AQA GCSE Computer Science Fundamentals of Computer Networks PDF

Head to www.savemyexams.com for more awesome resources AQA GCSE Computer Science Your notes Fundamentals of Computer Networks Contents Types of Network Wired & Wireless Networks LAN Topologies Network Protocols...

Head to www.savemyexams.com for more awesome resources AQA GCSE Computer Science Your notes Fundamentals of Computer Networks Contents Types of Network Wired & Wireless Networks LAN Topologies Network Protocols Network Security The Concept of Layers Page 1 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Types of Network Your notes Networks What are the different types of networks? A network is two of more devices connected together with the purpose of sharing resources There are three main types of network Local Area Network (LAN) Wide Area Network (WAN) Personal Area Network (PAN) For the exam it is important to know the advantage and disadvantages of each type of network as well as the advantages and disadvantages of networks as a whole What are the advantages of having a network? Users can share resources such as printers and connection to the internet Users can access their files from any computer on the network Communication can be made easier via email and social networks Users can share files and folders easily such as central databases and spreadsheets Servers can be used to provide centralised backups, updates and security What are the disadvantages of having a network? There is an increased security risk to data Malicious software can infiltrate the network and render it unusable Servers and switches can provide a central point of failure, resulting in users not being able to complete tasks using their computer Factors can impact the performance of the network such as the number of users and data on the network at one time Types of Network What is a LAN? A local area network (LAN) is a network which has a small geographical area (under 1 mile) Page 2 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources All of the hardware is owned by the company/organisation/household using it LANs will use unshielded twisted pair (UTP) cable, fibre optic cable or wireless connections (Wi-Fi) Your notes What is a WAN? A wide area network (WAN) is a network which has a large geographical area (over 1 mile) They are a collection of LANs joined together The computers on a WAN are connected via routers The hardware used to connect the networks together is not all owned by the company/organisation/household using it. Telephone lines owned by telecommunication companies are an example Page 3 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources WANs will use fibre optic cable, telephone lines and satellite to connect the LANs together Your notes What is a PAN? A personal area network (PAN) is a network that is used for transmission of data between devices in close proximity A PAN has a very short range (10 metres) Bluetooth is the most widely used PAN Typical examples of devices which make use of a PAN are: Wireless headphones Mobile phones Page 4 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Tablet Laptop etc. Your notes Worked Example (a) State one wireless method used to connect devices on a Personal Area Network (PAN) (b) A travel agent has offices in two sites that are 10 miles apart. Describe two differences between a Local Area Network (LAN) and a Wide Area Network (WAN) Answers (a) Bluetooth (b) Max two marks from LANs cover relatively small geographical areas // WANs usually cover a wide geographic area LANs often owned and controlled/managed by a single person/organisation // WANs often under collective/distributed ownership WANs are (usually) several LANs connected together WANs (usually) have a much larger number of devices/users than LANs LAN has a lower latency // WAN has higher latency WANs are (usually) slower than LANs The cost-per-byte for transmission is much higher on a WAN LANs and WANs use different protocols Page 5 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Wired & Wireless Networks Your notes To connect devices to a network, there are two main options: Wired Wireless There are advantages and disadvantages to each option which are explored below Wired & Wireless Networks What is a wired network? A wired network is a network where physical cables are used to join devices together and transmit data Computers can be connected to networks using many different types of wires to transmit data The most common types of cables in a wired network are: Ethernet Fibre optic Copper What is Ethernet? Page 6 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Ethernet is a wired networking standard to carry electrical signals between devices on a local area network (LAN) Your notes Ethernet is common in most offices and homes to connect devices such a desktop computers & servers Ethernet uses twisted pair cables to allow duplex communication What is fibre optic? Fibre optic is a type of cable that uses light to transmit data on a wide area network (WAN) Fibre transmits data at a much higher speed and has a much higher bandwidth compared to copper cables Fibre optic cable does not suffer from interference which makes them the most secure option to send sensitive data Fibre optic cables can cover a long distance without any degradation, they can span cities and countries What is copper cable? Page 7 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Copper is a type of cable originally used in telecommunication to transmit voice signals, forming the traditional landline phone network The ability to use copper to deliver network traffic on a wide area network (WAN) made the internet possible Copper cables degrade over time which limits their range compared to fibre optic Copper cable suffers from interference which can disrupt data quality Copper transmits data at a much slower rate, and has a much lower bandwidth compared to fibre optic Advantages & disadvantages of wired networks Advantages Disadvantages Speed - Fast data transfer Portability - Can't move easily, location is limited by physical cable Security - Better physical security Cost - Need more cables to add a new device Range - High (up to 100m), less susceptible Safety - Cables can be trip hazards, need routing along to interference walls, under floors What is a wireless network? Page 8 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources A wireless network is a network where connections are made using radio waves to transmit data through the air Your notes The most common types of wireless connections are: Wi-Fi Bluetooth What is Wi-Fi? Wireless fidelity (Wi-Fi) is a common standard for wireless networks Wi-Fi is common in most homes and offices to connect devices such as laptops, tablets & smart phones Using Wi-Fi, devices communicate with a wireless access point (WAP), which can be a standalone device or built into a router or switch What is Bluetooth? Page 9 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Bluetooth is another common standard for wireless networks Bluetooth is common in most homes and offices to connect devices such as headphones, controllers, Your notes keyboards & mice Bluetooth is used typically for a direct connection between two devices Advantages and disadvantages of wireless networks Advantages Disadvantages Portability - Easy to move around, location is only Speed - Slower data transfer than wired limited by range Cost - Less expensive to setup and add new Security - Less secure than wired devices Compatibility - Most devices are manufactured Range - Relies on signal strength to the WAP, signals with a built in wireless adapter can be obstructed (up to 90m) Worked Example Give three advantages of using a wireless network instead of a wired network Answer flexibility to expand network/add users/add own devices to the network there is no need to drill holes/install cabling mobility of user/devices (portable) modern devices are more likely to (be designed to) connect wirelessly (built in adapters) guest access (can add temporary connection) no trip hazards Guidance Cost can be accepted but only If a valid explanation is given Page 10 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources LAN Topologies Your notes LAN Topologies What is a network topology? A network topology is the physical structure of the network It defines how the network hardware will be arranged to create the network Two popular topologies to understand for the exam are: Star Topology Bus Topology Star Network Topology What is a star topology? A star topology has a central switch which all other devices connect to A switch is an intelligent device which ensures that traffic only goes to the intended device A star topology is commonly seen in most homes, businesses, organisations and schools What are the advantages of a star topology? If any single cable stops working, the rest of the network will continue to work An example you may have experienced would be in school when one computer won't log on to the network, but all other classmates can get logged on This is important because in other topologies if a cable was broken, all computers on the network would stop working which would have a negative impact on learning in schools and businesses completing their daily tasks What are the disadvantages of a star topology? The central switch is a single point of failure This means that if the switch stops working, all of the devices connected to it will not be able to connect to the network or any of its facilities and resources Page 11 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Bus Network Topology What is a bus topology? A bus topology is all devices connected by one single ‘bus’ cable, terminated at each end The terminators stop the signal bouncing back and causing errors A bus topology works by each device: ‘Listening’ to electrical signals Checking data packets for their specific address Ignoring data packets it does not recognise A bus topology has been replaced by much more efficient network topologies such as the star topology What are the advantages of a bus topology? Easy and cheap to set up as only one cable is required Does not rely on any other network hardware such as a central server/switch Page 12 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources What are the disadvantages of a bus topology? Low security as data is seen by all devices on the network Your notes Slow data transfer and prone to data collisions If the cable breaks, the whole network is affected (central point of failure) Page 13 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Network Protocols Your notes Network Protocols What is a protocol? A protocol is a set of rules that govern communication on a network There are protocols for different purposes, such as: Ethernet & Wi-Fi TCP/IP & UDP HTTP & HTTPS FTP IMAP & SMTP Ethernet & Wi-Fi What is Ethernet Ethernet is a family of related protocols used in data communication/transfer on a wired local area network (LAN) What is Wi-Fi? Wi-Fi is a family of related protocols used in data communication/transfer on a wireless local area network (LAN) Wi-Fi is a trademark, the generic term used to describe networks that make use of Wi-Fi is wireless local area network (WLAN) Page 14 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Examiner Tips and Tricks Key point to remember, Wi-Fi is a brand name! Any local area network that uses wireless technology to connect devices is known as a wireless local area network (WLAN) TCP/IP & UDP What is TCP/IP? TCP/IP is two protocols, transmission control protocol (TCP) and internet protocol (IP) that combined allow communication over the internet (WAN) TCP is responsible for making sure communication between two routers is error free IP is responsible for making sure data is delivered to the right device on a wide area network (WAN) What is UDP? User Datagram Protocol (UDP) is an alternative to TCP to send data across a wide area network (WAN) UDP is faster than TCP but less secure and does not guarantee error free transmission Page 15 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources UDP is an open, two way communication used in activities where some data loss is acceptable, for example online gaming Your notes TCP is much more reliable than UDP HTTP & HTTPS What is HTTP & HTTPS? Hypertext Transfer Protocol (HTTP) allows communication between clients and servers for website viewing HTTP allows clients to receive data from the sever (fetching a webpage) and send data to the server (submitting a form, uploading a file) HTTPS works in the same way as HTTP but with an added layer of security. All data sent and received using HTTPS is encrypted HTTPS is used to protect sensitive information such as passwords, financial information and personal data FTP What is FTP? File Transfer Protocol (FTP) allows sending and receiving files between computers Uploading and downloading files to/from a web server is often completed using FTP Page 16 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources FTP offers greater efficiency and support for bulk transfers and large files such as resuming interrupted transfers Your notes FTP clients are software applications that use the FTP protocol to make the process easier for users IMAP & SMTP A family of protocols that handle sending and receiving of email across the internet (WAN) What is SMTP? Simple Mail Transfer Protocol (SMTP) is a protocol that allows communication between an email sender and the email server, and between different email servers using the internet In the diagram above, SMTP is used to transfer the senders email to their email providers server and SMTP is used to transfer the email to the recipients email server Page 17 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources What is IMAP? Internet Message Access Protocol (IMAP) is a protocol for downloading emails to a device from an Your notes email server Once the email has been retrieved, a copy is retained on the mail server Worked Example Explain the purpose of the HTTPS protocol Answer sending/receiving web pages using an encrypted connection // provides an encrypted version of HTTP more secure web transactions authentication of the website being visited encryption of the data between the server and the client reduces likelihood of man-in-the-middle attacks Page 18 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Network Security Your notes The Need for Network Security Why do we need to protect a network? As technology continues to advance at a rapid rate, sensitive data is increasingly stored on networks making it a target for hackers Computer networks face a variety of threats and they can cause a large number of issues for a network The main methods of securing networks are: Authentication Encryption Firewalls MAC address filtering Authentication What is authentication? Authentication is the process of using credentials to check if a user is who they say they are Credentials are typically: Usernames & passwords ID badges Access/security codes Biometrics (finger prints, retina, voice etc.) Credentials are verified to see if they match what is stored by the system When can authentication be used? Authentication is used in computer systems when data or services require approved access, and should not be available to everyone Examples include: Logging into networked computers (i.e. school, office etc.) Page 19 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Your notes Accessing online services (i.e. banking, social media, entertainment streaming platforms etc.) Page 20 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Encryption Your notes What is encryption? Encryption is a method of converting plain text into ciphered text to be stored Encryption uses complex mathematical algorithms to scramble the text Asymmetric encryption, also known as private key, public key encryption is often used for web pages and other communication When can encryption be used? Encryption should be used in any situation where sensitive data is being transmitted across a network Examples include: Passwords Bank details Personal information Firewalls What is a firewall? A firewall is a barrier between a network and the internet A firewall prevents unwanted traffic from entering a network by filtering requests to ensure they are legitimate It can be both hardware and software and they are often used together to provide stronger security to a network When can a firewall be used? Hardware firewalls can be used to protect a whole network and prevent unauthorised traffic, they usually come built in to a router Software firewalls can be used to protect an individual device on the network, monitoring the data going to and from each computer, they are usually installed as part of the operating system MAC Address Filtering What is MAC address filtering? Page 21 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources MAC address filtering is the process of using a devices MAC address to determine if a device can or cannot connect to a network Your notes Devices with MAC address that are allowed to connect are placed on a ‘white list’, and those not allowed on a ‘black list’ If a device tries to connect to a network and the MAC address is not on the list, connection is refused A MAC address is a unique identifier embedded into a device during manufacturing MAC addresses are given to any device capable of connecting to a network, wired or wirelessly When can MAC address filtering be used? MAC address filtering is predominantly used on wi-fi networks to limit access to the network to only devices on the ‘white list’ Only approved physical devices can connect to the network Worked Example Describe one security measure that could be used, in addition to a password, to make sure that a user is who they are claiming to be Answer 1 mark for method, 1 mark for valid expansion A code can be sent to your phone as a (text) message/in an email/as a pop-up to one of your devices... the user then types in the code (as well as the password) any hacker would need to access the phone as well as the password An authenticator app on a mobile phone... this generates a code which the user uses to complete the log-in Use two-factor authentication/2FA // strong customer/multi-factor authentication... this asks for a second form of identification such as something you know/possess/are Biometrics... (to be authenticated) reference data is compared to the individual’s (unique) biometric data Smart cards/fobs.... the user inserts a Smart Card to a reader and enters the PIN, the authentication request is then verified (using digital certificates) Page 22 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Ask security / memorable question... the user is asked a question that only they know the answer to Your notes Page 23 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources The Concept of Layers Your notes The Concept of Layers Networks rely on many complex parts all working together at the same time, from different types of network, the different operating models, the internet, wired and wireless to encryption, addressing and protocols Managing the complexity of networks is helped with the use of layers What is a layer? A layer is a sub part of a more complex task Dividing network tasks into layers reduces the complexity and makes each layer more manageable An example of layers can be seen in the TCP/IP protocol which uses a 4-layer model known as a 'stack' What are the advantages of layers? Layers are self-contained which makes managing, repairing and upgrading easier as each layer can be worked on independent of other layers Layers allow for focus on specific parts of a protocol without affecting other layers Promotes data exchange (interoperability) between hardware and software Examiner Tips and Tricks In the exam you are required to understand the concept of layers AND describe the main function of TCP/IP layers TCP/IP Model What is the TCP/IP model? The TCP/IP model is made up of two protocols (TCP & IP), containing 4 layers, that work together to package, address, transmit and receive data on a wide area network (Internet) There are four layers that make up the TCP/IP protocol stack: Application Transport Page 24 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Internet Link Your notes Different protocols operate on different layers Layer Function Protocols Application Application software such as web browsers and email clients HTTP, HTTPS, FTP, operate here SMTP, IMAP Transport Enables communication between two hosts to agree settings TCP, UDP such as size of packets Internet Addresses and packages data for transmission. Routes the IP packets across the network Link Physical network hardware such as NIC is located, OS device drivers also sit here Page 25 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers  Head to www.savemyexams.com for more awesome resources Examiner Tips and Tricks The link layer can sometimes be referred to as the ‘network access layer’ or ‘network interface layer’, Your notes you are not expected to remember the alternative names in this exam! Worked Example TCP/IP is a set of protocols based on layers. 1. With regards to network protocols, define what is meant by a ‘layer’ 2. Describe one advantage of using layers to construct network protocols Answers Breaking up a complex task into more manageable sub tasks Self-contained …it allows different developers to concentrate on one aspect of the network A layer can be taken out and edited without affecting other layers… …it promotes interoperability between vendors and systems Page 26 of 26 © 2015-2024 Save My Exams, Ltd. · Revision Notes, Topic Questions, Past Papers