SS 3 First Term

Lesson objectives

By week's end, candidates should be able to:

1. Name the four TCP/IP layers.
2. Describe encapsulation down the layers.
3. Convert a binary IPv4 address.
4. Calculate usable hosts on a /24.
5. Distinguish DNS from DHCP.

Key vocabulary

• Protocol: agreed rules for exchanging data.
• Encapsulation: adding headers as data moves down layers.
• IP address: a logical host address on a network.
• Subnet mask: a value separating network and host parts.
• DNS: the service mapping names to addresses.
• DHCP: the service leasing addresses automatically.

Common misconceptions

• "The internet and the web are one system." The web is a service on the internet.
• "A /24 network has 256 usable hosts." Two addresses are reserved, leaving 254.

Teacher activities

1. Starter: order the URL-to-page steps.
2. Draw the four-layer table.
3. Model encapsulation with envelopes.
4. Convert 11000000.10101000.00000001.00001010.
5. Work the /24 count.
6. Quiz DNS against DHCP.

Student activities

1. Order the request steps.
2. Copy the layer table.
3. Label four envelopes.
4. Convert the address.
5. Calculate /24 hosts.
6. Match scenarios to services.

Layer	Job	Protocol
Application	user services	HTTP / DNS
Transport	process delivery	TCP / UDP
Internet	addressing and routing	IP
Network access	frames on the link	Ethernet

Practical / learning evidence

ss3_protocols_eze.pdf holds the layer table, a labelled request path, the binary conversion and the /24 count. Success needs 192.168.1.10, 254 hosts and correct layer order.

Resources and preparation

Projector, layer cards and an address worksheet. Offline route: envelope demonstration and hand calculation with the same key.

Assessment for learning

Check layer order and the 254 figure. Award marks for binary place values. Watch for candidates counting 256 hosts.

Inclusion and homework

Supply a table with two cells filled; extend others to a /30 link. Homework: explain why a school needs DHCP.