Edexcel GCSE Computer Science

5: Communication and the Internet

Revision tools
You can print this page for a quick reference guide or you can use the tools below to create printable test sheets
5.1.1: understand why computers are connected in a network
Communication and the Internet
KeywordDefinition
Computerhardware and software making up an individual system
Hardwarephysical devices that can be shared on a network such as printer or backup drive
Networkmultiple computers connected together to share data and resources
Remote administrationthe process of installing software, updates or changing user settings via a network rather than sitting in front of a computer
Resourceshardware and software that can be shared across a network (e.g. printer and shared folders)
Softwareprograms that can be installed on multiple computers in a network
5.1.2: understand the different types of networks (LAN, WAN) and usage models (client-server, peer-to-peer)
Communication and the Internet
KeywordDefinition
Clienta computer (e.g. phone, tablet, desktop) that requests data from a server. It might not always be connected to the network and it shouldn't be trusted with sensitive data as it might be used by a hacker
Local Area NetworkA network made up of computers connected together over a small area such as a school or office
Peera computer connected to a network that talks directly to other connected computers without needing to go through a server.
Servera dedicated computer that listens for requests from multiple clients. It has a permanent network connection and is often trusted to store sensitive data.
Usage modela way that computers connected to a network communicate with each other (e.g. client-server or peer-to-peer)
Wide Area NetworkA network made up of multiple smaller networks connected together in multiple physical locations
5.1.3: understand wired and wireless connectivity
Communication and the Internet
KeywordDefinition
Connectivitythe way that computers are connected together (e.g. wired / wireless)
Copper wirea cheap physical connection between devices that uses electrical signals to transmit data.
Fibre opticphysical connection between devices that uses light instead of electricity to transmit data at high speeds and over long distances
Wireda method of connecting devices on a network using a physical link (e.g. fibre optic or copper wire)
Wirelessa method of connecting devices on a network using radio signals to transmit data (e.g 3G or WiFi)
5.1.4: understand that network data speeds are measured in bits per second (Mbps, Gbps)
Communication and the Internet
KeywordDefinition
BitThe smallest possible quantity of binary data: a single 1 or 0
bpsA measure of data transmission speed meaning the number of bits that are sent / received every second
Gbpsdata transmission speed meaning 1,000,000,000 bits per second
Kbpsdata transmission speed meaning 1,000 bits per second
Mbpsdata transmission speed meaning 1,000,000 bits per second
Transmissionsending or receiving data
5.1.5: understand the role of and need for network protocols (Ethernet, Wi-Fi, TCP/IP, HTTP. HTTPS, FTP, email (POP3, SMTP, IMAP))
Communication and the Internet
KeywordDefinition
Encryptedtype of connection that uses an algorithm to keep data secure so it can only be understood using a password
Ethernetnetwork protocol for transmitting data using copper cables.
FTPunencrypted network protocol used to transfer files from one computer to another
HTTPunencrypted network protocol for transmitting web pages and resources over the Internet
HTTPSencrypted network protocol for transmitting web pages and resources over the Internet
IMAPnetwork protocol used to view email messages stored on a server
POP3network protocol used to download email messages to your computer
Protocolset of rules that devices must follow in order to communicate over a network
SFTPencrypted network protocol used to transfer files from one computer to another
SMTPnetwork protocol used to send email messages
TCP/IPnetwork protocol used to connect computers to the Internet and to allow reliable transmission of data
Unencryptedtype of connection that sends data in a way that could potentially be intercepted and understood without needing a password
Wi-Finetwork protocol for transmitting data using radio waves
5.1.6: understand that data can be transmitted in packets using layered protocol stacks (TCP/IP)
Communication and the Internet
KeywordDefinition
ApplicationTop layer of the TCP/IP protocol stack where programs request and process data over a network
Data Link Layeranother name for the Network Access layer of the TCP/IP protocol stack
Ethernet and WiFiexamples of protocols which operate at the Network Access Layer of the TCP/IP stack to control how individual bits and bytes are transmitted
Headerdata inside a packet that identifies where the data is from, where it's going to and order that the packet needs to be placed in to be reassembled back into the original file or message.
HTTP and FTPexamples of protocols which operate at the application layer of the TCP/IP stack to send / receive web pages and files
Internet3rd highest layer of the TCP/IP protocol stack where destination and source IP addresses are added to data packets which are then routed to the right place across the network
IPThe part of TCP/IP that allows packets to be delivered to the right place over a large network like the Internet using destination and source addresses
MAC and IPtypes of network addresses which are used at the Internet layer of the TCP/IP stack to ensure packets of data get to the right destination
Network AccessBottom layer of the TCP/IP protocol stack which controls how individual bits and bytes are transmitted across wires, fibre optic cables or radio waves
Network Layeranother name for the Internet layer of the TCP/IP protocol stack
Packetssmall chunks of data (typically 64KB) that contain part of a file or message to be transmitted over a network
Protocolset of rules that devices must follow in order to transmit a certain type of data over a network
Stackmultiple layers of protocols that work independently in order to make a network work
TCPThe part of TCP/IP that splits data into a sequence of packets that can be reliably transmitted over a network
TCP and UDPexamples of protocols which operate at the Transport layer of the TCP/IP stack to transmit packets of data reliably or quickly
Transport2nd highest layer of the TCP/IP protocol stack where data is split into packets which are sent and reassembled reliably and in order.
5.1.7: understand characteristics of network topologies (bus, ring, star, mesh)
Communication and the Internet
KeywordDefinition
Busnetwork topology where computers are each connected to a main cable or link
Collisionhappens when two computers try to send data at the same time over the same wire or link, resulting in data having to be sent again in order not to be corrupted
Meshnetwork topology where computers are all directly connected to each other without a hub or server
Nodean individual computer connected to a network
Ringnetwork topology where computers are connected so that data only flows in one direction round a circle
Starnetwork topology where computers are individually connected to a central hub or server
Terminatorspecial connector placed at the end of a bus topology network cable used to stop signals bouncing back down the bus
Tokenspecial data packet passed around a ring topology network indicating which computer's turn it is to send data
Topologythe way that computers are arranged and connected together in a network
5.2.1: understand the importance of network security and be able to use appropriate validation and authentication techniques (access control, physical security and firewalls)
Communication and the Internet
KeywordDefinition
Access controlthe process of granting or denying specific privileges to users to control what they can and can't do
Authenticationthe process of checking that the password a user enters is the right one, so that they can access a computer system.
Firewallsthe process of granting or denying access to network traffic from specific network addresses or protocols
Network securitythe process of using physical security, firewalls, access control, validation and authentication to only allow access to a network or computer to certain people or devices
Physical securitythe process of making it difficult to access the hardware components inside a computer system
Validationthe process of checking that a password meets certain rules (e.g. contains capital and lowercase letters and is over a certain length of characters)
5.2.2: understand security issues associated with the cloud and other contemporary storage
Communication and the Internet
KeywordDefinition
Abstractionhiding unnecessary detail (e.g. what type of device data is actually stored on within a cloud computing service) in order to focus on what's important (e.g. data can be saved without needing a local storage device)
Always connecteda feature of cloud storage which makes it easier for both users and hackers to access compared to local storage devices
Cloudusing networked servers to provide storage and software services
Contemporary storageusing cloud storage services like Dropbox or Google Docs to replace local storage with virtualised network storage
Credentialsusername and passwords that provide access to a file or service
Encryptiona feature of cloud storage which makes it more secure because data can only be accessed with the right credentials
Virtualisationa type of abstraction where the true nature of a physical device is hidden from the user to share resources or simplify management. E.g. one physical server might be split into multiple virtual servers: one for each customer or web site that uses it.
5.2.3: understand different forms of cyberattack (based on technical weaknesses and behaviour) including social engineering (phishing, shoulder surfing), unpatched software, USB devices, digital devices and eavesdropping
Communication and the Internet
KeywordDefinition
DDOSa type of computer attack where a computer or network service is shut down due to being overwhelmed by a high volume of traffic distributed from a large number of computers
Digital devicessmall computers (e.g Raspberry Pi) which can be connected to a network then hidden away whilst they harvest sensitive data
DOSa type of cyber attack where a computer or network service is shut down due to a being overwhelmed by a high volume of traffic from one computer
Eavesdroppingthe process of inspecting network traffic from other devices in order to find sensitive data like usernames and passwords
Phishinga form of cyberattack where users are asked to enter their personal details into a fake login form which will harvest their credentials
Ransomwaretype of malware which encrypts files and demands payment from a user before they can decrypt and access their data
Shoulder surfinga form of cyberattack where a person or device watches people as they enter their passwords in order to harvest their credentials
Social engineeringa form of cyber attack (including phishing and shoulder surfing) where people are tricked into giving away their credentials
Unpatched softwareapplication or operating system software where a vulnerability has been identified that hasn't yet been fixed and could be exploited by hackers
USB deviceshacking devices made to look like mice or keyboards which may install keyloggers, viruses or other malicious software
5.2.4: understand methods of identifying vulnerabilities including penetration testing, ethical hacking, commercial analysis tools and review of network and user policies
Communication and the Internet
KeywordDefinition
Ethical hackinggetting permission to carry out penetration testing on a network or computer system and then reporting any vulnerabilities found so that they can be fixed
Exploittaking advantage of a vulnerability in a computer system or network to gain unauthorised access
Network policiesset of rules that determine how data is encrypted, stored and secured (e.g. backup frequency and blocking USB devices)
Penetration testingidentifying vulnerabilities in a computer system or network by attempting to hack in to it, testing for known exploits or weak passwords
Unauthorised accessViewing or changing data on a computer system or network when you don't have permission to do so
User policiesa set of rules that determine what happens when new people need access to a computer system or when they no longer need access (e.g. if they leave or get fired)
Vulnerabilitya weakness in a computer system or network that could be exploited to gain unauthorised access
Vulnerability scannersautomated software which can test a computer system or network for common security weaknesses
5.2.5: understand how to protect software systems from cyber attacks, including considerations at the design stage, audit trails, securing operating systems, code reviews to remove code vulnerabilities in programming languages and bad programming practices, modular testing and effective network security provision
Communication and the Internet
KeywordDefinition
Acceptable Use Policyset of rules that users have to sign which state what they are and are not allowed to do with a computer system or network
Access controlsomething developers should consider at the design stage: granting or denying certain functionality to different groups of users
Audit traila way of tracking down who is responsible for a cyber attack by keeping and checking records of all forms of access to a computer system or network
Authenticationsomething developers should consider at the design stage: planning how to prove that the person using the software is who they say they are
Bad programming practicewhen a software developer forgets or isn't skilled enough to write secure code (e.g. not validating data submitted by a client before trusting it on a server)
Code reviewsomething that should happen regularly whilst developers are creating software in order to check that no security vulnerabilities make their way into code that is released to the user
Code vulnerabilitiesmistakes in code which could be exploited by a malicious user in order to provide unauthorised access to a computer system or data
Design stagepart of the development process when programmers should consider how to make software secure before writing any code (e.g. what authentication or access control is required?)
Encryptionsomething that developers should consider at the design stage: whether sensitive data shouldn't be stored in plaintext
Modular testingsomething that software developers should do when they complete each part of a program in order to test that it works as expected without any security vulnerabilities
Network administratorsomeone employed to maintain hardware and make sure software is updated and patched regulalry
Operating systemthe software installed on a computer that may need regular updates in order to keep it secure as new vulnerabilities are discovered
Warningssomething developers should consider at the design stage: e.g. whether users should be prompted for confirmation before data is deleted
5.3.1: understand what is meant by the internet and how the internet is structured (IP addressing, routers)
Communication and the Internet
KeywordDefinition
Internet Service Providera company which provides network access to the Internet to a company or individual (for a fee)
IP addressa series of bytes which can be used to identify a computer or group of computers on a network
IPv4a commonly used type of IP address which only uses 4 bytes (32 bits) to store the address, meaning only 4 billion address are available
IPv6a type of IP address which uses 16 bytes (128 bits) to store addresses so that there are plenty available for all the people and devices connected to the Internet
Local Area Networka network made up of multiple devices connected together over a limited geographical area
Packet switchingthe process of splitting data into small chunks which are then transmitted between two computers over the Internet by finding the most efficient route for data through all the possible connections between them.
Routerdevice with multiple network connections which forwards network traffic to the correct destination
The Internetthe largest WAN in the world: an interconnected network of networks
Wide Area Networka network made up of multiple LANs over a large geographical area
World Wide Weba service that provides access to a huge quantity of information, made possible by protocols like HTTP and HTTPS over the Internet
5.3.2: understand what is meant by the world wide web (WWW) and components of the WWW (web server URLs, ISP, HTTP, HTTPS, HTML)
Communication and the Internet
KeywordDefinition
BrowserApplication software that a user uses to access the WWW
Domain namethe name of a web server or computer that can be used instead of an IP address
Domain Name Servicethe process of using a domain name to look up the IP address of a computer connected to the Internet
Hyper Text Markup Languagethe way of describing the content and structure of web pages in the world wide web
Hyper Text Transfer Protocolthe set of rules used to request and transmit data across the WWW
Protocol identifierThe first part of a URL which describes whether the resource should be requested using http, https or ftp
Uniform Resource Locatora unique name for a page or file that can be accessed over the WWW
Web pagean online resource that can contain text, graphics, video and sound and can be accessed via the WWW
World Wide Webservice which runs on the Internet to provide access to web pages, files and other data