1.1 What Is a Network?

A computer network is a group of two or more devices that are connected so they can communicate and share information.

Devices on a network can include:

• Desktop computers
• Laptops
• Smartphones
• Tablets
• Servers
• Printers
• Smart TVs
• Security cameras
• Routers
• Switches
• Wireless access points
• IoT devices

Simple example

                    Internet
                       |
                     Router
                  /     |     \
              Laptop   Phone   TV
                       |
                    Printer

The laptop, phone, television, printer, and router can communicate through the network.

A network does not require the Internet

Two computers can communicate with each other locally even when there is no Internet connection.

Computer A ---- Switch ---- Computer B

Network = connected devices that can communicate and share resources.

1.2 Why Networks Are Used

Networks are used so devices and people can communicate and share resources.

File sharing

A computer can send files to another computer or access files stored on a server.

Computer A
    |
    | report.pdf
    ↓
File Server
    |
    ↓
Computer B

Printer sharing

Many users can share one network printer.

PC 1 ----\
PC 2 ----- Switch ---- Network Printer
PC 3 ----/

Internet sharing

Many devices can share one Internet connection.

             Internet
                |
              Router
          /      |      \
        PC     Phone    Tablet

Communication

Networks support:

• Email
• Instant messaging
• Video conferencing
• VoIP calls
• File transfers
• Websites
• Cloud applications

Centralized resources

Businesses can store files, applications, user accounts, and other resources centrally instead of managing everything separately on every computer.

Main purposes of networking: communication, connectivity, and resource sharing.

1.3 Clients and Servers

Two very important networking roles are the client and the server.

Client

A client requests a service or resource.

Examples include:

• A browser requesting a webpage
• An email application requesting messages
• A computer requesting a shared file
• A phone accessing cloud storage

Server

A server provides a service or resource to clients.

Examples include:

• Web server
• File server
• Email server
• DNS server
• DHCP server
• Database server

Web example

CLIENT                          SERVER

Browser ---- HTTP Request ----> Web Server

Browser <--- Webpage ----------- Web Server

File example

Employee PC ---- Request ----> File Server
Employee PC <---- File ------- File Server

Client and server describe roles. A computer can act as a client in one situation and provide a service in another.

Client = requests a service.

Server = provides a service.

1.4 Peer-to-Peer Networks

A peer-to-peer network, often called P2P, allows computers to share resources directly with each other.

Computer A ←────────→ Computer B

There does not have to be a dedicated central server.

Example

Computer A has a folder named Photos. Computer A can share that folder directly with Computer B.

Computer B
    |
    ↓
Computer A
    |
 Shared Photos

Advantages

• Simple for very small networks
• Low cost
• No dedicated server required
• Easy to create basic sharing

Disadvantages

• No centralized management
• More difficult to manage many users
• Backups may be difficult to control
• Security settings may differ on each computer
• Does not scale well to large organizations

Peer-to-peer = computers can share resources directly with each other.

1.5 LAN

LAN means Local Area Network.

A LAN normally covers a relatively small geographic area.

Examples include:

• A home
• An office
• A school classroom
• A computer laboratory
• A retail store
• One building

Office example

PC 1 ----\
PC 2 ----- Switch ---- Router ---- Internet
PC 3 ----/
Printer --/

The computers, printer, switch, and router inside the office can form a LAN.

LANs commonly use Ethernet and Wi-Fi.

LAN = Local Area Network = network covering a small local area.

1.6 WAN

WAN means Wide Area Network.

A WAN connects networks over larger geographic distances.

It may connect offices located in different cities, provinces, countries, or continents.

Example

Toronto Office LAN
        |
        |
       WAN
        |
        |
Vancouver Office LAN

Each office can have its own LAN, while a WAN connects the two LANs.

WAN services are often provided through telecommunications companies or Internet service providers.

The Internet is the largest well-known example of interconnected wide-area networking.

LAN = local area. WAN = large geographic area.

1.7 MAN

MAN means Metropolitan Area Network.

A MAN generally covers an area larger than a LAN but smaller than a large WAN.

It commonly connects networks across a city or metropolitan region.

Example

Building A LAN
      |
      |
 Metropolitan Network
      |
   +--+--+
   |     |
Building B LAN
Building C LAN

A university, government organization, or large company could use a metropolitan network to connect buildings located across the same city.

MAN = network covering a metropolitan or city-sized area.

1.8 PAN

PAN means Personal Area Network.

A PAN is a very small network built around one person's devices.

Examples

• Phone connected to Bluetooth earbuds
• Smartwatch connected to a smartphone
• Wireless keyboard connected to a computer
• Wireless mouse connected to a laptop
• Phone connected to another personal device

        Smartwatch
            |
            |
Earbuds -- Phone -- Laptop

PAN connections normally operate over short distances.

Bluetooth is one technology commonly used for personal area networking.

PAN = Personal Area Network = very short-range personal networking.

1.9 WLAN

WLAN means Wireless Local Area Network.

A WLAN is a local network that uses wireless communication.

Wi-Fi is the most common example.

Example

Laptop   )))
Phone    ))) ---- Wireless Access Point ---- Network
Tablet   )))

A wireless access point allows devices to connect to the LAN without using an Ethernet cable for each device.

Benefits

• Mobility
• Fewer cables
• Easy connection for phones and tablets
• Flexible device placement

Things administrators must consider

• Signal strength
• Coverage
• Interference
• Security
• Capacity
• Wireless congestion

WLAN = Wireless Local Area Network.

1.10 Internet

The Internet is a worldwide collection of interconnected networks.

It allows computers, phones, servers, and other devices around the world to communicate.

Simple connection path

Your Laptop
    |
Home Router
    |
Internet Service Provider
    |
Internet
    |
Web Server

Services using the Internet include:

• Websites
• Email
• Cloud storage
• Online games
• Video streaming
• Video conferencing
• File transfers
• Remote access

Internet versus Web

The Internet is the global network infrastructure.

The World Wide Web is one service that operates over the Internet.

Internet = worldwide system of interconnected networks.

1.11 Intranet

An intranet is a private network or private internal service used by an organization.

It may use technologies similar to the Internet, but access is restricted to authorized users.

Company example

A company may have an internal employee website containing:

• Company policies
• Training documents
• Employee schedules
• Internal forms
• Announcements
• Internal applications

Employee
   |
Login
   |
Company Intranet
   |
Internal Resources

The public normally cannot access these internal resources.

Intranet = private internal organizational network or service.

1.12 Extranet

An extranet gives selected authorized users outside an organization access to certain private resources.

External users might include:

• Suppliers
• Customers
• Business partners
• Contractors
• Vendors

Example

A supplier may log in to a secure company portal to check inventory requirements.

Supplier
   |
Secure Login
   |
Extranet Portal
   |
Selected Company Resources

The supplier does not receive access to the entire internal network. Only approved resources are made available.

Remember the difference

Internet
Public/global

Intranet
Private/internal

Extranet
Controlled access for authorized outsiders

1.13 Network Resources

A network resource is something that users or devices can access through a network.

Common resources

• Shared files
• Folders
• Printers
• Storage systems
• Databases
• Applications
• Internet connections
• Servers
• Websites
• Cloud services

Shared file example

PC 1 ----\
PC 2 ----- Switch ---- File Server
PC 3 ----/

All authorized computers can access files stored on the server.

Shared printer example

Laptop ----\
Desktop ---- Switch ---- Network Printer
Server ----/

Permissions can control which users are allowed to access particular resources.

Network resource = something made available through a network.

1.14 Network Devices Overview

Networks use specialized devices to connect systems and move, control, or protect network traffic.

Switch

A switch connects devices within a local network.

PC ----\
PC ----- Switch ---- Server
Printer/

Router

A router connects different networks.

Home LAN ---- Router ---- Internet

Wireless Access Point

An access point allows wireless devices to connect to a network.

Phone   )))
Laptop  ))) ---- Access Point ---- Switch
Tablet  )))

Firewall

A firewall examines network traffic and applies security rules.

Internet ---- Firewall ---- Internal Network

Modem or provider equipment

Provider equipment can connect a customer's network to the service provider.

Beginner memory

Switch
Connects local devices

Router
Connects networks

Access Point
Provides wireless access

Firewall
Controls traffic using security rules

1.15 Network Services Overview

A network service is a function made available to devices or users through a network.

DNS

DNS translates names into IP addresses.

easytutorguide.com
        |
       DNS
        |
   IP Address

DHCP

DHCP automatically gives devices network configuration information.

This can include:

• IP address
• Subnet mask
• Default gateway
• DNS server information

File services

File servers store and share files.

Web services

Web servers provide webpages and web applications.

Email services

Mail servers help send, receive, and store email.

Authentication services

Authentication services can verify user identities before allowing access to resources.

Networks provide both physical connectivity and logical services.

1.16 Network Performance Basics

Network performance describes how well the network moves information and responds to users.

Bandwidth

Bandwidth represents the capacity of a network connection.

100 Mbps
1 Gbps
10 Gbps

Throughput

Throughput is the amount of data actually transferred.

Bandwidth  = 1 Gbps
Throughput = 750 Mbps

Latency

Latency means delay.

5 ms   = low delay
200 ms = higher delay

Jitter

Jitter means variation in delay.

Packet 1 = 20 ms
Packet 2 = 95 ms
Packet 3 = 30 ms
Packet 4 = 140 ms

Packet loss

Packet loss occurs when packets fail to reach their destination.

Packet 1 → ✓
Packet 2 → ✓
Packet 3 → X
Packet 4 → ✓

Good network performance

A well-performing network generally tries to provide:

• High useful throughput
• Low latency
• Low jitter
• Low packet loss
• Reliable connectivity

Bandwidth = capacity. Throughput = actual transfer. Latency = delay. Jitter = variation in delay.

1.17 Network Security Basics

Network security protects devices, users, services, and information from unauthorized access, attacks, damage, and misuse.

Authentication

Authentication verifies who a user is.

User
 |
Username + Password
 |
Authentication
 |
Access

Authorization

Authorization determines what an authenticated user is allowed to do.

Firewall

A firewall can allow or block traffic according to security rules.

Encryption

Encryption helps protect information from being read by unauthorized people.

Updates and patches

Security updates help correct known vulnerabilities in software and network devices.

Least privilege

Users should receive only the access required to perform their jobs.

Other security practices

• Strong passwords
• Multi-factor authentication
• Network monitoring
• Backups
• Device updates
• Secure Wi-Fi
• Access controls
• Network segmentation

Network security uses people, policies, configuration, monitoring, and technology together.

1.18 Network Documentation Basics

Network documentation records important information about how a network is designed, configured, connected, and maintained.

Network diagrams

A network diagram shows devices and their connections.

Internet
   |
Firewall
   |
Router
   |
Switch
 / | \
PC AP Server

IP address documentation

Administrators may record network addresses and the devices using them.

Device documentation

Documentation may include:

• Device names
• Device models
• Serial numbers
• Physical locations
• Management addresses
• Configuration information

Cabling documentation

Administrators may document which wall jack connects to which patch panel and switch port.

Change documentation

When an administrator changes an important network configuration, the change should be recorded.

Why documentation matters

Good documentation makes troubleshooting, maintenance, upgrades, and disaster recovery easier.

Good documentation should be accurate, organized, and kept up to date.

1.19 Network Administrator Roles

A network administrator helps install, configure, maintain, monitor, secure, and troubleshoot computer networks.

Common responsibilities

• Configuring switches
• Configuring routers
• Managing wireless networks
• Managing IP addressing
• Monitoring network performance
• Troubleshooting connectivity
• Maintaining documentation
• Applying security settings
• Installing updates
• Managing network access
• Maintaining backups
• Working with Internet providers

Troubleshooting example

A user reports:

“My computer cannot access the Internet.”

The administrator might investigate:

Computer
   ↓
Network Interface
   ↓
Cable or Wi-Fi
   ↓
Switch / Access Point
   ↓
Router
   ↓
DNS / DHCP
   ↓
Internet Provider

The administrator must determine where the failure is occurring.

Technical and communication skills

Network administrators need technical knowledge, but they also need good communication, organization, documentation, and troubleshooting skills.

Network administrator = keeps the network available, secure, organized, and working correctly.

1.20 Networking Exam Overview

Networking exams often test whether you can understand a situation and choose the correct networking concept.

Do not only memorize definitions. Learn how to recognize clues inside a question.

LAN example

A company has computers connected inside one office building. What type of network is this?

Answer: LAN

The important clue is that the network covers a small local area.

WAN example

A company connects its Toronto office to its Vancouver office. Which type of network is most appropriate?

Answer: WAN

WLAN example

Employees connect laptops to the local network through Wi-Fi. What type of local network is being used?

Answer: WLAN

Client and server example

A laptop requests a webpage from another system. What role is the laptop performing?

Answer: Client

Performance example

A user experiences noticeable delay during a video call. Which performance measurement should be investigated?

Answer: Latency

Security example

A network device allows or blocks traffic according to security rules. Which device is being described?

Answer: Firewall

Chapter 1 memory table

Final Chapter 1 review

1.1  What Is a Network?
1.2  Why Networks Are Used
1.3  Clients and Servers
1.4  Peer-to-Peer Networks
1.5  LAN
1.6  WAN
1.7  MAN
1.8  PAN
1.9  WLAN
1.10 Internet
1.11 Intranet
1.12 Extranet
1.13 Network Resources
1.14 Network Devices Overview
1.15 Network Services Overview
1.16 Network Performance Basics
1.17 Network Security Basics
1.18 Network Documentation Basics
1.19 Network Administrator Roles
1.20 Networking Exam Overview

These 20 right-side sections now match the 20 Chapter 1 sidebar links exactly.