers)

• A resource to share (resource or information sharing)
• A pathway to transfer data (transmission medium and connectivity devices)
• A set of rules governing how to communicate (protocols)

A more detailed discussion on the different network components in the following modules.
NOTE
 Having a transmission pathway does not always guarantee communication. When two entities communicate,
they do not merely exchange information; rather, they must understand the information they receive from each
other. The goal of computer networking, therefore, is not simply to exchange data but to understand and use
data received from other entities on the network. An analogy is people speaking. Just because two people can
speak, it does not mean they automatically can understand each other. These two people might speak different
languages or interpret words differently. One person might use sign language, while the other uses spoken
language. As in human communication, even though you have two entities who “speak,” there is no guarantee
they will be able to understand each other. Just because two computers are sharing resources, it does not
necessarily mean they can communicate.

Because computers can be used in different ways and can be located at different distances from each other,
enabling computers to communicate often can be an overwhelming task that draws on a wide variety of
technologies. The two main reasons for using computer networking are to provide services and to reduce
equipment costs. Networks enable computers to share their resources by offering services to other computers
and users on a network. The following are some specific reasons for networking PCs:
• Resource Sharing
• Reduced Cost Easier Installation of Software
• Improved Security
• Improved Communications
• More Workplace Flexibility
• Reduced cost of Hardware Peripherals
• Centralized Administration

NETWORK CRITERIA

1. Performance – can be measured in many ways including transit and response time. Transit time is the
amount of time required for a message to travel from one device to another. Response time is the elapsed
time between an inquiry and a response. The performance of the network depends on many factors
including the number of users, type of transmission medium, the capabilities of the connected hardware,
and the efficiency of the software. Performance is often evaluated by two networking metrics: throughput
and delay. Users often need more throughputs and less delay.
2. Reliability – In addition to accuracy of delivery, network reliability is measured by the frequency of failure,
the time it takes a link to recover from a failure, and the network’s robustness in a catastrophe.
3. Security – includes protecting data from unauthorized access, protecting data from damage and
development, and implementing policies and procedures for recovery from breaches and data losses.

NETWORK CLASSIFICATION

A. Distance Factor

Networks come in all shapes and sizes. Network administrators often classify networks according to
geographical size. Networks of similar size have many similar characteristics.

1. Personal Area Network - A Personal Area Network or PAN has been around for quite sometime and this
type of network focuses on a person’s workspace. A Personal Area Network handles data transmission
within devices such as tablets, personal digital assistants, smartphones, and computers. Note that single
users in most cases basically use this type of network. People make use of these types of networks
commonly in situations where they need to connect wearable or mobile devices.
2. Local Area Networks (LANs) - A Local Area Network or LAN as it’s commonly known is a network that
connects devices usually in the same building or local area. This could be computers or other devices
that are within an office building, which are connected together to share resources. Most people make
use of this network type to share files and other business-related documents in an organization. A
router is often used when multiple Local Area Networks need to be connected to each other. A LAN is
probably the most commonly used computer network nowadays. A major component of a LAN
network is a Layer2 Ethernet Switch which provides the actual communication between devices.

LANs are characterized by the following:

• They transfer data at high speeds (higher bandwidth).

• They exist/operate within a limited geographical area.
• Connectivity and resources, especially the transmission media,
usually are managed by the company running the LAN.
• Connect physically adjacent devices
• Some LAN technologies:
- Ethernet and Token ring

3. Metropolitan Area Network (MAN) - When it comes to the MAN network type, know that it is usually a
large computer network on a large geographical area that includes several buildings and LANs, or even
the entire city or metropolitan area. The geographical area of the MAN is larger than LAN, but smaller
than WAN, which makes it fall in between a Local Area Network and a Wide Area Network.

A MAN is a network that spans a metropolitan are,

such as city or a suburban area. The following features
differentiate a MAN from LANs and WANs:
• MAN interconnect users in a geographic area or
region larger than that covered by a LAN but smaller than
the area covered by WAN
• MANs also are used to interconnect several LANs by
bridging them with backbone lines.
4. Wide Area Networks (WANs) - Unlike Local Area Networks and Metropolitan Area Networks, Wide Area
Networks or WAN are networks that span over wide geographical locations, which could be multiple
buildings or even multiple cities or countries. This kind of network is suitable for providing Internet access
to Local Area Networks or some other kinds of networks. Wide area network communications often
require networking devices such as routers and modems for effective data communication. Moreover,
WANs are usually provided by ISPs which are interconnected to offer communication to wider areas. A
WAN link is usually referring to a network interface that provides connection of the smaller network
towards the bigger WAN network. A WAN link can be fiber optic, Ethernet Layer2 VPN, etc.

A wide area network (WAN) interconnects LANs. WANs provide LANs access to computer or file
servers in other (distant) locations. A WAN can be located entirely within a state or a country, or it can
be interconnected around the world. Collaboration software provides access to real time information and
resource that allow meeting to be held remotely instead of in person (telecommuting). WANs are
characterized by the following:

• They operate over very large, geographically separated areas;

• They usually interconnect multiple LANs.
• They often transfer data at lower speeds (lower bandwidth).
• Connectivity and resources, especially the transmission media, usually are managed by a third-
party carrier such as a telephone or cable company.
• Some WAN technologies:
Modems (asynchronous dial-up), ISDN, DSL, Frame Relay, SONET, T-leased lines

WANs can be further classified into two categories: enterprise WANs and global WANs. An enterprise
WAN connects the widely separated computer resources of a single organization. An organization with
computer operations at several distant sites can employ an enterprise WAN to interconnect the sites. An
enterprise WAN can combine private and commercial network services, but it is dedicated to the needs
of a particular organization. A global WAN interconnects networks of several corporations or
organizations.

5. Wireless LAN - Unlike Local Area Network, a Wireless LAN network

doesn’t make use of a cable for end-to-end connectivity. A WLAN
makes use of a Wireless Access Point (WAP) device, which serves as
the point of connectivity for wireless clients on the network.
6. Virtual Private Network (VPN) - A Virtual Private Network is a type of network that makes use of existing
private or public network infrastructure (e.g the Internet) to provide a secured network connection. This
is often achieved by creating an encrypted tunnel for secured end-to-end connectivity. A Virtual Private
Network uses data encryption techniques to provide security for files that are sent or received over the
network. This is often used by organizations that have highly sensitive data to transfer.

For example, using VPN, a telecommuter can access the company’s headquarters’ network through the
internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the
headquarters.

Benefits of VPN:
• Access VPNs provide remote access for a mobile worker and small office/home office to the headquarters
intranet over a shared infrastructure
• Intranet VPNs link regional or remote offices to headquarters’ internal network over a shared
infrastructure. (it allows access only to the enterprise customer employees)
• Extranet VPNs link business partners to he headquarters’ network over a shared infrastructure using
dedicated connections. (it allows access to users outside the enterprise)

7. Storage Area Network (SAN) - A Storage Area Network or SAN is a network that has been designed for
storing and transferring files. This network setup is often made up of servers with large storage
capacity and special switches and interface cards. There are many reasons why any organization would
make use of a Storage Area Network, and one of them is to provide a safe place for storing important
files and for providing a fast network for backing up files. Storage Area Networks are often designed to
have high availability, because files must be accessible at any given time. Also, a SAN might not use
the classical TCP/IP used in other computer networks but some special protocols such as Fiber Channel
Protocol, SCSI over FCP etc.
8. Enterprise Internal Private Network - An
Enterprise Internal Private Network is a type of
network that is designed for private
communication within an organization. This type
of network is only accessible from within the
enterprise since its major goal is to provide
security for users within the organization. A
firewall is often used when users need to access
information on the Internet. Although it’s a
private network, it does not mean that its only
available within a building. It can span several buildings using private communication lines.

9. Campus Area Network - Campus Area Networks are basically made up of several Local Area Networks,
which are often within a campus area. Campus Area Networks are used in places such as hospitals,
schools, universities or any organization that has multiple LANs and buildings that need to connect to
each other to share resources.

10. System Area Network - A System Area Network is a

network that is designed to work in parallel computing
environments; it connects computers that are in a High
Performance Computing setting. These are often used
where high processing is needed. Computer clusters
make use of System Area Networks to achieve
connectivity. The major difference here is the distance
in between the computers on the network, which is
often a short distance.
B. Architecture (based on security, protocol and processes used)

Networks generally fall into one of two broad network categories in terms of its architecture:

• Client/server networks
• Peer-to-peer networks

It is important to remember that one type of networking configuration is not necessarily better than
another. Each type of networking model has its own strengths and weaknesses.

1. Client/Server-Based Networking

A client/server network consists of a group of

user-oriented PCs (called clients) that issue requests to a
server. The client PC is responsible for issuing requests
for services to be rendered. The server’s function on the
network is to service these requests. Servers generally
are higher-performance systems that are optimized to
provide network services to other PCs. The server
machine often has a faster CPU, more memory, and more
disk space than a typical client machine.

Some common server types include file servers,

mail servers, print servers, fax servers, and application
servers. In a client/server network, the server machines often are not even set up to do the tasks that a
client machine can do. Although this discussion should have made it clear how they differ, people often
confuse mainframe computing with a client/server-based network. The two approaches to computing are
not the same, however. In mainframe computing, the dumb terminal does not process any requests. It
simply acts as an interface to receive input and to display output. Only the mainframe computer can process
information. In a client/server model, the client PC can process information, but certain services are offloaded
to the server machine. The server machine’s role is simply to process the requests made for these services
by the client. In short, a client/server-based network is one in which certain tasks run on and utilize the
resources of one machine while others utilize another machine, each according to its functional role. In
summary, the client/server model is a network in which the role of the client is to issue requests and the
role of the server is to service requests.

Advantages:
✓Centralized user accounts, security, backups and access controls simplify network administration
✓More powerful equipment means a more efficient access to network resources
✓A single password for network logon delivers access to all networks.
✓A server-based networking makes the most sense for networks with 10 or more users or any networks
where resources are used heavily. Highly expandable
Disadvantages:
✓ At worst, server failure renders a network unusable; It results in loss of network resources.
✓ It requires expert staff, which increases expenses
✓ Dedicated hardware and specialized software (networking operating system) add to cost.

2. Peer-to-Peer Networking

A peer-to-peer network consists of a group of PCs that operate as equals. Each PC is called a peer.
The peers share resources (such as files and printers) just like in a server-based network, although no
specialized or dedicated server machines exist. In short, each PC can act as a client or a server. No one
machine is set up with a high-powered set of devices, nor is any one PC set up simply to provide one service
(such as storing files). Small networks—usually with fewer than 10 machines—can work well in this
configuration. In larger networks, companies usually move to a server-based network because many clients
requesting to use a shared resource can put too much strain on one client’s PC.

Examples of peer-to-peer networks include Windows for Workgroups, Windows 95, and Windows NT
Workstation. Many actual network environments consist of a combination of server-based and peer-to-peer
networking models. In the real world, companies often grow from a peer-to-peer network into a client/server-
based network. The following analogy might help you better understand the use of each type of network. A
small company of 10 employees might choose to implement a carpool strategy. Let’s say four employees get
together, and each takes a turn driving the other three employees to work. This is analogous to a peer-to-
peer network. Just like a peer-to-peer network, in which no one PC is responsible for dedicating itself to
providing a service, no one car is dedicated to providing transportation. As the company grows to 400
employees, it might be decided that the number of employees justifies the purchase of a dedicated ridepool
van with a dedicated driver. This is analogous to a client/server network, in which a dedicated machine is
used to provide a service. In this example, the company has dedicated a van to providing a ride-share
service.

As you can see in this analogy, no single network model fits all situations. A car pool in a small
company is an efficient and cost-effective way to get
people to work. A bus probably is not economically
feasible for a small company. In a big company,
however, the use of a bus becomes feasible. Peer-to-
peer networks can work well for small workgroups.
Client/server networks provide the necessary resources
for larger groups of users.

Advantages:
✓ Easy to install and configure
✓ Individual machines do not depend on the presence
of a dedicated server.
✓ Individual users control their own shared resources
✓ Inexpensive to purchase and operate
✓ Needs no additional hardware or software beyond a
suitable operating system
✓ No dedicated administrator needed
✓ Works best for networks with 10 or fewer users.

Disadvantages:
✓ Network security applies only to a single resource at a time
✓ Users may be forced to use many passwords as there are shared resources
✓ Each machine must be backed up individually to protect all shared data
✓ Reduced performance
✓ No centralized organizational scheme to locate or control access to data
✓ Does not usually work well with more than 10 users.

Summary
1. The basic elements of all networks include a network medium and an interface to that medium, a
common protocol to communicate and network software.
2. Networks deliver services such as file and resource sharing, email and messaging services, and more.
3. A network can be evaluated in terms of its performance, reliability and security.
4. Computer network types can be grouped by distance and architecture. In terms of distance, a
network can be PAN, LAN, WAN, MAN, WLAN and others. Peer-to-peer networks and server-based
networks are the two types if described in terms of its architecture.
Learning Resources/References

1. https://www.networkstraining.com/different-types-of-networks/
2. Tomsho, et.al: Guide to Networking Essentials 5th Edition
3. Dye, et.al: Network Fundamentals CCNA Exploration Companion Guide

Study Questions
1. In addition to data networks, what other breakthroughs in communication media have extended the
reach of human interactions?
2. How has data networking changed your community (your family, school, city, or country?)
3. Early data networks carried character-based messages between computer systems. What types of
network traffic do modern networks carry, and how has this changed human interactions?

Learning Activities

Case Study

XYZ corporation currently employs eight people but plans to hire more in the next five months. Users
will work on multiple projects, and only those assigned to a project should have access to the project
files. You’re instructed to set up a network to make it easy to manage and backup. Would you choose a
peer-to-peer network, a server-based network or a combination of both? Why?