ACARA Digital Technologies Years 7–8 — Wired and Wireless Networks Hangman

The 73 key terms

1network

A group of digital systems connected together so they can share data, files, printers and an internet connection. Each connected device is called a node.

2data transmission

The sending of data, such as text, images, audio or video, from a sender device to a receiver device.

3internet

The global network of networks that connects computers worldwide. The World Wide Web is one service that runs on it, alongside email, streaming and online games.

4client-server

A client, like your browser, sends a request for data and a server stores that data and sends a response back.

5LAN vs WAN

A LAN connects devices in one small area like a home or school. A WAN connects many LANs over a large distance. The internet is the largest WAN.

6network interface

The internal part of a device that lets it send and receive data on a network, using an Ethernet port for wired links or a wireless adapter for Wi-Fi.

7network switch

A device that connects computers on the same network and sends data only to the device it is meant for, using its ports. A router links different networks.

8router

A device that directs data between networks, such as joining a home LAN to the internet and choosing the path data packets take. A home Wi-Fi router also shares the connection wirelessly.

9modem

A device that converts signals so a local network can connect to an internet service provider (ISP), such as over an NBN connection. A router then shares that connection.

10wireless access point

A device that connects to a wired network and broadcasts a Wi-Fi signal so wireless devices can join the network.

11data path

The route data takes across a network, passing through devices like a router and ISP from the sender to the receiver (a server), then the reply travels back along the route.

12wired transmission

Sending data as signals along a physical cable, such as a USB, Ethernet or fibre optic cable. Wired links are usually fast and reliable.

13Ethernet cable

A cable with an RJ45 plug that carries data as electrical signals along twisted pairs of copper wire between a device and a switch or router.

14fibre optic cable

A cable that carries data as pulses of light along thin glass or plastic strands, giving very fast transfer over long distances with no electrical interference.

15attenuation

The weakening of a signal as it travels along a cable. Copper cables have a length limit because of it, while fibre can go much further. Repeaters boost the signal.

16wireless transmission

Sending data as radio signals through the air with no cables, like Wi-Fi, Bluetooth and mobile data. Range and interference can weaken the signal.

17Wi-Fi

A wireless network technology that uses radio waves to connect devices to a router or access point, usually by joining a network name and password on the 2.4 GHz or 5 GHz band.

18mobile network

A network that sends data by radio between a device and a nearby phone tower (cell), so it works over wide areas without Wi-Fi.

19Bluetooth

A wireless technology that sends data between two nearby paired devices, such as a phone and headphones, over a short range.

20bandwidth

The amount of data a network connection can carry in a given time, usually measured in Mbps. Shared by all users, so more people or video streaming means less speed each.

21latency

The delay between sending data and it arriving, measured in milliseconds (ms). It is not the same as bandwidth, which is how much data can be sent at once. Low latency feels fast.

22Wi-Fi range

How far a Wi-Fi signal reaches. It gets weaker with distance and walls, and interference from other devices on crowded channels can slow or drop your connection.

23wired speed

Wired connections are usually faster and steadier than wireless, because the signal travels in its own cable and is not shared through the air.

24reliability

How steadily a connection stays working. Wired is usually more reliable as interference affects it less, while wireless signals can drop out.

25wireless security

Wired data stays in the cable, but wireless signals travel through the air where anyone in range can try to pick them up, so they need a password and encryption.

26WPA3

The newest Wi-Fi security standard. With a strong password it scrambles data in the air so outsiders can't read it. WPA2 is the older version. Open networks have no protection at all.

27cost and installation

Wired networks need cables, ports and installation work, while wireless needs less cabling but may need more access points to cover a large area.

28mobility

Wireless devices like phones and tablets can move around and join a network easily, while wired devices like desktop computers are tied to a fixed cable connection point.

29wired vs wireless

Wired links are usually faster, more reliable and more secure. Wireless links are more mobile and convenient. Choose the one that best suits the situation.

30choose a network type

Name the needs (speed, reliability, security, cost, mobility), match them to wired, wireless or mobile, then justify the choice using the word because.

31protocol

An agreed set of rules that devices follow so they can communicate, like HTTP for web pages. Both devices must use the same protocol to understand each other.

32IP address

A unique number that identifies a device on a network, like a postal address, so data knows where to go. IPv4 looks like 192.168.1.5.

33IPv4 address

32 bits written as four denary numbers from 0 to 255 separated by full stops, such as 190.0.5.20. Each number is a group of 8 bits.

34TCP/IP

The pair of protocols the internet runs on. IP addresses and routes packets. TCP splits data into packets, puts them back in order and checks they all arrived.

35HTTP

Hypertext Transfer Protocol: the set of rules a browser and web server use to request and send web pages. It is the default protocol for the web and is used only for web pages.

36HTTP request and response

The browser sends an HTTP request asking for a page. The web server sends back an HTTP response with the page's HTML, or an error such as 404 page not found.

37HTTPS

HTTP plus SSL/TLS encryption. Plain HTTP sends readable text that can be intercepted; HTTPS scrambles data so intercepted data can't be read, and a certificate shows the site is genuine.

38packet

A small chunk of data with the sender, destination and order number attached. Packets travel a network by different routes and are put back in order at the destination.

40header, payload, trailer

The three parts of a packet, in order: the header (start) holds addresses and packet number, the payload (middle) holds the data, the trailer (end) marks the packet's end.

41packet header

The first part of a packet. It holds control information: the destination address, the originator's address and the packet number, used to deliver and reassemble the packet.

42destination address

The address in a packet header of the device the packet must be delivered to. Routers read it to choose where to send the packet. It is usually an IP address.

43packet number

A number in the packet header showing the packet's position in the whole message (e.g. packet 3 of 10), so packets that arrive out of order can be put back in the right order.

44payload

The part of a packet that carries the actual data being sent, such as a piece of a file or message. The header and trailer are not payload.

45packet trailer

The last part of a packet. It marks where the packet ends and can hold error checking information, so the receiving device can check the data arrived correctly.

46packet switching

Data is split into packets that are sent separately, each routed on its own from router to router, then joined back together in the right order at the destination.

47routing

A router reads each packet's destination address in its header and picks the next router to send it to, so every packet's route is decided one step at a time.

48different routes

Packets from one message can take different routes because each router picks the best available path at that moment, avoiding busy or broken links. Routes may take different lengths of time.

49redundant route

A spare path between devices. If one link or router fails, packets are sent another way so data keeps flowing. It costs more because extra cables and routers are needed.

50packets arrive out of order

Packets take different routes, so they may reach the destination in a different order from the one sent, e.g. packet 5 before packet 4. Order is not guaranteed.

51reordering packets

After the last packet arrives, the receiving device uses the packet numbers in the headers to put the packets in the right order and joins the payloads to rebuild the message.

52packet switching steps

Data is split into numbered packets, routers pick each packet's route, packets may arrive out of order, then they are reordered to rebuild the data once the last packet arrives.

53data integrity

Data has integrity when it arrives complete (nothing missing or extra) and correct (nothing changed) compared with what was sent.

54error detection

Checking received data, because it can be damaged in transit and the receiver cannot see the original. Spotting the error is the first step to fixing it.

55interference

Unwanted disturbance to a signal, such as electrical noise or crosstalk, that damages data as it travels and can cause bits to be lost, gained or changed.

56data loss

When some bits or bytes that were sent never arrive, so the message that is received is shorter than the one that was sent.

57data gain

Data gain is when extra bits or bytes that were not sent are added to the data, so the message arrives longer than it was sent. It is a type of transmission error.

58data change

Bits arrive altered, such as a 0 flipping to a 1, so the same amount of data arrives but with wrong values. Comparing sent and received bits shows it.

59compare sent and received

Compare the data sent with the data received. Fewer bits or characters means loss, extra ones means gain, and the same length with different values means change.

60missing packet

A gap in the packet numbers received, like 1, 2, 4, 5, shows a packet is missing. The receiver knows the message is incomplete and can ask for a resend.

62parity bit

One extra bit added to a group of bits (such as 7 data bits) so the total number of 1s follows a rule, even or odd, agreed by sender and receiver. It is used to detect errors.

63even parity

A parity bit is added so the total number of 1s in the byte, including the parity bit, is even. Odd count of 1s in the data gives parity bit 1; even count (even 0) gives 0.

64count the 1s

Count the 1s in the 7 data bits, then set the leftmost parity bit to 0 or 1 so the total number of 1s in the whole 8-bit byte matches the agreed rule (even or odd).

65parity check

The receiver counts the 1s in the whole received byte, parity bit included. If the count breaks the agreed even or odd rule, an error has occurred and is detected.

66even number of bits change

A single parity check misses an error when an even number of bits change, because the count of 1s keeps the same parity. It also cannot show which bit is wrong.

67checksum

A value calculated from a block of data by a set rule and sent with it. The receiver repeats the calculation and compares the results. If they differ, an error occurred.

68recalculate and compare

The receiver recalculates the checksum from the received data and compares it with the one sent. Match means no error detected; mismatch means error, so resend is requested.

69echo check

The receiver sends a copy of the received data back to the sender, who compares it with the original. A match means no error was detected; a mismatch means the data is sent again.

70positive acknowledgement

A message sent by the receiver to tell the sender that data arrived without error. Often written ACK. It is sent only after the error check passes, so the sender can send the next data.

71negative acknowledgement

A message (NAK) the receiver sends to the sender when the error check fails, telling it the data arrived with an error so the sender must resend the same data.

72timeout

The set time a sender waits for an acknowledgement after sending data. If none arrives in time, it assumes the data was lost and resends it.

73ARQ

Automatic repeat query: the receiver checks data for errors and replies. If the data is bad or no reply arrives, the sender automatically resends it until it is received correctly.

75error detection method

Parity, parity block, checksum and echo check find errors in transmission; a check digit finds them at data entry; ARQ asks for a resend. Each sends different extra data.

76split, send, check, resend, reassemble

Data is split into numbered packets, sent over wired or wireless links, checked for errors, resent if needed, then reassembled in order so it arrives complete and correct.