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GCSE Computer Science > Chapter 5: Networks and the Internet > Flashcards

Chapter 5: Networks and the Internet Flashcards

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1
Q

What is a network?

A

An arrangement of computers or other electronic devices connected to each other

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2
Q

What is a server?

A

A program or powerful computer which manages access to a centralised resource or service in a network

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3
Q

What are the advantages of networks?

A

Allows multiple computers to share devices such as printers, allows files and software to be shared across computers, allows users to log in to their accounts from any computer in the network, provides internet access

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4
Q

What are the disadvantages of networks?

A

Malware can spread, complex and expensive to install, danger of hacking. If the file server stops working users’ files become unaccessible

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5
Q

What is a LAN?

A

A LAN (local area network) is a network that covers a small geographical area such as a school. The hardware is usually owned by the people who run the organisation the network is in

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6
Q

What is a WAN?

A

A WAN (wide area network) is a network that covers a large geographical area and consists of several LANs linked together

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7
Q

What is a client-server network?

A

A network with at least 1 server (the other computers are referred to as clients). The server authenticates the user and then provides access to files

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8
Q

Explain the process in which a client accesses data from a server

A
  1. The client makes a connection to the server with its address
  2. The client makes a service request
  3. If the request is valid, the server will send data or servuces to the client using the address from Step 1
    (sometimes other steps such as authentication are involved)
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9
Q

What is a peer-to-peer network?

A

A network with no centralised servers, in which each computer can act as both a client and a server. This is how torrenting works

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10
Q

What is a network topology?

A

A way in which the connections between networked computers are arranged

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11
Q

Describe the bus network topology

A

A single cable which each device is connected to, with a terminator at the end (which absorbs signals and prevents them from bouncing back). Only one signal can be sent at a time, and the CSMA/CD algorithm can be used to handle multiple simultaneous messages

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12
Q

Describe the ring network topology

A

A network in which cables connect one device to another in a closed loop. Each device has an input and an output cable.

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13
Q

How does CSMA/CD work?

A
  1. Check if bus is busy
  2. If not busy, send a message, otherwise repeat Step 1
  3. Check to see if message received correctly
  4. If not received successfully, go to Step 5, otherwise go back to Step 1
  5. Wait random amount of time and go back to Step 1
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14
Q

What are the advantages of the bus topology?

A

Cheap to install (1 cable only), easy to add new devices

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15
Q

What are the disadvantages of the bus topology?

A

Whole network fails if cable cut, difficult to identify faults on cable, gets slower as more devices are added, all devices receive all data sent (security risk)

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16
Q

What are the advantages of the ring topology?

A

No collisions: Adding more devices does not slow the network down, easy to add new devices

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17
Q

What are the disadvantages of the ring topology?

A

Whole network fails if any cable or device stops working, adding a device temporarily shuts down the network, difficult to identify faults, more cables, more expensive

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18
Q

What is a modem?

A

A modem enables a computer to connect to the internet over a telephone line. A modem converts digital signals from a computer to analogue signals that are then sent down the telephone line. A modem on the other end converts the analogue signal back to a digital signal which another computer can understand.

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19
Q

What is a hub?

A

A hub broadcasts data to all devices on a network. This can use a lot of bandwidth as it results in unnecessary data being sent - not all computers might need to receive the data.

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20
Q

What is a router?

A

A device that can form a LAN by connecting devices within a building. It also makes it possible to connect different networks together. Homes and businesses use a router to connect to the internet. A router incorporates the capability of hubs, bridges and switches.

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21
Q

What is a switch?

A

A switch performs a similar role to a hub and a bridge but is more powerful. It stores the MAC addresses of devices on a network and filters data packets to see which devices have asked for them.

22
Q

What is a bridge?

A

A bridge is used to connect two separate LAN networks. A computer can act as a bridge through the operating system.

23
Q

What is the difference between fibre-optic and coaxial cables?

A

Coaxial cables use copper to conduct electrical signals. Fibre-optic cables use glass to carry light signals. They are faster than coaxial cables and have less signal attenuation.

24
Q

What is a protocol?

A

A set of rules that govern how communications on a network should be formatted and what data they should include

25
Q

How do wireless connections work?

A

Devices transmit and receive radio signals (infrared and microwaves can be used over a short distance)

26
Q

What are the advantages of wireless connectivity?

A

Cheaper, no cables required, devices don’t have to be tethered to a certain point, allows new users to use their device without buying a new cable, compatible with phones

27
Q

What are the disadvantages of wireless connectivity?

A

Slower, interference from other wireless devices and walls, data needs to be encrypted to prevent eavesdropping

28
Q

What details could a protocol contain?

A

Destination address, data route, what to do if data isn’t received correctly, how the data is to be formatted/sequenced, how the speed of the sender and the receiver can be synchronised

29
Q

What is SMTP?

A

Simple Mail Transfer Protocol (used when sending email through the internet). It details the format in which messages are sent, and what commands email servers should understand

30
Q

What is POP3?

A

Post Office Protocol 3 (used when retrieving email from a server). Clients using POP3 connect to the server, download messages and then delete them from the server

31
Q

What is IMAP?

A

Internet Message Access Protocol (used when retrieving email from a server). IMAP leaves messages on a server until a user deletes them, allowing emails to be accessed with multiple clients

32
Q

What is ethernet?

A

A family of protocols used in wired LANs, which regulate how data is sent, error checking, data speed, as well as physical things such as cable type

33
Q

What is Wi-Fi?

A

A protocol that sets out how data is transmitted in wireless LANs

34
Q

What is a checksum?

A

An error detection technique in which data is run through a mathematical formula which produces a number. This number is sent along with the data. On the other side, the other computer applies the same formula and checks to see if the checksums are the same. If they’re not, the data has been corrupted

35
Q

What is TCP?

A

A protocol that provides a reliable connection between computers (meaning all the data is sent correctly). TCP incorporates checksums and specifies that the receiving computer must send acknowledgements that it received the data correctly. It also allows the receiver to tell the sender to slow down the transmission rate, and ensures that data contains no duplicates

36
Q

What is TCP/IP?

A

A protocol stack (a set of protocols that work together) named after the 2 most important protocols in the stack. The protocols work in a hierarchical set of layers, where each layer deals with a particular function of the network. Data passes down the stack when sending and up the stack when receiving

37
Q

What is the application layer?

A

The layer which interacts with the user to provide access to services/data sent across a network. Includes HTTP, FTP and email protocols

38
Q

What is a packet?

A

A small quantity of data being sent through a network. Each packet’s header contains the addresses of both the sender and the receiver, the number of packets being sent, and the position of the packet in the complete message. The receiver uses this data to assemble the packets into a message

39
Q

What layers are in TCP/IP?

A

Application, Transport, Internet, Link

40
Q

What is the transport layer?

A

The layer that manages end-to-end communication across a network. Includes TCP and UDP

41
Q

What is the internet layer?

A

The layer that manages sending data between networks, which is known as routing. Includes IP (Internet Protocol)

42
Q

What is the link layer?

A

The layer that controls the transmission of data to/from a local network

43
Q

What is HTTP?

A

The protocol used when sending/receiving data between web browsers and web servers. It covers how data should be formatted and what commands the browser should understand. HTTPS is like HTTP but encrypted and more secure.

44
Q

What is FTP?

A

File Transfer Protocol: Used when transferring files over a network that uses TCP (e.g. uploading/downloading files)

45
Q

What is IP?

A

Internet Protocol: Manages the addressing system used to identify individual computers on the internet. IP also manages splitting data into packets

46
Q

What is an IP address?

A

An address assigned to an internet-connected device that allows data to be routed to it. IPv6 has more possible addresses than IPv4

47
Q

What aspects does network security cover?

A

Confidentiality, availability to users (preventing DoS attacks), correctness

48
Q

How can networks/data be protected?

A

Access control, firewalls, physical security [COMPLETE LATER]

49
Q

Why is network security important?

A

Data is required for the running of the organisation, data can be financially valuable, user data can be private and could lead to identity theft if leaked

50
Q

What does a firewall do?

A

Sits between a LAN and the internet and uses a set of rules to determine whether data should be allowed to pass between the networks (e.g. stop certain protocols from being used, block hacking attempts, block certain websites)

GCSE Computer Science (6 decks)

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