Networking II: SSS 3 Lesson Note

NETWORKING II: IP ADDRESSING, IPV4, SUBNETTING AND NETWORK PROTOCOLS

Subject: Digital Technologies

Class: SSS 3

Term: First Term

Week: 6

Topic: Networking II

Duration: 80 Minutes (Double Period)

1. Introduction

Computer networking allows computers and other digital devices to communicate and share information. For devices to exchange data successfully, they need ways to identify one another and rules that govern how information is transmitted. In a computer network, an IP address helps identify a device or network interface for communication using the Internet Protocol. Network protocols define how devices exchange information, while subnetting allows a larger IP network to be divided into smaller networks. This lesson examines IP addressing, IPv4, subnetting and common network protocols.

Definition: IP addressing is the system of assigning Internet Protocol addresses to network interfaces so that devices can be identified and communicate across IP networks.

2. Meaning of an IP Address

An IP address is a numerical address assigned to a network interface. It helps network devices identify the source and destination of data packets. For example, a computer connected to a school network may have an IPv4 address such as 192.168.1.10. When the computer communicates with another device, IP addressing helps the network deliver packets towards the intended destination.

Functions of an IP Address

1. Identification: It identifies a network interface within the relevant addressing system.
2. Routing: It helps routers determine where IP packets should be forwarded.
3. Communication: It enables devices to send and receive IP packets across networks.
4. Network organisation: IP addresses and subnet masks help distinguish network portions from host portions of an address.

Important: An IP address does not necessarily identify a person or a physical computer permanently. Addresses may change, and one device can have multiple network interfaces or addresses.

3. Types of IP Addresses

The two major versions of Internet Protocol addressing are IPv4 and IPv6.

3.1 Internet Protocol Version 4 (IPv4)

IPv4 is the fourth version of the Internet Protocol. It uses a 32-bit address, commonly written as four decimal numbers separated by dots. Each decimal number is called an octet because it represents eight bits. Each octet ranges from 0 to 255. Example:

192.168.1.10

The four octets can be represented in binary as follows:

Decimal:  192       168       1         10
Binary:   11000000  10101000  00000001  00001010

An IPv4 address contains 32 bits in total. The total number of possible IPv4 address patterns is:

2^32 = 4,294,967,296

Some addresses and address ranges are reserved for special purposes, so this total is not the number of ordinary public addresses available for general assignment.

3.2 Internet Protocol Version 6 (IPv6)

IPv6 was developed partly to address the limitations of IPv4 address availability. It uses 128-bit addresses written in hexadecimal groups separated by colons. Example:

2001:db8::1

IPv6 provides a vastly larger address space than IPv4 and includes other improvements to IP addressing and network operation.

Differences Between IPv4 and IPv6

Feature	IPv4	IPv6
Address length	32 bits	128 bits
Notation	Decimal numbers separated by dots	Hexadecimal groups separated by colons
Example	192.168.1.10	2001:db8::1
Address space	Approximately 4.3 billion possible patterns	Approximately 3.4 × 1038 possible patterns
Broadcasting	Supports broadcast addressing	Does not use broadcast; it supports multicast and anycast instead

4. Public and Private IPv4 Addresses

IPv4 addresses can be classified according to how they are used.

4.1 Public IP Addresses

A public IP address is globally unique within the public addressing system and is used for communication across the internet. Public addresses are allocated through internet address registries and service providers. Example: A public-facing web server may have a public IP address that internet users can reach.

4.2 Private IP Addresses

Private IPv4 addresses are reserved for use within private networks, such as homes, schools and offices. They are not routed directly across the public internet. The three private IPv4 ranges are:

Private Range	Subnet Mask at the Range Boundary	Common Use
10.0.0.0 – 10.255.255.255	255.0.0.0 (/8)	Large private networks
172.16.0.0 – 172.31.255.255	255.240.0.0 (/12)	Medium or large private networks
192.168.0.0 – 192.168.255.255	255.255.0.0 (/16)	Home, school and small office networks

Note: The subnet masks shown above describe the boundaries of the reserved private ranges. A network administrator may divide these ranges into smaller subnets with different subnet masks.

A router commonly allows devices using private addresses to access the internet through Network Address Translation (NAT), often using a public address.

4.3 Static and Dynamic IP Addresses

Static IP address: An address configured to remain fixed unless an administrator or network configuration changes it. Dynamic IP address: An address assigned automatically, commonly through the Dynamic Host Configuration Protocol (DHCP). It may change when the lease is renewed or the device reconnects.

5. Subnet Masks and CIDR Notation

A subnet mask helps determine which bits of an IPv4 address represent the network portion and which bits represent the host portion. For example:

IP address:  192.168.1.10
Subnet mask: 255.255.255.0
CIDR:        /24

The subnet mask 255.255.255.0 corresponds to /24 because the first 24 bits are network bits. The remaining 8 bits are available for host addressing within that subnet.

Understanding CIDR Notation

CIDR stands for Classless Inter-Domain Routing. It expresses the length of the network prefix using a slash followed by a number. Examples:

• /8 means the first 8 bits form the network prefix.
• /16 means the first 16 bits form the network prefix.
• /24 means the first 24 bits form the network prefix.
• /26 means the first 26 bits form the network prefix.

The larger the prefix length, the more bits are used for the network prefix and the fewer bits remain for host addresses within that subnet.

Common IPv4 Subnet Masks

CIDR Prefix	Subnet Mask	Total Addresses	Usable Host Addresses in a Typical Subnet
/24	255.255.255.0	256	254
/25	255.255.255.128	128	126
/26	255.255.255.192	64	62
/27	255.255.255.224	32	30
/28	255.255.255.240	16	14

The usable-host counts above assume an ordinary IPv4 subnet in which the network address and broadcast address are not assigned to hosts. Special cases, such as certain point-to-point links, may use different rules.

6. Meaning and Importance of Subnetting

Definition: Subnetting is the process of dividing a larger IP network into smaller logical networks called subnets.

Subnetting allows an organisation to organise its devices into separate networks instead of placing every device on one large network.

Importance of Subnetting

1. Better organisation: Devices can be grouped by department, classroom, office or function.
2. Efficient address allocation: IP addresses can be assigned according to the number of devices required in each subnet.
3. Reduced broadcast domains: Routers separate broadcast domains, helping limit broadcast traffic within each subnet.
4. Improved security management: Different subnets can be controlled through routing rules and access-control policies.
5. Easier troubleshooting: Network administrators can isolate and diagnose problems within smaller network segments.
6. Improved network management: Separating departments or services makes network administration more organised.

7. Basic Subnetting Calculation

Consider the network:

192.168.1.0/24

A /24 network contains 32 − 24 = 8 host bits. The total number of addresses is:

2^8 = 256 addresses

In a typical IPv4 subnet, two addresses are reserved: one for the network address and one for the broadcast address. Therefore:

Usable host addresses = 256 − 2
                      = 254

Example: Dividing a /24 Network into Two /25 Subnets

Suppose a school has the network 192.168.1.0/24 and wants to divide it into two equal subnets. Moving from /24 to /25 uses one additional bit for the network prefix. The network is divided into two equal groups, each containing 128 addresses.

Feature	Subnet 1	Subnet 2
Network address	192.168.1.0/25	192.168.1.128/25
First usable address	192.168.1.1	192.168.1.129
Last usable address	192.168.1.126	192.168.1.254
Broadcast address	192.168.1.127	192.168.1.255
Total addresses	128	128
Usable host addresses	126	126

The first subnet can serve one computer laboratory, while the second can serve another laboratory or office, provided the network is configured accordingly.

Key formula:
Total addresses in a conventional IPv4 subnet = 2^{host bits}.
Usable host addresses are generally total addresses minus 2.

Another Example: A /26 Subnet

A /26 prefix leaves 32 − 26 = 6 host bits.

Total addresses = 2^6 = 64
Usable hosts    = 64 − 2 = 62

For the subnet 192.168.1.0/26:

• Network address: 192.168.1.0
• First usable address: 192.168.1.1
• Last usable address: 192.168.1.62
• Broadcast address: 192.168.1.63
• Subnet mask: 255.255.255.192

The next /26 subnet begins at 192.168.1.64.

8. Meaning of Network Protocols

Definition: A network protocol is a set of rules that governs how devices communicate and exchange data over a network.

Protocols help devices understand how data should be formatted, addressed, transmitted, received and interpreted. Different protocols perform different tasks. Some support reliable data delivery, others translate domain names into IP addresses, and others support web browsing, email or automatic network configuration.

9. Common Network Protocols and Their Functions

Protocol	Full Meaning	Function
IP	Internet Protocol	Addresses and routes packets between networks.
TCP	Transmission Control Protocol	Provides reliable, ordered delivery of data between applications.
UDP	User Datagram Protocol	Provides a lightweight, connectionless method of sending datagrams without TCP's delivery guarantees.
HTTP	Hypertext Transfer Protocol	Transfers web resources between clients and servers.
HTTPS	Hypertext Transfer Protocol Secure	Protects HTTP communication using TLS encryption and authentication.
FTP	File Transfer Protocol	Supports file transfers between computers. Traditional FTP does not encrypt traffic.
SMTP	Simple Mail Transfer Protocol	Used to send email and relay messages between mail servers.
POP3	Post Office Protocol Version 3	Allows an email client to retrieve messages from a mail server.
IMAP	Internet Message Access Protocol	Allows users to access and manage email stored on a mail server.
DNS	Domain Name System	Translates domain names, such as example.com, into IP addresses and provides other DNS records.
DHCP	Dynamic Host Configuration Protocol	Automatically supplies network configuration, commonly including an IP address, subnet mask, gateway and DNS servers.

9.1 TCP and UDP

TCP and UDP are transport-layer protocols, but they work differently. TCP establishes a connection and provides mechanisms for reliable, ordered data delivery. It is commonly used for web traffic, email and file transfers. UDP sends datagrams without establishing a TCP-style connection or guaranteeing delivery and order. It is useful in applications such as real-time voice, video and some online games, where low delay may be important.

9.2 HTTP and HTTPS

HTTP is commonly used for communication between web browsers and web servers. HTTPS is HTTP protected by TLS, which helps provide confidentiality, integrity and server authentication.

Safety tip: HTTPS helps protect the connection, but it does not automatically mean that a website is trustworthy. Users should still check the website address and be careful with personal information.

9.3 DNS and DHCP

DNS helps devices find services using domain names rather than requiring users to remember IP addresses. DHCP automatically assigns network configuration to devices, reducing the need to configure every device manually. For example, when a student connects a laptop to the school network, DHCP may assign an IP address, while DNS helps the laptop locate a website by its domain name.

10. Relationship Between IP Addressing, Subnetting and Protocols

IP addressing, subnetting and protocols work together in network communication.

1. A device receives an IP address and other network settings, possibly through DHCP.
2. The subnet mask or prefix helps the device determine whether a destination is on its local subnet.
3. If the destination is outside the local subnet, the device normally sends the packet to its configured default gateway.
4. IP helps route the packet towards its destination.
5. Transport protocols such as TCP or UDP support communication between applications.
6. Application protocols such as HTTP, DNS and SMTP provide services used by network applications.

Example: When a student opens a website, the device may use DNS to obtain the website's IP address. It then communicates with the server using IP and an appropriate transport protocol. If the website uses HTTPS, HTTP communication is protected using TLS.

11. Class Activity

Activity A: Identify IP Addresses Students should identify which of the following are written in IPv4 notation:

• 192.168.1.10
• 10.0.0.5
• 2001:db8::1
• 172.16.4.20

Activity B: Subnet Calculation A network administrator is given the network 192.168.2.0/24. Students should calculate:

1. The number of host bits.
2. The total number of addresses.
3. The number of usable host addresses in a conventional /24 subnet.
4. The subnet mask.

Activity C: Match the Protocol Students should match each task with an appropriate protocol:

• Automatically assigning IP settings.
• Translating domain names into IP addresses.
• Sending email between mail servers.
• Transferring web pages securely.
• Providing reliable, ordered transport.

12. Summary

An IP address identifies a network interface for communication using the Internet Protocol. IPv4 uses 32-bit addresses written as four decimal octets, while IPv6 uses 128-bit addresses written in hexadecimal notation. Private IPv4 addresses are commonly used within homes, schools and offices. A subnet mask or CIDR prefix identifies the network portion of an address. Subnetting divides a larger network into smaller logical networks, helping with address management and network organisation. Network protocols govern communication. IP supports addressing and routing, TCP provides reliable ordered transport, UDP supports connectionless datagram delivery, DNS resolves domain names, DHCP assigns network settings, and protocols such as HTTP, HTTPS and SMTP support web and email services.

13. Evaluation Questions

Answer the following questions in your notebook.

1. Define an IP address and state three functions of IP addressing.
2. Explain the difference between IPv4 and IPv6.
3. What is the difference between a public IP address and a private IP address?
4. Explain the meaning of a subnet mask and CIDR notation.
5. Define subnetting and state four advantages of subnetting.
6. Calculate the total number of addresses and usable host addresses in a conventional /26 IPv4 subnet.
7. State the functions of TCP, UDP, DNS and DHCP.
8. Differentiate between HTTP and HTTPS.
9. What are SMTP, POP3 and IMAP used for?
10. Explain how IP addressing, subnetting and network protocols work together during communication.

14. Assignment

1. Explain the differences between static and dynamic IP addresses.
2. List the three private IPv4 address ranges and give one example of a private address.
3. A network uses 192.168.5.0/24. Calculate the total number of addresses and usable host addresses.
4. For the subnet 192.168.5.0/26, state the subnet mask, network address, first usable address, last usable address and broadcast address.
5. Write the full meanings and functions of HTTP, HTTPS, FTP, SMTP, POP3, IMAP, DNS and DHCP.
6. Explain why subnetting can be useful in a school computer network.

15. Interactive Online Quiz

Choose the correct option for each question and click Submit Quiz to see your score.

1. How many bits are used in an IPv4 address?

A. 16 bits B. 32 bits C. 64 bits D. 128 bits

2. Which protocol automatically assigns IP configuration to network devices?

A. SMTP B. FTP C. DHCP D. HTTP

3. What is subnetting?

A. Dividing a larger IP network into smaller networks B. Deleting all IP addresses from a network C. Converting a computer into a printer D. Encrypting every file on a computer

4. Which protocol is primarily responsible for translating domain names into IP addresses?

A. TCP B. SMTP C. DHCP D. DNS

5. How many usable host addresses are available in a conventional IPv4 /26 subnet?

A. 30 B. 62 C. 126 D. 254

Quiz Answer Guide

Click to reveal the correct answers

1. B — 32 bits.
2. C — DHCP.
3. A — Dividing a larger IP network into smaller networks.
4. D — DNS.
5. B — 62 usable host addresses.