Year 10 · Computer Science · Spring 1

Hardware · Lesson 5 of 5

Network hardware and the exam questions

Exam practice3.4 Network hardware

Year 10 · Computer Science · Hardware · Lesson 5 of 5

You will learn to

  • State what a network interface card (NIC) does.
  • Describe a MAC address: 48 bits, written as 12 hex digits, set by the manufacturer.
  • Explain what an IP address is for, and compare static with dynamic, and IPv4 with IPv6.
  • Describe the role of a router.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Success criteria

You have got it when you can say:

  • I can split a MAC address into the manufacturer part and the serial number part.
  • I can say that IPv4 uses 32 bits and IPv6 uses 128 bits.
  • I can explain how a router uses IP addresses to forward packets.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Retrieval starter

Questions from before. Write your answers, then show them.

  1. Last lesson

    A solid-state drive…

    A Has no moving partsB Uses a laserC Uses spinning platters

    A. Has no moving parts

  2. Last unit

    XOR gives 1 when…

    A Neither input is 1B Exactly one input is 1C Both inputs are 1

    B. Exactly one input is 1

  3. Earlier this year

    A 10 × 10 image at 8 bits per pixel takes…

    A 800 bits = 100 bytesB 8,000 bitsC 80 bytes

    A. 800 bits = 100 bytes

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Key words (1 of 2)

Control unit
Manages the fetch–decode–execute cycle and sends control signals.
NIC
Network interface card: the hardware that connects a device to a network.
MAC address
A unique 48-bit address given to a NIC at manufacture, written in hex.
IP address
An address given to a device on a network so data can be sent to it.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Key words (2 of 2)

Router
A device that forwards packets to their destination and connects a local network to the internet.

The explanation · step 1 of 4 · part 1 of 3

NIC and MAC address

A network interface card (NIC) is the hardware that lets a device connect to a network, by cable or by Wi-Fi. Today it is usually built into the main board.

Every NIC has a MAC address (media access control address). It is assigned when the NIC is manufactured and is unique to that device.

A MAC address is 48 bits, written as 12 hexadecimal digits in 6 pairs, e.g. `00:1A:2B:3C:4D:5E`.

The explanation · step 1 of 4 · part 2 of 3

NIC and MAC address (continued)

The first half is the manufacturer code (who made it). The second half is the serial code (which device it is).

e.g.Example
MAC address 00:1A:2B:3C:4D:5E Manufacturer code: 00:1A:2B Serial code: 3C:4D:5E 48 bits gives 2⁴⁸ = 281,474,976,710,656 possible addresses.

The explanation · step 1 of 4 · part 3 of 3

NIC and MAC address (continued)

?Why?

Hex is used because 48 binary digits are too long for people to read. Each hex digit stands for 4 bits, so 12 hex digits = 48 bits.

The explanation · step 2 of 4 · part 1 of 3

IP address: IPv4 and IPv6

An IP address identifies a device on a network, and lets data be sent to the right place across the internet. It is given to the device by the network it joins, so it can change.

IPv4: 32 bits, written as four denary numbers from 0 to 255, separated by dots, e.g. `192.168.1.20`. This gives 2³² = 4,294,967,296 addresses.

IPv6: 128 bits, written as eight groups of four hex digits, separated by colons, e.g. `2001:0db8:85a3:0000:0000:8a2e:0370:7334`.

The explanation · step 2 of 4 · part 2 of 3

IP address: IPv4 and IPv6 (continued)

IPv6 was created because the world was running out of IPv4 addresses. Every phone, laptop and smart device needs one.

e.g.Example
IPv4 192.168.1.20 in binary, 8 bits per number: 11000000.10101000.00000001.00010100 IPv6 groups of zeros can be shortened with :: 2001:0db8:85a3:0000:0000:8a2e:0370:7334 → 2001:db8:85a3::8a2e:370:7334 Try it in the toy: type 192.168.1.20 in the IPv4 tab, and the long IPv6 address above in the IPv6 tab, to check both answers. Then open the MAC address tab and compare the parts.

The explanation · step 2 of 4 · part 3 of 3

IP address: IPv4 and IPv6 (continued)

!Watch out

A MAC address is fixed to the hardware. An IP address belongs to the connection and can change. A phone keeps its MAC address but gets a new IP address on school Wi-Fi.

There is something to try for this step in the IGCSE library.

The explanation · step 3 of 4 · part 1 of 2

Static and dynamic IP addresses

A static IP address is permanent. It does not change each time the device connects.

A dynamic IP address is assigned automatically each time the device connects, and can be different next time. It is given out by a server, often the router.

Static addresses are used for servers (such as a website or a school printer), so other devices can always find them. Dynamic addresses suit ordinary users.

The explanation · step 3 of 4 · part 2 of 2

Static and dynamic IP addresses (continued)

StaticDynamic
Changes?NoCan change each time
Good forWeb servers, printers, remote access, CCTVPhones, laptops, home devices
AdvantagesAlways the same, so easy to find; reliable for hostingAutomatic; addresses are reused, so fewer are needed; usually cheaper
DisadvantagesMust be set up and managed; often costs more; easier to targetAddress can change, so not good for hosting a server

The explanation · step 4 of 4 · part 1 of 2

The router

A router sends data packets to their destination. It reads the destination IP address in each packet's header and forwards it on the best route.

It connects a local network to the internet, for example a home or school network to the Internet Service Provider.

It also assigns IP addresses (dynamic, private ones) to the devices on the local network.

The explanation · step 4 of 4 · part 2 of 2

The router (continued)

e.g.Example
At home, your laptop gets 192.168.1.20 from the router. You visit a website. The router sends your packets out to the internet, and passes the replies back to your laptop and not to your sister's phone.
?Why?

This links back to topic 2: packet switching only works because routers read headers and choose routes.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Try it: Check an IP address

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Quick quiz · 1 of 3

A MAC address is…

  1. A The name of a website
  2. B The fixed hardware address of a network card
  3. C Given out by the router each time

B. The fixed hardware address of a network card

The IP address can change; the MAC is burnt in at the factory.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Quick quiz · 2 of 3

The register that holds the address of the next instruction is the…

  1. A Accumulator (ACC)
  2. B Memory address register (MAR)
  3. C Program counter (PC)

C. Program counter (PC)

PC points at the next instruction. MAR holds the address being used right now.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Quick quiz · 3 of 3

Which bus carries the actual data?

  1. A Address bus
  2. B Control bus
  3. C Data bus

C. Data bus

Address bus: where. Data bus: what. Control bus: when and which way.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Exit ticket

Answer on paper before you go. Then check.

  1. The ALU does…

    A Fetching instructionsB Arithmetic and logicC Storing files

    B. Arithmetic and logic Add, subtract, compare. The control unit does the fetching and decoding.

  2. Cache is…

    A Small, fast memory beside the CPU for recently used dataB The hard diskC The program counter

    A. Small, fast memory beside the CPU for recently used data Bigger cache means fewer slow trips to RAM.

Year 10 · Computer Science · Hardware · Lesson 5 of 5

Homework and the challenge

Homework

The CS 3 quiz.

End-of-unit challenge

End-of-unit test: past-paper questions on topic 3.