Computing · Secondary 4 · Computer Networks and Communication · Semester 1

IP Addressing and DNS

Understanding IPv4 and IPv6 addressing schemes and the role of the Domain Name System (DNS).

• MOE Syllabus Outcomes
• MOE: Computer Networks - S4
• MOE: Network Infrastructure - S4

About This Topic

IP addressing identifies devices on a network, ensuring data packets reach the correct destination. IPv4 uses 32-bit addresses in dotted decimal format, like 192.168.1.1, supporting about 4 billion unique addresses. However, rapid internet growth caused address exhaustion, leading to IPv6 adoption with 128-bit hexadecimal addresses that provide virtually unlimited space. Students examine subnetting in IPv4 and the expanded features of IPv6, such as built-in security and auto-configuration.

The Domain Name System (DNS) resolves human-readable domain names, such as www.moe.gov.sg, into IP addresses through a hierarchical server structure. In the MOE Secondary 4 Computing curriculum, under Computer Networks and Communication, this topic builds foundational knowledge of network infrastructure. Students analyze how DNS queries work step-by-step, from root servers to authoritative name servers, and connect it to everyday web browsing.

Active learning suits this topic well. Students configure mock networks or trace real DNS lookups, observing failures like expired caches. These experiences clarify abstract processes, strengthen troubleshooting skills, and make theory relevant to real-world scenarios.

Key Questions

1. Explain the necessity of IP addresses for identifying devices on a network.
2. Differentiate between IPv4 and IPv6 and the reasons for the transition.
3. Analyze how DNS translates human-readable domain names into IP addresses.

Learning Objectives

• Compare the structure and address formats of IPv4 and IPv6, identifying key differences.
• Explain the hierarchical structure of DNS and the function of each server type in resolving domain names.
• Analyze the process of a DNS lookup query, tracing the path from client to authoritative name server.
• Evaluate the necessity of IP addressing for device identification and data routing on computer networks.
• Demonstrate the relationship between domain names and their corresponding IP addresses.

Before You Start

Basic Computer Network Concepts

Why: Students need a foundational understanding of what a network is and how devices communicate before learning about specific addressing schemes.

Data Representation (Binary and Hexadecimal)

Why: Familiarity with binary and hexadecimal number systems is essential for comprehending the structure of IPv4 and IPv6 addresses.

Key Vocabulary

IP Address	A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
IPv4	The fourth version of the Internet Protocol, using a 32-bit address scheme that supports approximately 4.3 billion unique addresses.
IPv6	The latest version of the Internet Protocol, using a 128-bit address scheme that provides a vastly larger number of unique addresses.
DNS (Domain Name System)	A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network.
DNS Resolver	A DNS client that initiates requests for DNS data, typically residing on the user's computer or local network.
Authoritative Name Server	A DNS server that holds the official records for a domain and is the ultimate source of information for that domain's IP address.

Watch Out for These Misconceptions

Common Misconception

IPv6 is just a longer version of IPv4 with no real differences.

What to Teach Instead

IPv6 offers expanded address space, simplified headers, and mandatory IPsec, unlike IPv4. Hands-on configuration in simulators shows these benefits, as students compare packet structures and resolve dual-stack issues through peer debugging.

Common Misconception

DNS directly stores all domain names on one central server.

What to Teach Instead

DNS uses a distributed hierarchy of servers for scalability. Tracing queries in tools like dig reveals delegation steps; group discussions help students map their initial flat model to the actual tree structure.

Common Misconception

IP addresses change every time you connect to the internet.

What to Teach Instead

Public IPs may change with dynamic assignment, but local ones often stay static. Network simulations let students assign and test both types, clarifying DHCP leases via observed continuity.

Active Learning Ideas

Simulation Lab: IPv4 Subnetting Challenge

Provide students with a class C network address. In pairs, they calculate subnets for different departments, assign host ranges, and verify with online calculators. Discuss validity as a group.

30 min·Pairs

DNS Trace Activity: Packet Capture

Use Wireshark to capture DNS queries for school websites. Students identify query types, response times, and IP mappings in small groups. Compare IPv4 and IPv6 resolutions.

45 min·Small Groups

Role-Play: Network Device Assignment

Assign roles as routers, clients, and DNS servers. Groups simulate IP requests and resolutions using printed cards. Whole class debriefs transition challenges from IPv4 to IPv6.

35 min·Small Groups

IPv6 Configuration Drill

In individual setups with Cisco Packet Tracer, students enable IPv6 on virtual routers and pings devices. Note auto-configuration advantages over IPv4 DHCP.

40 min·Individual

Real-World Connections

• Network engineers at telecommunications companies like Singtel use their understanding of IP addressing and DNS to manage vast networks, ensuring millions of users can access the internet reliably and efficiently.
• Web developers and system administrators rely on DNS to point domain names like example.com to the correct web servers, making their websites accessible globally. They troubleshoot DNS issues to resolve website downtime.
• Cybersecurity analysts investigate network traffic, analyzing IP addresses to identify malicious actors or unauthorized access attempts. Understanding IP routing is crucial for tracing the origin of threats.

Assessment Ideas

Quick Check

Present students with a list of IP addresses (e.g., 192.168.1.10, 2001:0db8:85a3:0000:0000:8a2e:0370:7334). Ask them to identify which is an IPv4 address and which is an IPv6 address, and to briefly state one reason for their choice.

Discussion Prompt

Pose the question: 'Imagine the internet without DNS. Describe in two to three sentences the challenges users would face when trying to visit websites.' Facilitate a brief class discussion on their responses.

Exit Ticket

On a slip of paper, ask students to write down: 1) One key difference between IPv4 and IPv6. 2) The primary role of a DNS authoritative name server. 3) One step in the DNS lookup process.

Frequently Asked Questions

How does DNS translate domain names to IP addresses?

DNS starts a recursive query from the client's resolver to root servers, then TLD servers, and finally authoritative servers holding the record. Caching reduces repeat queries. Students benefit from diagramming this path, as it reveals why some sites load slowly during outages.

Why is Singapore transitioning to IPv6?

IPv4 shortages force NAT usage, complicating services. IPv6 enables direct end-to-end connectivity for IoT growth. In class, explore Singtel's rollout data; it ties to national digital plans and prepares students for future networks.

How can active learning help teach IP addressing and DNS?

Tools like Packet Tracer let students build networks, assign IPs, and query DNS, turning theory into practice. Group traces of real queries reveal hierarchies and errors. This boosts engagement, as students debug issues collaboratively, improving retention over lectures.

What are key differences between IPv4 and IPv6?

IPv4 has 32 bits, checksums, and optional fragmentation; IPv6 uses 128 bits, no checksums, and router-only fragmentation. Broadcasts become multicasts in IPv6. Comparison tables and simulations clarify why IPv6 supports more devices without workarounds.