Title: Year 12 / Computer Science / Theory / 2 - Communication / 2.1 - Networks including the network

Q: Describe what is meant by the "world wide web".
A: the huge collection of documents, such as web pages, images etc that can be accessed using the internet

Q: Describe what is meant by the "internet"
A: the biggest interconnected network in the world, which is used to access resources online

Q: Describe what is meant by a "web browser"
A: a software which allows you to view content on the world wide web, such as web pages, images and videos

Q: Describe what is meant by a "protocol"
A: a set of rules which governs the transfer of data between computers. allows computers to work together

Q: State the purpose of networking devices
A: they are interconnected devices that allow a fast means of data transmission within the network

Q: State the benefits of networking devices
A: can easily share data and files between interconnected devices
resource sharing, using network connected output devices like printers, or sharing software within the network
higher storage as files can be stored in network connected storage mediums

Q: Explain what is meant by a LAN
A: local area network that connects devices within small geographical area, has only private ownship, transmits data through twisted pair cable, coaxial cable or wifi, has high data transfer rate, has low congestion

Q: Explain what is meant by a WAN
A: network that connects devices within large geographical area, can have private or public ownership, transmits data through PSTN or satellite link, has low data transfer rate, has high congestion

Q: Explain the client server model
A: there is a dedicated server that holds data and performs requested processes, clients are individual computers that send requests to the server, which returns results of requests

Q: Explain the peer to peer server model
A: decentralised network where each connected computer stores data and operates independently as a peer, can act as both a client and server

Q: State 2 applications of peer to peer network models
A: internet and ad hoc networks

Q: State and explain 5 examples of client server network models
A: printer server, where printer manages print jobs from client computers
file sharing server, clients accesses software and users data files are stored on server
email server, for sending, receiving or storing emails
data base server to manage DBMS
domain controller server, where server does management of user accounts, (ids and passwords) and the client sends login request to the server which processes and grants request if user ID and password recognised, proxy server

Q: Describe the benefits of the client server model in contrast to a peer to peer model
A: has centralised backup, files and resources are centralised in server to prevent illegal resource usage, has better security, as files are stored on central server which gets scanned for malware

Q: Describe the benefits of the peer to peer model in contrast to a client server model
A: has less initial set up cost, lesser network traffic as each peer can simultaneously receive data from different sources, can work even if a device goes down

Q: Describe what is meant by a "thin client"
A: client that solely runs on the resources provided by server, has no local storage,
only provides input and receives output as processing done by server,
smaller purchase cost as expensive demanding hardware not required,
improved security as cant run unauthorised, harmful software

Q: Describe what is meant by a "thick client"
A: an independent client that doesnt require server to run,
processes most of the application,
can function even if no server is connected as can work offline,
no lag related to network problems

Q: Describe how wired networks work
A: they use copper (twisted-pair or coaxial) cable or fibre optic cables connected to an ethernet port on the network router

Q: Describe the benefits of copper cable
A: cheaper,
easier to install,
flexible,
easier to make terminations

Q: Describe the drawbacks of copper cable
A: doesnt perform well with small charges, affected by electromagnetism

Q: Describe the benefits of fiber optic cables
A: greater bandwidth,
improved security,
lightweight so easy to install,
less signal boosting required,
used in long distance communication

Q: Describe the drawbacks of fiber optic cables
A: needs expensive optical transmitters and receivers

Q: Describe how a wireless network works
A: use radio waves, microwaves, satellites to connect devices to networks without cables

Q: Describe the benefits of using radio waves for wireless networks
A: can travel larger distance as they have largest range of wavelength,
cheap,
used for tv signals and mobile phone comms

Q: Describe the drawbacks of using radio waves for wireless networks
A: low frequency so transmits less data at once, affected by radio stations with similar frequency

Q: Describe the benefits of using microwaves for wireless networks
A: larger bandwidth, can transfer more data at once

Q: Describe the drawbacks of using microwaves for wireless networks
A: emitting towers expensive to build
physical obstacles can interfere

Q: Describe the benefits of using satellites for wireless networks
A: cheap with long distance, used for satellite phones, satellite radio broadcast

Q: Describe the drawbacks of using satellites for wireless networks
A: easy to interfere with, expensive to set up

Q: State the 4 types of network topologies
A: bus, star, mesh, hybrid

Q: Explain how a bus topology works
A: single line (bus) that connects all the devices with terminators at each end, other computers can read the data being sent between computers, unsuitable for heavy traffic since collisions occur

Q: Explain how a star topology works
A: consists of a central server called a switch, which has a dedicated connection to all other computers, so server can send packets to different devices simultaneously and bidirectionally, no collisions possible

Q: Explain how a mesh topology works
A: network setup where every device (called a node) is directly interconnected to every single other device, usually used for wireless networks like the internet via mesh connection of routers

Q: Explain how a hybrid topology works
A: combination of two or more topologies, eg connection between 2 or more LANs of different topologies

Q: Explain what is meant by cloud computing
A: on demand provision of computing services through the internet, such as infrastructure like storage capacity and higher processing power, and a platform for software, testing and debugging resources

Q: Explain what is meant by public clouds
A: owned by 3rd party cloud service provider which grants access to multiple parties and is accessible through browser, the provider owns, develops and manages the public cloud through large server farms

Q: Explain what is meant by private clouds
A: private cloud is owned by one organisation and not shared with other organisations, it can be created and maintained by organisation itself or can outsource this work 3rd parties

Q: State the benefits of cloud computing
A: less technical knowledge required, easy to implement, flexibility as cloud can be scaled to match organisation's growth

Q: State the drawbacks of cloud computing
A: cant access resources/data stored on cloud if theres bandwidth issues, poor data privacy as there can be data leakage in the multi tenant architecture (public clouds)

Q: Explain what is meant by the world wide web
A: collection of web pages stored on websites, protocols are used to transmit data across the www

Q: Explain what is meant by the internet
A: its a massive open network of networks, uses TCP/IP protocol which uses IP addresses to identify devices connected to the internet, access provided by ISP, uses wired, radio and satellite communication

Q: Describe the role and function of a router in a network
A: connects 2 networks together which might operate on different protocols, allows internal connections between LANs or allows external connection from main LAN to WAN, acts as gate and firewall, usually attached to server or switch in a LAN, translates private IP addresses to public IP addresses and vice versa

Q: Describe what a URL is
A: unique reference address for exact location of an internet resource on WWW

Q: Describe what is meant by DNS
A: naming system used for computers and resources that have internet connection, consists of hierarchy of DNS servers which have URLs database and their corresponding IP addresses

Q: Name 8 examples of hardware that are used to support a LAN
A: switch, server, network interface card, wireless network interface card, wireless access point, cables, bridge, repeater

Q: Explain what is meant by ethernet
A: most common wired medium of transmission, can be used to transfer data between LANs or WANs, usually used in bus topology

Q: Explain why data corruption is a risk in ethernet connections
A: ethernet is usually used in bus toplogies, and since all data travels on a single wire, theres chance of data corruption by collision of signals

Q: Explain how collisions in an Ethernet connection are detected and avoided
A: CSMA/CD, before transmitting, device checks if channel is busy, if it is, device calculates random wait time and waits for that time, after which it begins transmission, during transmission, device listens for other devices also beginning transmission, if collision happens, transmission gets aborted and both devices wait different random times, then transmission is tried again

Q: Describe what is meant by a switch and how it supports a LAN
A: connected to all devices in a LAN and can simultaneously broadcast information to all devices

Q: Describe what is meant by a server and how it supports a LAN
A: device or software that provides specific function for computers in the network

Q: Describe what is meant by a network interface card and how it supports a LAN
A: provides each device in wired LAN with a unique MAC address to uniquely identify it on the network, allows each individual device to connect to the network

Q: Describe what is meant by a wireless network interface card and how it supports a LAN
A: provides each endsystem of a wireless LAN a unique network address to identify them

Q: Describe what is meant by a wireless access point and how it supports a LAN
A: allows devices to connect to LAN via wifi instead of cable, usually built into router

Q: Describe what is meant by a cable and how it supports a LAN
A: wired transmission medium that allows communication in wired networks

Q: Describe what is meant by a bridge and how it supports a LAN
A: connects 2 LANs which use the same protocol and can be 2 segments of the same network, stores network addresses for all devices between the 2 networks, looks for the receiving device before it sends a message

Q: Describe what is meant by a repeater and how it supports a LAN
A: connects 2 cables, regenerates the sent data signal over the same network before the signal weakens to prevent it from being corrupted

Q: Explain what is meant by bit streaming
A: sequence of digital signals transferred over a communication path at high speeds, requires fast broadband connection and form of buffers, the bits arrive in the same order theyre sent

Q: Explain what is meant by bit rate
A: number of bits transmitted per second

Q: Explain what is meant by the method of real-time bit streaming
A: event is captured live on camera and connected to computer, video signal is converted to encoded stream video signal, which is uploaded from computer to a streaming server by cables or fast wireless internet connection, server sends live images to users requesting it as a real time video, cant be paused or fast forwarded

Q: Explain what is meant by the method of on-demand bit streaming
A: existing digital files get coverted to encoded bit streaming format for  internet broadcast by uploading to server, link for encoded video is put on website and user clicks to view encoded streaming video, data is streamed to buffer in users computer, which stops video being paused as bits are streamed, buffer gets emptied and filled again to provide continuous viewing, can be paused, fast forwarded etc

Q: Explain the impact and importance of a high broadband speed and bit rate on bit streaming
A: user has to download and display bits at same time, so if media is higher quality, then higher broadband speed is needed as each frame is larger size,
real time needs faster broadband speed than on demand, since more users requesting the same data at once

Q: Name 4 different internet-supporting hardware
A: modems, pstn, dedicated lines, cell phone network

Q: Describe what is meant by a modem
A: allows device to conect to internet by telephone line, used by transmitter to convert digital signals to analogue signals that are sent down telephone line, receiver uses a modem on other end to convert analogue signals to digital signals so it can understand data

Q: Describe what is meant by PSTN
A: public switched telephone network, refers to all telephone networks, channel used between 2 endpoints for the call duration by circuit switching, lines are active even during power outage, able for bi directional communication

Q: Describe what is meant by dedicated lines
A: telecommunication path between endpoints, not shared with multiple users, is only bought or leased, able to host websites and phone calls, allows continuous uninterrupted access on web

Q: Describe what is meant by a cell phone network
A: wireless network spread over land areas divided into cells, each served by 1 base station which uses different freq range, compared to adjacent cells, to transmit data,
larger capacity possible since same frequencies can be used in non adjacent cells,
radio waves usually used for transmission,
can be broadcast in all direction over wide area,
has portable transceivers like mobile phones that can communicate and access internet via base stations

Q: Describe the differences between the format of an IPv4 and IPv6 address
A: ipv4 is 32 bit split into 4 blocks by ., each block can have value between 0 and 255 or 00 to FF in hex, ipv6 is 128 bit split into 8 16 bit blocks by :, each block can have 4 hex values from 0000 to FFFF, can be shortened by removing > or = 2 blocks that only contain 0s

Q: Explain how an IPv4 address functions
A: each ip address has 2 parts, which has a network identifer/netID which identifies the network the host device is connected to, and host identifier/hostID which identifies the host within the network,
ipv4 uses classful addressing where different bit lengths are used for identification and impose restrictions on available host addresses

Q: Explain how subnetting works
A: its dividing a network into 2 or more networks, ip address gets broken into 3 parts where host id is split into subnet id and host id, subnet id bits are used to identify each subnet in the network, subnet masks are number that hide the netid of systems ip addresses and only leaves the host part as machine identifier, which allows data to be routed within subnet to appropriate host

Q: Describe the differences between a public and a private IP address
A: public issued by ISP, private issued by lans router, public is unique and can be accessed across internet, private is only unique and accessible within lan, network address translation required for private to access internet directly, private more secure than public as not directly accessible on internet and hidden by NAT, range of ip addresses used for private can never be assigned to public

Q: Explain what is meant by a static IP address
A: ip address never changes, useful when websites need to remember a device for a long time, like VPNs whitelisting, faster upload and download speeds

Q: Explain what is meant by a dynamic IP address
A: will change at regular time periods, more secure than static, so used where data privacy is important, maintaining cost is lesser