IT SAGS Notes 2022 PDF

INFORMATION TECHNOLOGY (IEB) EXAM PREP. THEORY NOTES This document is set up in terms of Appendix G of the IEB’s SAGS document for IT as of 2022; I do not claim any definitions or explanations as work of my own and don’t claim this intellectual property to be mine. This is merely a compilation of va...

INFORMATION TECHNOLOGY (IEB) EXAM PREP. THEORY NOTES This document is set up in terms of Appendix G of the IEB’s SAGS document for IT as of 2022; I do not claim any definitions or explanations as work of my own and don’t claim this intellectual property to be mine. This is merely a compilation of various sources’ definitions and explanations to assist one in their preparation. No profit should be drawn from this document. System Technologies Hardware and Software Hardware is the physical components of a computer that runs and stores the software on the computer, e.g. CPU, RAM Software is a set of computer programs and associated documentation and data or a set of instructions that tell a computer what to do, e.g. Microsoft Word ICT System ○ Information and Communication Technology ○ A term used to describe systems that incorporate electronic technologies and techniques to manage, capture, transmit and display information and knowledge Computers are devices, usually electronic, that processes data according to a set of instructions Input Processing Output (IPO) Model ○ represents a system in three stages: input, process and output ○ Input is achieved by giving the system data to process ○ Processing occurs when the computer interprets and executes the information given as an input ○ Outputs are the result produced by the system after processing Advantages and disadvantages of using computers 1  Advantages Disadvantages Speed - Computers can make High cost - computers are expensive calculations and logical comparisons way faster than any human being Accuracy - computers can’t make Takes over human jobs - computers mistakes if the code is functioning and take jobs that no longer need to be the data inputted is correct performed by humans Repetitiveness - computers can do the The waste produced by computers - same, tedious job for a long period of new computers are constantly time while humans may become produced which leads to older ones mentally fatigued being thrown away and Versatility - a computer can perform Health problems - computers have a many functions with the help of certain negative impact on your eyes, neck and software back Data ○ Collection of facts ○ Raw and unorganised ○ It’s meaningless on its own Information ○ Facts that are put into context ○ Organised and analysed ○ It’s meaningful seeing that it is data that has been interpreted and analysed System types ○ Laptops = portable personal computers (PC) ○ Desktops = PCs designed for regular use at a single location on or near a desk due to its size and power requirements ○ Server = a computer or computer program which manages access to a centralised resource or service in a network 2  ○ Embedded computers = hardware and software that is designed to perform a highly specific function, e.g. a camera of a washing machine's embedded computers will not be the same since they perform very different functions ○ Smart wear = wearable technology that monitors the wearer’s physical activity and condition. Smart wear usually use bluetooth to connect to a smartphone ○ Tablets = portable, touchscreen devices with a rechargeable battery; usually smaller than a laptop but larger than a smartphone ○ Smartphones = portable computer devices that combine mobile telephone and computing functions into one unit ○ Single board computer (SBC) = a complete, functioning computer in which the microprocessor, input/output functions, memory, and other features are all built on a single circuit board, with no expansion slots for peripherals, e.g. Raspberry Pi and Arduino Mobility/Portability ○ Most portable in descending order: smart wear, smartphones, tablets, laptops, desktops, servers Processing Power ○ Processing power highest to lowest: server, supercomputer, desktop, mobile Operating Systems ○ The main control program in a user’s device ○ Creates a user interface ○ Load and run programs ○ Manage resources ○ Acts as an interface between hardware and application programs ○ e.g. Desktop: Windows, Linux, macOS ○ e.g. Mobile: Android, iOS, Windows Phone ○ e.g. Embedded OS: OSs found in ATMs, electric vehicles, cameras Application software ○ Stand-alone applications = software that don’t require other applications in order to work, e.g. Notepad, MS Word ○ Network applications = applications that run on one host, providing communication to other applications on a different host, e.g. a web browser 3  Main Hardware components of typical computing devices ○ CPU; made up of the CU, ALU and registers ○ Primary Storage like RAM, BIOS and ROM ○ Secondary Storage like Mechanical Hard Disk Drives (HDDs), Solid State Drives (SSDs), SD Cards and flash drives ○ Input devices like pointing devices (mouse), keyboards, scanners, microphones, biometric devices ○ Output devices like monitors, printers, speakers ○ Ports like USB and HDMI ○ Most of the above mentioned devices connect to the motherboard CPU Design ○ Registers Stores current instructions and its data Current instructions are broken into segments and individually stored Are made from extremely fast and expensive SRAM (Static RAM); SRAM have no capacitors and are thus constantly refreshed which leads to a higher access time (faster access) 32- bit computers have to process 64-bit numbers in 2 stages, therefore a 64-bit computer has better performance. Note that a 64-bit computer isn’t necessarily twice as fast as a 32-bit; some 64-bit code has higher memory consumption that lowers the performance ○ Control Unit (CU) Controls the execution of each instruction Sends read & write signals to the memory Data fetched from memory is stored in either the CU or ALU ○ Arithmetic Logic Unit (ALU) Calculations & logical comparisons take place here The accumulator is the register that results of each execution Data is loaded from the RAM to accumulator and saved from accumulator to RAM 4  ○ Serial Processing Outdated; CPUs only process instructions one at a time Single core processors that break a problem into a set of instructions and execute it sequentially ○ Parallel processing Simultaneous execution of instructions that are part of a problem Simultaneous processing is achieved by running the instructions on multiple microprocessors Hyperthreading (must be supported by the OS) Developed by Intel in 2002 Thread = part of a program; a set of instructions Process = regards entire program A hyperthreaded CPU appears like 2 logical CPUs in the OS, while in actual fact there is only one with 2 sets of registers to enable simultaneous execution The next instruction is preloaded into the registers whilst the first instruction is being processed Multiprocessing (must be supported by the motherboard and OS) Multiple cores on a CPU chip Entire core is duplicated instead of only the registers ○ Processor Cache - Cache stores data so that requests for data can be served faster A processor has a much faster speed that RAM Caching is done to prevent the CPU from being idle (doing nothing) A small amount of fast memory is allocated close to the CPU which stores the next few instructions Cache consists of fast SRAM chips Level 1 cache = smallest, fastest (speed of CPU) and closest to CPU Level 2 cache = larger than L1, slower than L1 (half the speed of CPU) Level 3 cache = largest and slowest, still closer to the CPU than the RAM 5  Cache hit = data that is requested was found in the cache Cache miss = data that is requested was not found in the cache RAM (Random Access Memory) ○ Most common: Double Data Rate Synchronous Dynamic RAM (DDR SDRAM) ○ Double Data Rate refers to the fact that data is transferred faster than the original rate of once every slock pulse; data is now transferred at the rise and fall of every pulse (think of a sine graph). DDR3 is widely used ○ Synchronous refers to the fact that the refreshing of RAM chips is in sync with the CPU ○ Dynamic RAM (DRAM): each chip has a capacitor that loses charge and needs to be refreshed multiple times per second ○ Latency is the time taken for a program to respond Motherboard The central printed board that connects components and devices in a computer to one another ○ Buses connect components and devices ○ Slots connect devices like graphic cards and hard drives ○ Ports (e.g. USB & audio) connect external devices to the computer ○ System Clock A microchip that regulates timing, speed and synchronisation of all computer functions It works by having a crystal in the chip that vibrates at a specific frequency when electricity is applied Speed of a computer is measured in clock speed, e.g. 1 MHz = 1 million cycles per second Overclocking: Making computer run faster than it was designed by manipulating frequencies at which the components are set to run Overclocking per component = the CPU operates faster than the system clock by changing its own multiplication factor 6  Overclocking the whole system = system clock speed is increased, affecting all components that detect the system clock The danger is that overclocking leads to more power consumption and thus more heat generation which causes a fire hazard Cooling by fans, liquid cooling and heat sinks can be used to lower the heat that is caused by overclocking ○ Speed vs Throughput The CPU speed is usually measured in GHz while the RAM is in MHz The maximum/ theoretical speed is called the speed or bandwidth (networking) The actual speed due to latency is called the throughput ○ Internal Bus/Front Side Bus Mainly connects the CPU & RAM Consists of the Data bus, Address Bus & Control Bus Wider bus = Ability to carry more data Data Bus Transfers the instruction between the CPU & RAM Wider bus means a greater throughput Address Bus Transfers the physical address of the instruction The width of the bus determines how much memory can be addressed by the system 64-bit address buses have the ability to address more memory. It doesn’t create more memory; more memory requires you to buy more RAM Control Bus Carries commands between the CPU & RAM For example, is the data being read or written? ○ External buses PCI Express (Peripheral Component Interconnect Express) Slots are used to connect graphics, RAID and Wi-Fi cards as well as SSDs 7  SATA (Serial Advanced Technology Attachment) Connects mass storage like hard drives USB (Universal Serial Bus) Standardises connections for almost any peripheral to computers for communication and/or power supply NVMe (Non-Volatile Memory Express) Connects SSDs to the motherboard Allows better read/write speeds that SATA M.2 Format Designed to operate at high speeds while consuming little space and power e.g. Wi-Fi and Bluetooth cards or SSDs Can use any of these buses: SATA 3.0, PCIe 3.0, USB 3.0, NVMe 3.0 Secondary Storage ○ Size vs Speed vs Cost Cost (Descending) Size Speed External HDD 1-8 TB 3-6 Gbps HDD (PC) 1-8 TB 6 Gbps HDD (Laptop) 0,5-4 TB 3-6 Gbps SSD 120-960 GB 500-1000 Mbps Flash Memory Up to 1 TB Up to 10 Gbps ○ Cloud Storage Computer is connected to remote storage via the internet Limited free storage; optional storage space expansion for a fee Speed is determined by the internet connection Cost applies not only for storage but also for the bandwidth to connect to it 8  Other Caching ○ Any device that uses a faster medium to store data temporarily is caching ○ Disk Cache Hardware mechanism that improves the read/write time to a hard disk Usually part of the hard disk but can also reside in RAM A few lines are loaded into the cache instead of reading line by line ○ Browser Cache Copy of a website stored on your hard disk Web pages will load faster in the future, although they might not be up to date ○ Web/Proxy Cache Stores recently accessed web pages on a server in a network Access time to website will be faster if it is again loaded in the future Browser cache = per user; Proxy cache = anyone on the network Computer Performance and Reliability ○ Modular Design = parts of a device can be bought separately and put together Smaller devices like smartphones are less modular Advantages: Repairs. Only a component that needs fixing has to be fixed, not the whole device Upgrades. Hardware can be upgraded without replacing the entire system Flexibility. A variety of components can be added to the device ○ Improving processor speed Hyperthreading = duplication of registers on a single processor chip Multiprocessing = multiple CPUs (cores) on a single chip Processor cache = small amount of memory on or near the processor that predicts the next instructions in order to increase performance Register size = 64-bit registers allow for a better performance in comparison to 32-bit register Bus size = wider buses allow for more memory to be allocated 9  Clock manipulation = overclocking can be done per component or for the entire system ○ Expansion cards Plugged into a slot on the motherboard Usually provides better functionality that onboard counterparts ○ Onboard Hardware component embedded into the circuit board Can’t be removed but can be disabled via CMOS Contradicts modularity e.g. GPU, sound card ○ Co-processors = assistant to the CPU that takes over some of the workload Graphics Translation from bits to images/colour Images are rendered with a higher resolution if a Graphics Processing Unit (GPU) is used Applications using the GPU will run faster which increases the overall performance of the system Graphics Cards and Video Cards are other names for the GPU Video RAM can be used to improve graphics Integrated graphics GPU is embedded into CPU and normal RAM is used instead of VRAM Devices that use high graphics switch to integrated graphics to save power Maths Assists the ALU with complex calculations Calculations with large floating point numbers (many decimal places) can place a burden on the CPU Calculations are performed faster Nowadays most computers have maths co-processors built in ○ RAM = volatile memory that stores loaded programs and data Frequency = affects max bandwidth; determines how much data can be travel to & from RAM 10  Latency = how quickly RAM responds to a request The optimal speed is achieved when frequency is high and latency low Virtual Memory = opposite of cache; when more RAM is needed by the system, a section of the slower secondary storage is used. Data stored there is known as a paging file ○ Buses Internal Bus/ Front Side Bus Control Bus, Address bus, Data Bus External buses Connects external devices to the computer for storage, printing, monitors etc. Slower than the internal bus e.g. PCIe, NVMe, USB, SATA ○ Ports USB USB Standards = speed & function of USB e.g. 3.1 or 2.0 USB Ports = shape of port e.g. Type-A or Type-C Type-A = familiar rectangular port, usually on the host device Type-B = square shape for printers and external hard drives USB 3.0 Micro B = used prior to the introduction of Type-C Type-C = doesn’t have a distinct top and bottom side; used for charging and data transmission on newer cell phones and laptops USB On-The-Go = allows mobile devices to acts as hosts (Android) HDMI (High Definition Multimedia Interface) Developed in 2003 in search for higher quality images Standard for PC monitors and HD televisions Carries high definition video and audio signals DisplayPort 11  Developed in 2006 to upgrade VGA and DVI (which didn’t have HD) Intended more for laptops/desktop monitors Carries HD video and audio signals Has a higher bandwidth that HDMI Daisy Chaining = instead of using multiple cables to create a multi display setup, monitors can be linked via DisplayPort cables (must be supported by monitors) Thunderbolt Widely used by Apple for display or storage devices Thunderbolt 3 is faster and has a better display than USB Type-C Thunderbolt 3 is compatible with USB Type-C, but not vice versa Thunderbolt 3 supports daisy chaining, USB Type-C doesn’t ○ Secondary Storage: HDD vs SSD HDDs are spinning disks while SSDs have no moving mechanical parts. This means: SSDs run silently SSDs are more resistant to shock SSDs are safe from the effects of magnetism SSDs consume less power SSDs have faster access time compared to HDDs (lower latency) SSDs boot up faster than HDDs SSDs are although more expensive than HDDs ○ Types of SSDs M.2 Format Small form factor; no cables; beneficial for small devices M.2 SSDs connect directly to M.2 socket on the motherboard Uses PCIe bus (for NVMe SSDs) or the SATA bus PCIe NVMe M.2 SSDs NVMe that connects via PCI-Express Runs faster since it doesn’t access the SATA bus 12  By installing your OS and frequently used programs on the NVMe, you will utilise it SATA SSDs Older and slower technology; requires power and data cables M.2 vs SATA SATA has 2 form factors: 2,5 inch & M.2 2.5 inch requires cables; M.2 plugs directly into the motherboard ○ Typical Computer Systems Laptop/Desktop Entry-level: Adequately performs web-surfing, email and word processing. For small businesses or use at home, that don’t require high graphics Mid-level: Better in terms of graphics and processing when compared to entry-level High-level: For power users, e.g. video editors, gamers, graphic designers, audio producers Server Computer Powerful computer, provides services to other computers in a network, like data sharing Requires: high processing speed, high amount of cache, high secondary storage capacity, high amount of RAM Types of Servers: File, Mail, Print, Web, Antivirus, Application Run by domain/network administrator(s) Mobile Technologies Wearable Tech ○ Technology worn on or near the skin ○ Detect, analyse and transmit info about the user, like vital signs ○ Part of the Internet of Things (IoT) ○ Smart watches: tracks health and fitness and sends notifications, connects through Bluetooth 13  ○ Smart clothing: circuits interwoven into textiles of clothes, uses sensors and haptics to collect data ○ HMD: Head Mounted Displays. Device worn on head with display for one or both eyes Virtual Reality (VR) = complete immersion into a virtual environment (e.g. Oculus Rift) Augmented Reality (AR) = digital content overlayed over the true world (e.g. Google Glass) ○ Implantable Devices: devices surgically implanted for health records or identification data Constraints of Mobile Tech ○ Screen size = less content is displayed on mobile screens, smartphones require more interaction to obtain the same amount of info as you would on a laptop ○ Single window = only one window is displayed on most mobile devices along with keyboards that take up screen space. Apps therefore need to be self sufficient, everything has to happen within the app ○ Touch Screen = larger buttons and icons are required and keyboards tend to be small and crowded ○ Computing power = CPU chips uses lower voltages and can be turned off when not in use ○ Battery life = brightness of screen and usage of device affects battery life. Smaller devices have smaller batteries and tend to have less battery life, but less charging time ○ Power consumption = most intensive tasks: display, processing, maintaining connections, location services 14  Start Up and Boot Up Software ○ Boot Sequence Initial set of operations performed by computer when it’s turned on, performed by the boot loader Hardware devices are checked before the OS is loaded If all is fine, the OS is loaded from the main hard drive into RAM ○ Operating System Functions Provides a user interface Loads and runs programs Manages resources Offers an interface between hardware and application programs ○ BIOS (Basic Input-Output System) Low-level software that resides on a non-volatile ROM chip on the motherboard Software that permanently resides in ROM is called firmware BIOS is responsible for POST (Power-On Self Test) and loading the OS ○ Kernel The core of a computer’s OS that remains in the RAM It is responsible for the translation of I/O requests, from software, into instructions for the CPU ○ CMOS (Complementary Metal Oxide Semiconductor) Stores hardware and software settings Battery backed, non-volatile memory so that it settings are not lost when the computer is off ○ When a computer is switched on: POST checks hardware Inventory of hardware is obtained from the CMOS Hardware is tested to check functionality BIOS locates the Master Boot Record to load and execute the OS kernel 15  ○ UEFI (Unified Extended Firmware Interface) A modern substitute for BIOS Can boot drives up to 2,2 TB Can run in 32-bit or 64-bit User friendly: mouse support and graphics Secure boot: OS is checked for validity to ensure there is no malware Networking features: can aid in remote troubleshooting & configuration Processing Techniques ○ Hardware Hyperthreading = two threads appear to execute simultaneously due to there being two sets of registers on the CPU Multiprocessing = computer uses more than one CPU (core) for processing ○ Software Multitasking = the ability of the OS to make it appear that more than one task is being executed simultaneously, when in actual fact, the CPU rapidly switches between all running tasks Multithreading = more than one task in the same time executed simultaneously ○ Note! Thread = part of a program; a set of instructions Process = regards entire program Interrupts ○ CPU is suspended while waiting for input ○ Status changes from ‘suspended’ to ‘ready’ when an input is acquired ○ An interrupt is a signal sent to the CPU from hardware or software, indicating the need for the CPU’s attention; the CPU stops its current task for the interrupt 16  ○ Software interrupt = generated from a software program e.g. dividing by 0 or when I/O is required ○ Hardware interrupt = sent from a device e.g. a printer running out of paper ○ IRQ = Interrupt Request Number, used by CPU to identify device that sent an interrupt request ○ IO Range (buffer) Buffer = temporary storage in RAM to speed up a slow I/O device, e.g. loading an entire file first before reading it line by line Once a file is closed or saved to secondary storage, the buffer is flushed Virtual Memory ○ When RAM is full, the OS allocates a section of the hard disk and uses it as an extension of RAM for memory ○ This is kind of the opposite of caching, a slower device is used when the faster RAM is full ○ Using virtual memory slows the computer down because copying to a hard disk takes much longer than reading and writing RAM ○ paging copies a block of memory to or from disk ○ swapping copies an entire process to or from disk Machine Cycle ○ High-level languages must be translated into binary so that the CPU can execute it ○ FETCH ; retrieve the instruction from memory ○ DECODE ; translate retrieved instruction into computer commands ○ EXECUTE ; perform the computer commands ○ STORE ; send/write the results back in memory ○ Control Unit of CPU sends read/write signals to memory address of the stored data ○ Instruction is broken down (decoded) and stored in the registers temporarily 17  ○ Accumulator in the ALU stores the result of each execution; saved data is written from the accumulator to RAM Programming Tools ○ High-level Languages (closer to human language) High level of abstraction from underlying work Variables, arrays, objects e.g. Python, Java, Delphi ○ Low-level Languages Machine language/code or assembly language Assembly language is a low-level language translate into machine code by an assembler Machine language is the closest to what a computer can understand, e.g. binary, hex ○ Interpreters No compilation stage Code is read line by line, translated to machine code and executed Advantage: if there are syntax errors, the program will run up till the error; it is easy to find the error Disadvantage: the line-by-line interpretation has to happen every time the program is run; it is a long, slow process e.g. JavaScript and Python ○ Compilers Code is transformed into an executable form before running it Machine Code Generation (one stage) Source code translated directly to machine code by creating an ‘object code’ file Object code = machine dependant; a compiled program can only execute on a machine it was compiled for e.g. Delphi is compiled to a ‘.exe’ file, which is only runnable on Windows Intermediate Representation (two stage) 18  Stage 1: Code is compiled into an intermediate representation called bytecode. Bytecode can the be read without needing to re-read the source code Bytecode must be further interpreted to be read e.g. If Java source code is compiled into bytecode in a ‘.class’ file which can then be interpreted by a Java Virtual Machine A JVM mimics a Java processor, bytecode can thus execute, regardless of the OS Advantage: once it is compiled it can execute without needing to be recompiled Disadvantage: a syntax error would result in the code not running at all 19 Internet and Communication Technologies LANs Network = Consists of computing devices (nodes) connected using a communication medium/channel LAN ○ A group of connected nodes within close proximity of one another ○ Useful for sharing resources like files, printers and applications Ethernet is technology that connects devices in a LAN and enables them to communicate through a common protocol and physical wiring Network hardware/devices/nodes ○ Client Any computer hardware or software device that requests access to a service provided by a server Role of client in a network: Any computer which receives service (server and client could be the same machine) ○ Server A powerful computer that provides services to a network such as a file server or print server Role of a server in a network: A computer that provides service to clients e.g. authentication, file sharing and email ○ Switch = networking hardware that connects devices on a computer network by using packet switching to receive and forward data to its destination ○ Router Transfers data from a LAN to an external network, like the internet Connects different networks that use the same protocol Boosts signals and uses the nodes’ IP addresses to determine the best path for packets to travel 20  Routing table = info stored about networks connected to router; the router uses this table to determine the best route for data ○ NIC (Network Interface Card) = The physical interface or connection between the computer and the network cable ○ Bridge A bridge connects network segments, strengthens the signals as they pass through it It will only forward packages if they need to be forwarded (based on their MAC Address) Can be used to divide LANs into separate segments but can also connect separate LANs A bridge reduces network traffic ○ Repeater Connect network segments over long distances, since the signal weakens Unlike a bridge it doesn’t make intelligent decisions and forwards all packages ○ ADSL ADSL = Asymmetric Digital Subscriber Line a technology that facilitates fast data transmission at a high bandwidth on existing copper wire telephone lines to homes and businesses ADSL router provides functions and services like: Firewalls Can act as a switch Hotspot Connection to the internet Bounded Connection Media ○ Twisted-pair Cable 2 insulated strands of copper wire twisting around one another Twisting helps to prevent electrical interference ○ Unshielded Twisted-Pair UTP = most widely used network cable 21  Advantage: Relatively low cost Easy installation Disadvantages: Can’t span over long distances Copper cables’ inherent weaknesses: ○ Eavesdropping = signals can be intercepted ○ Attenuation = strength of signals lost over distances ○ Crosstalk = two cables close to each other interfere; more twists in cable means less crosstalk ○ Electromagnetic Interference = signals in cable can be corrupted by electromagnetic signals ○ Fibre-optic cables Data carried in the form of pulses of light Thin cylinder core of glass or plastic surrounded by cladding Glass strand carries signals in one way only, thus 2 strands are used per core Multimode fibre = larger core; used over shorter distances Single mode fibre used over longer distances Advantages: fast, secure data transmission, no electrical interference Disadvantages: more expensive than UTP, hard to install Unbounded Media - no physical connection ○ Wireless Oftenly used for long distance data transmission e.g. radio communication, microwave communication, visible & infrared light ○ Bluetooth Short wavelength radio transmission over short distances Signals sent from fixed and mobile devices creating Personal Area Networks. PANs are highly secure Wireless, inexpensive and automatic Can handle voice and data transmission simultaneously ○ Near Field Communication (NFC) 22  Wireless connection within very close proximity Commonly used for contactless payment (e.g. Apple Pay) ○ Radio Waves Electromagnetics waves used for communication technologies and data transfer Higher frequency of wave means it will travel shorter distances Types of networks ○ PAN (Personal Area Network) The PAN is used by an individual for communicating between devices such as a desktop computer, Laptop, smartphone, smart wear and tablet ○ LAN (Local Area Network) A network within a small area such as a building or room. ○ MAN (Metropolitan Area Network) A MAN is made up of LANs interconnected using high-speed connections across a city or metropolitan area ○ WAN (Wide Area Network) A WAN is made up of interconnected LANs and/or MANs in different cities or different countries ○ GAN (Global Area Network) A worldwide WAN such as the Internet is called a GAN Reasons for using a network ○ Communication ○ Access and sharing of resources ○ Centralisation ○ Data transfer ○ Productivity Advantages and disadvantages of a network Advantages of Network Disadvantages of Network - Centralisation of data - Lacks independence - Boosts storage capacity - Spread of viruses and malware - Accessibility of network - Cost of network 23  Network Topologies ○ The physical setup of a network; the way in which the network devices are connected ○ Star Switch connected to NIC of each nodes via UTP of fibre cables The switch is typically in a central position with the nodes around it Advantages: Easy to set up and maintain A problem with a single cable/node doesn’t upset the whole network Easy to extend Disadvantages: A lot of cables If the switch fails, the network fails ○ Bus Not used often nowadays All nodes connect to a single cable The central cable has a terminator at its ends so that the signals don’t bounce out Advantages: Less cables No switch = lower cost Easy to add nodes Disadvantages: Faults are difficult to trace since all the nodes share a common cable If the main (central) cable fails, the network fails The network can get congested; all signals share a cable ○ Tree Topology Also called a Star-Bus topology 24  Combination of star and bus network topologies ○ Ring Nodes connect to one another in a closed loop Signals travel around the loop, passing through each node Each node boosts the signals travelling through it Two rings are often used for the case in which one fails Advantages: Orderly Little signal degradation Easy to extend Disadvantages: Each node needs to work; if one fails, the network does too Changes in devices can upset the network Slow ○ Hybrid A combination of any of the above mentioned topologies Advantages: Error detection is easy Physical network layout can be adapted to suit the building layout Can be easily extended Disadvantages: Difficult to set up Expensive ○ Mesh A collection of wireless nodes with access points that are spread out in large numbers All nodes are connected to one another Nodes use common Wi-Fi standards to communicate Advantages: No cabling; inexpensive Robust 25  Easy to extend Disadvantages High workload for nodes Initial set up is complex Network Addressing ○ IP Address (IP = Internet Protocol) Numerical label assigned to nodes so that they communicate on the internet Static = device is manually configured and unlikely to change their IP address, e.g. servers and printers Dynamic = IP address changes over time like phones IPv4 = 32-bits address IPv6 = 128-bit hexadecimal address, thus larger address space ○ MAC Address (Media Access Control) Unchangeable hardware identification number A MAC address is required to be part of a LAN It is a 48-bit address with 6, 2-digit hexadecimal numbers ○ Internet Protocols How data is transmitted between computing devices and over networks ARP (Address Resolution Protocol) MAC address is linked to a computer’s IP address in an ARP table (stored in RAM of NIC) ARP table stores MAC addresses of all devices on the network in order to know which device sent data DHCP (Dynamic Host Configuration Protocol) Takes the manual work out of IP addressing DHCP server assigns IP addresses to devices from a pool of unused addresses If a device goes offline and returns online after a while, the IP address may change DNS (Domain Name Servers) Internet’s equivalent to a phonebook 26  Machines operate using IP addresses Maintains a directory of domain names and translates them to IP addresses Central Registry: where info about domain name servers is stored TCP/IP Defines the rules computers must follow when communicating over the internet of a network Browser and email applications use this protocol (HTTP, FTP) TCP (Transmission Control Protocol) No data corruption Connection oriented; a lost connection during the sending of data will result in a request for the lost data from the server If 2 messages are sent, they will be received in that order e.g. www, email, file transfer UDP (User Datagram Protocol) Subject to data corruption Connectionless; data won’t necessarily get to its destination If 2 messages are sent, there is no guarantee for them to be received in that order e.g. streaming applications, VoIP, multiplayer video games Broadcast vs Point-to-Point Communication ○ Point-to-point = connection between 2 individual nodes, e.g. telephone call ○ Broadcast = communication channel shared by all devices in the network; the signal from the sender is receiver by multiple receivers, e.g. radio station ○ I 27  OSI model (Open System Interconnection) ○ Model developed to establish compatibility for different protocols and technologies ○ It consists of 7 layers through which network transmissions pass ○ Each layer is responsible for a certain formatting of the data as it passes through it ○ When data is sent it is broken up as it passes down through the layers from layer 7 to layer 1 ○ When data reaches layer 1 of the sending machine it is sent through a medium to layer 1 of the receiving machine ○ When data is received it is reassembled as it travels upwards through the layers from layer 1 to layer 7 ○ Layers also communicate on a virtual level, e.g. layer 3 of the sending machine will have information about layer 3 of the receiving machine ○ Layers: Layer 7: Application An interface to enable the user to interact with an application or network e.g. reading messages, transferring files HTTP, FTP Layer 6: Presentation Translates/Formats the data for the application based layer on the syntax the application accepts Compression occurs here Encryption and decryption takes place here ASCII, PNG, MIDI Layer 5: Session Establishes, maintains and terminates connection between applications Authenticates and reconnects after an interruption X.225, ZIP Layer 4: Transport Performs logical addressing (IPv4 or IPv6) 28  Responsible for transferring data across a network Provides error-checking mechanisms and data flow controls Determines the rate, size and destination of the data to be sent Data is broken into segments and sent to designated ports; port number ensures that the segments reach the correct destination; sequence number ensures they arrive in order TCP (within TCP/IP) Layer 3: Network Moves data into and through networks Data segments travel through networks in the for of packets This layer assigns a destination IP address for data segments Routing takes place here; the best path for data delivery is determined here IP, routers Layer 2: Data Link Performs physical addressing (MAC) MAC address of the source and destination of the data is added to the data packet to create a frame This enables the frames to be transported physically via a local medium like copper wire MAC Layer 1: Physical Converts the binary code produced by the above layers into signals (electrical/light/radio) and transmits them over local media Responsible for sending computer bits from one computer to another 29  Short summary ⑦ Application = network process to application ⑥ Presentation = data representation & encryption ⑤ Session = interhost communication ④ Transport = end-to-end connections & reliability; logical addressing ③ Network = path determination & IP addressing ② Data Link = physical addressing ① Physical = signals sent through media ○ Packets Created in the network layer (layer 3) Allow routers to send/receive data across the internet Structure Header: contains info about the data carried by the packet, like packet length packet number and source & destination IP address Payload/Body: the actual data being transmitted, it is fixed in length but may contain blank info to make it the right size Trailer/Footer: bits that tell the receiving device that the end of the packet has been reached ○ Frames Created in the data link layer (layer 2) A frame is an encapsulated packet Ethernet frames have an additional header contains the receiving and sending devices’ MAC addresses to deliver the payload to a location on the same network FCS (Frame Check Sequence) detects errors in data transmission added in the footer of a frame 30  ○ VLAN (Virtual Local Area Network) Devices that communicate frequently within a LAN form a virtual LAN Improves the overall performance of the network by isolating traffic for each VLAN It is based on logical connections; not necessarily physical VLAN Tagging = method that allows LAN switches to distinguish between physical groups of LAN ports and logical groups of LAN ports WLAN (Wireless Local Area Network) ○ LAN with no cabling ○ Offers a temporary connection to an existing, cabled network ○ Provides portability; you can move freely while staying connected ○ Useful for mobile networks ○ Wi-Fi = wireless LAN technology ○ Devices: Wireless Access Point (WAP) A fixed position wireless transceiver (transmitter/receiver) that broadcasts signal in a area (microcell) The access point connects to a wired backbone for network services Devices can thus connect to a wired network, wirelessly Wireless Bridge Component that offers an easy way to connect network segments without cables e.g. Linking buildings that are separated by a road Wireless Router Allows multiple networks to join the same network Provides access to the internet Can function as a switch, access point and Internet router 31  ○ Wi-Fi = a facility allowing devices to connect to the internet or communicate with one another wirelessly within a particular area ○ Hotspot = site that offers internet access over a LAN using a router or WAP to link to an ISP (Internet Service Provider) Bounded vs Unbounded Connections ○ Wi-Fi is more convenient ○ Speed: Ethernet > Wi-Fi ○ Reliability: ethernet is more consistent ○ Security: data needs to be encrypted for Wi-Fi; ethernet doesn’t require encryption ○ Latency: Wi-Fi > Ethernet ○ Deployment: easier to install Wi-Fi, less cabling and infrastructure Extending a LAN - Fibre Optic Backbone ○ Connects various parts of a network ○ A path for the exchange of information between LANs ○ Fibre optic is preferred because of its speed and lack of attenuation Centralised vs Distributed Processing in a LAN ○ Centralised Network Single server, responsible for some or all of the processing Less powerful workstations are connected to the server (thin clients) Server is used for applications and data storage ○ Decentralised Network Workloads are distributed among several machines instead of a single server Clients are more powerful ○ Distributed processing System utilises more than one processor/computer to run one application Idle CPUs on the network are detected, identified and then tasked with the processing of programs ○ Thin Clients Desktop terminal/workstation without a hard drive 32  All data is stored on a server to which the thin client is connected (centralised network) Advantages: lower cost, easily manageable, secure ○ Fat clients A node/computer with most of its software installed locally (some network resources are not although) Allows customisation and configuration for individual users Advantage: less network traffic ○ Smart Clients Applications’ data is mostly stored remotely and can be accessed via the internet Uses the processing of the local drive e.g. YouTube, Google Drive Not web-based apps, they contain features that are absent in browser apps; they use network data but aren’t dependent of it WANs WAN (Wide Area Network) ○ a collection of LANs or other networks that communicate with one another ○ Not confined to one area ○ Usually employs 3rd parties to provide connections to WAN, e.g. public telephone systems ○ Satellites, microwaves and optic fibre is used to connect parts of WANs; these connections are external and must be paid for Devices ○ Gateways Device that provides connection between two or more network segments Also called protocol converters; they can operate at any network layer, usually between 2 protocols 33  A router can act as a gateway between two networks with the same protocol When the protocols differ, an actual gateway is needed to repackage packets and frames for the different protocol ○ Wi-Fi Router Most wireless routers have at least two ports: one WAN port and one or more LAN ports the WAN port connects to a high-speed modem, like a DSL or cable modem, which in turn connects the router to the Internet The modem connects your home to the Internet, while a router creates the network inside your house Transmission ○ Satellite Radio Waves In geostationary orbit Satellite communications are available globally and large distances are easily covered Very reliable and secure Expensive start upland data cost Can transmit a high amount of data ○ Microwave Electromagnetic waves in the microwave frequency range used to transmit video/audio/data between 2 locations Can be over a few metres or several kilometres Internet Connection Technologies ○ Cellular Technologies Mobile phone networks consist of signal area called cells In a cell there is a base station/mobile phone tower that creates coverage for a large area Devices will connect to the closest, least congested tower and the connection will be passed to the next tower if one moves out of range 34  3G (3rd Generation) Improves data transfer for formats like: standard HTML, videos, music Slow speed LTE (Long Term Evolution) Slight improvement over 3G; 4G LTE is a major improvement though 4G Higher speeds than 3G 5G Smarter, faster and more efficient than all the above Low latency Shorter wavelength, means that are more base stations needed for a reliable connection ○ Wi-Fi Calling Make phone calls over the internet with no data cost Useful for when a cell network has no service, but you have Wi-Fi e.g. Facebook, WhatsApp, FaceTime ○ Fibre: optic fibre cables are used to transmit data; a little loss of signal can occur over long distances ○ ADSL (Asymmetric Digital Subscriber Line) Telephone line used to transmit data along its copper cables Slowly being replaced by optic fibre ○ Fibre vs ADSL Fibre ADSL Superfast broadband More internet traffic, Can handle great thus slower speed volumes of traffic Further from Distance from exchange of data, exchange is irrelevant thus slower speed for speed 35  Bandwidth (Mbps/Gbps) ○ The maximum amount of data your connection can handle at any moment ○ Amount of data that can be transmitted from one point to another in a given amount of time Internet Speed (Mbps/Gbps) ○ The maximum rate you can transmit data ○ Rate at which data travels from the web to yours device; upload speed is lower than download speed Protocols ○ Email SMTP (Simple Mail Transfer Protocol) When email is delivered from a client to an email server, or when an email is exchanged between servers Usually used for outgoing mail POP3 (Post Office Protocol) Allows client to download an email from an email server Offers no other features; download only IMAP (Internet Message Access Protocol) Similar to POP3 but has more features ○ Web HTTP (HyperText Transfer Protocol) Standard protocol for transferring web pages across the internet HTTPS HTTP over a Secure Socket Layer (SSL) Secure version of HTTP; safe for info like password or bank credentials HTTPS websites require a Certificate of Authority issued by a 3rd party 36  ○ Download FTP (File Transfer Protocol) Used for the transfer of files over the Internet WebDAV (Web Distributed Authoring and Versioning) Used for communication between client browsers and web servers Cloud Computing as an extension to a LAN Sharing concepts ○ Client-server model Data is hosted on a remote server and is shared when requested by a client on the network; it is traditional and centralised Leeching = downloading only ○ Peer-to-Peer (P2P) Every computer acts as a server; not only the server delivers files but each computer does; it is decentralised Seeding = computers can share data to others (seeding vs leeching) Advantages Easy file sharing Lower cost; no cost for a server Reliable: if a centralised server crashes there is disruption, no server means no huge disruption High performance: more clients will improve the network performance, since more nodes will then contribute to sharing Disadvantages Less security: files are sharable without noticing Many risks for the spread malware BitTorrent P2P protocol Torrent = file downloaded piece-by-piece, from all computers containing the pieces of that file, and then reassembled 37  Large file split into smaller parts on several computers for faster upload BitTorrent Swarm = a group of computers uploading/downloading the same torrent BitTorrent tracker ○ Type of server aiding in the communication between peers using Bittorrent protocol ○ It keeps record of machines’ file copies and helps to coordinate efficient transmission & reassembly Torrenting is not illegal but has an illegal reputation due to copyrighted material found on theses sites ○ FTP is not part of P2P; it falls under a client-server model ○ Through WebDAV, collaborative editing of remote file can take place Sharing to remote sites ○ Remote Access Accessing files that is not on your computer’s local hard drive vis a network One interacts with another device’s interface/screen without using that device itself e.g. TeamViewer ○ VPN (Virtual Private Network) Data sent in a highly encrypted and secure tunnel Connect to a private internal network remotely, using the internet Used for: Protection: a device using a VPN is essentially invisible for the rest of the internet Anonymity: IP address is changed while using a VPN Access of media: one can access media that isn’t available in your country by using a VPN VPNs protect your traffic from government surveillance, ISP snooping and hackers 38  Remote Access Virtual Private Network (VPN) Advantages User can utilise an entire Can join a network remotely computer remotely and utilise resources like Money can be saved since printers less commuting is Many affordable VPN necessary if users can services work remotely Offers security; masking IP, Many free remote access hiding your location, software is available encrypting data Can access benefits that aren’t available in your location, e.g. cheap flights Disadvantages Risk of malware VPN service provider may Strangers may be able to keep usage logs and collect access your data information about you Leaks can occur is configuration is poorly encrypted Internet of Things (IoT) ○ System of related devices, machines, animals and/or people provided with unique identifiers and the ability to transfer data without human intervention ○ ‘Things’ refer to objects that contain data, like a person with a pacemaker or a dog with an ID chip ○ IoT is widely used in manufacturing, transportation, agriculture and home automation ○ e.g. on farms: collection of rainfall, livestock population & identification ○ Advantages: Saves time and money Improves quality of life Saves paper Improves quality of service if used in businesses ○ Disadvantages: Replaces jobs Management of a large amount of devices can be complex 39  No international standard for IoT, therefore communication between foreign systems can be a challenge More information on a system increases the risk of it being stolen The Internet/Web Internet is a global network that offers basic services like emailing and web browsing Reason for an IP address: ○ to handle the connection between devices that send and receive information across a network. ○ IP addresses uniquely identify every device on the internet; without IP addresses, there's no way to contact devices Ways to connect to the internet ○ SIM Cards (subscriber Identity Module) Computer chips that hold information and allow you to connect with your cellular network Smart card that stores identification information that pinpoints a smartphone to a specific mobile network ○ Wireless/Wi-Fi router Most wireless routers have at least two ports: one WAN port and one or more LAN ports the WAN port connects to a high-speed modem, like a DSL or cable modem, which in turn connects the router to the Internet The modem connects your home to the Internet, while a router creates the network inside your house ○ Personal Hotspot Site that offers internet access over a LAN using a router or WAP to link to an ISP (Internet Service Provider) ○ ADSL Router Telephone line used to transmit data along its copper cables Slowly being replaced by optic fibre 40  Multimedia Online ○ Multimedia = combination of text, graphics, audio and video that lets users navigate, interact, create and communicate through the internet ○ Download = the process of receiving data from a remote server to a computer; a copy of the file is stored in the storage of the computer ○ Streaming Process of delivering data continuously through the internet in real time Buffer = small wait before streaming starts; the slower the internet speed, the longer the buffer ○ It is better to download files than to stream them if your network is slow ○ On Demand = you can decide what you want to see/hear and when you want to ○ Video On-Demand (VOD) Audio & Video On-Demand (AVOD) Systems that allow users to select and watch/listen media they wish to Offers streaming and downloading Can be pay per view, e.g. BoxOffice Can be Internet TV, e.g. Netflix, Amazon Prime, Hulu ○ VoIP (Voice Over Internet Protocol) Transmission technology involved with the delivery of voice and multimedia data using an IP network like the internet Traditionally: PSTNs were used (Public Switched Telephone Network) Nowadays: VOIP is used for services like voice/text messaging e.g. Zoom, Skype ○ Podcast/Vodcast Vodcast = podcast with video content Series of on demand audio, focused on a specific topic/theme Podcasts are portable, since they are available on your phone 41  Compression Technology ○ Encoding data so that it can be transferred using fewer bits ○ Data Compression = reducing the size of a data file ○ Lossy Identifies and eliminate statistical redundancy Trade off between information lost and size reduction Used in music, images and videos JPEG = compression for digital images that rounds off less important visual info MP3 = patented encoding format used for digital audio MPEG - 2 = used for videos ○ Lossless No information is lost and the size of the original file is restored e.g. ZIP ○ Lossy: Compression of Audio Files To represent a sound wave digitally requires the sound to be broken into thousands of samples per second, each sample is then stored as a binary value Sample Rate Number of audio samples captured every second More samples means higher audio quality VoIP can be as low as 8kHz which is an acceptable frequency for voice, but music at this frequency will be of poor quality Bit Depth Number of bits allocated to a sample More bits allocated means a higher audio quality Bit Rate Number of bits processed per second (kbps) Bit rate determines the quality of the file encoded in audio format 42  Lower bit rate means more information will be discarded during compression MP3 Compression Music was originally distributed on vinyl records, 8-tracks and cassette tapes. These signals were analog Analog files that were converted to be digital are very large files in size; compression was thus required Uncompressed AV or AIFF files: 30MB for a 3 minute song Compressed (MP3): 3MB for a 3 minute song and minimal loss of quality MP3 removes sound we can hear; sounds between 16-18kHz When sounds occur close to one another, only the loudest sound will be retained If sounds occur simultaneously only the loudest will be kept ○ Quality vs Bandwidth and Speed Higher quality means that the speed of the transfer of the file will be slower ZIP files: Folder compressed to a single file File (folder) is then sent/downloaded using less bandwidth When decompressed, all files can be viewed as they were before compression Beyond the Indexed Web ○ Browser = software that retrieves and displays web pages, e.g. Chrome, Safari ○ Search Engine = website that helps users find web pages from other websites, e.g. Google, Bing 43  ○ Surface web Part of world wide web Indexed (searchable) through standard web search engines ○ Deep Web Not indexed by standard search engines Contains information like medical records, fee-based content and confidential, corporate web pages 90% of the internet is the deep web ○ Dark Web Not indexed by standard search engines Intentionally hidden from search engines and the public Only accessible through special web browsers Hub for illegal activity e.g. Sale of drugs and firearms, hiring services for hitmen and hackers as well as botnet rentals Not only used for illegal activity though: the dark web is sometimes used for privacy by journalists and politicians 5% of the internet Anonymous Browsing Tools ○ Onion Router Messages/data is surrounded by several layers of encryption Connection isn’t directly to destination, it travels through several nodes first, thus leaving no trace Tor (example of an onion router) Open source software providing anonymous connection to the internet Consists of many relay nodes that implement onion routing Tor relay nodes create the connection between the Tor client and the destination server Relay refers to the message being encrypted/decrypted layer by layer as it is passed to the next node (like in athletics) 44  ○ VPNs are also used for anonymous browsing thanks to IP address masking and online anonymity that its services usually offer (see prior) Evolution of Internet Service Technologies ○ Web 1.0 Static sites Users could only view pages Unless they were developers they couldn’t contribute to the content of the page Few users used the web at this stage ○ Web 2.0 Start of dynamic sites Users could interact and communicate with these sites User generated content started: social networks, wikis and blogs Improved user interface, software and data storage It provided fast and efficient ways to share content It enables users to receive real-time notifications ○ Web 3.0 Provides a more personal experience for users Results for the exact same query may differ from user to user E-Commerce and advertising is much more customised to the users preferences ○ Web 4.0 Mobile web The web will adapt to the users surroundings ○ Cookies Small piece of data sent from a website and stored in a user's browser When that website is accessed again in the future, the cookie is retrieved and the website is notified of the user’s previous activity 45  Privacy concern: tracking cookies and third party tracking is often used as ways to compile records of individuals’ browsing history Scripting ○ Script = set of instructions ○ Client-side scripting Web pages change after they arrive at the browser JavaScript is commonly used for client-side scripting Process: User requests a page from a server Server sends the page to the user Page is displayed with scripts running during/after the page is displayed Scripts sometimes don’t run if the machine can’t understand its language and slow computers will have slow scripting ○ Server-side scripting Enables users to make personalised accounts and gives them a level of privacy e-Commerce and social networking rely heavily on server-side scripting Process: User requests a web page from the server Script in the page is interpreted by the server Changes are then made to the page’s content to suit the user/occasion before the user receives the page The page is the sent to the users, in its final form, and further changes can’t be made Server-side scripting is never seen by users; it affects the server’s performance, but not the client’s system performance ○ Combination of server-side and client-side scripting Server handles logging in and preferences of user Client can then sort and display content they wish to e.g. Google, Amazon, Facebook 46  Web-Based Applications ○ Software that runs on a web browser ○ Only an internet connection and a web browser is required ○ Web-based application are installed and run on remote servers that are accessed by a user’s web browser ○ Advantages: No installation process, software isn’t hosted on a user’s computer Easily accessible, no need for special software The applications aren’t limited by the OS of the computer The apps will be kept up to date better and no update checking is necessary as one would with desktop applications ○ Examples: Email apps, word processors, spreadsheet apps etc. e.g. Google’s suite of office productivity tools: Google Docs, Google Sheets, Google Slides or Microsoft Office: Office Online & Office 365 Mobile Applications ○ Native Mobile Applications (platform specific) Apps are written using the native development language and tools specific to the platform of the device e.g. iOS uses Swift or Objective-C, compiled using Xcode. Android uses Kotlin or Java, compiled using Android Studio Advantage: a better performance and better user experience, since the app is written in code that is designed for the device Disadvantage: apps must be designed per platform, like iOS and Android , this can be costly and time consuming ○ Mobile Web Applications Applications for mobile devices that require only a Web browser to be installed on the device they use Web technologies and are not limited to the underlying platform for deployment e.g. The Pinterest App, Amazon.com, Alibaba.com 47  ○ Hybrid Mobile Apps (platform independent; not platform specific) A blend of native and web solutions Core of the app is written using cross platform technologies, like HTML, CSS or JavaScript Plugins are sometimes included to access specific features of the specific devices Plug-Ins & Extensions ○ Plug-In Software module that adds special features to an already existing program, to customise that program Always executable code e.g. Adobe Flash Player (videos), Java Virtual Machine (applets) Discouraged nowadays; extensions are preferred ○ Extension Software module that offers customisation for web browsers Widely used; more than plug-ins Usually source code e.g. Password management, ad blockers, cookie management Design Factors for Mobile Technology ○ Screen Sensitivity to touch will affect how a user interacts with an app/website Quality of the screen resolution: higher resolution = more power intensive ○ Processing Demands Mobile device process power is ever changing; the developer must thus find an average and work with that ○ Storage Demands Mobile device have limited storage; storage design must be efficient ○ Bandwidth requirements Does the app require location-based services or other bandwidth intensive features? 48  Mobile Positioning & Services ○ GPS (Global Positioning Service) Satellite based navigation system made up of at least 24 satellites Works 24 hours a day, in any weather conditions, with no cost ○ LBS (Location Based Services) The geographic location of a device is used to provide contextual information, like the closest ATM or restaurant Mostly uses GPS-technology and cell towers Used for: Store and service locators Proximity based marketing, certain ads are pushed in certain locations Travelling information: traffic updates, weather reports Social networking: adding a location to a post Cloud Computing ○ The practice of using a network of remote servers hosted on the internet to store, manage, and process data, rather than a local server or a personal computer ○ Lower cost, more efficient and flexible ○ Cloud Storage Hardware in a remote location stores data than can then be accessed via the internet Auto scaling: you only pay for what you need Types: personal, private (company data), public (like DropBox) Google Drive, iCloud and Dropbox are examples of cloud storage Advantages: Easily accessible Data isn’t lost if hardware is stolen Hard drive space is saved when cloud storage is used 49  Disadvantages: Unreliable internet connection means an unreliable access to storage Data can be easily lost/stolen if it is not properly encrypted ○ Cloud Applications Unlike web-based applications it is not totally reliant on a browser, although it needs a web browser to run More evolved than web-based applications A web application or web-based application must have a continuous internet connection to function A cloud application performs processing tasks on a local computer or workstation. An internet connection is required primarily for downloading or uploading data Google G Suite vs Microsoft 365 Google G Suite Microsoft 365 Overview Less complex; ideal for Has complex functions basic functions Ideal for businesses with Ideal for small businesses complex problems Advantages No limit on the maximum Users are on average more amount of users familiar with Microsoft Less costly Internet is not essential to OS independent use Microsoft 365 Products can be used offline Disadvantages No desktop version for G Complexity of some Suite products may overwhelm Some products have less the user functionality Some Products are specifically designed for Windows OS NOTE: Microsoft Office 2019 = desktop apps with a one time licence, documents are saved on the local drive Microsoft 365 = monthly subscription; files stored in cloud 50  Licencing ○ Subscription licences Month-to-month or annual payments that allow users to access certain service ○ Pay-as-you-Go licences Only pay for the amount of the service that you use e.g. Only pay for the amount of cloud storage that you use ○ Educational licencing Licences are free for educational institutions Schools register a domain with Google to access free resources like Google Classroom Ownership & Permission ○ Google If a user creates files and uploads them to a shared drive, they belong to the organisation Private data should be stored in private accounts and company related data should be stored in the shared drive of the company ○ Microsoft Files and folders created by a user belongs to the user, but the administrator can change the ownership of these files between users (Google follows this too) Security Services ○ Public and private key Asymmetric pair of keys for encrypting and decrypting data Private keys can be used for both encryption and decryption Private keys are shared between the sender and the receiver Public keys are used only for the purpose of encrypting the sensitive data. Public keys can be freely circulated among multiple users A user shares a public key to allow anyone who wants to send them information to encrypt it with that public key This message is then decrypted by the user’s corresponding private key once information has been sent Digital signature = when a user “signs a document” by encrypting it with their private key ○ Digital Certificate Also called SSL or TLS Certificates It is a data file issued by a Certificate of Authority (CA) to an organisation, to acknowledge the identity of the organisation Just like passports have photos along with personal info; a digital certificate binds a public key to information about its true owner Certificate includes: domain name, certificate validity period, CA details, public & private key ○ SSL (Secure Socket Layer) Protocol for managing security when transmitting data on the Internet 51  ‘https://’ ensures that you are on a safe website TLS (Transport Layer Security) = the most commonly used and the most advanced cryptographic protocol ○ SSL Communication SSL Handshake = An interaction between the server and client where SSL information is shared A client reviews the server’s SSL certificate to authenticate the server, an authentication error would lead to SSL connection being refused If a connection is established, the client creates a session key and encrypts it with the server’s public key and the clien