Networks & the Internet (Cambridge (CIE) A Level Computer Science): Flashcards

A WAN is a network covering a large geographical area, over 1 mile, made up of a collection of LANs joined together and connected via routers.

The computers on a wide area network are connected via routers.

Fibre optic cable, telephone lines and satellite.

False.

On a WAN the connecting hardware is not all owned by the organisation — telephone lines, for example, are owned by telecommunication companies. On a LAN, all the hardware is owned by the user.

If hardware fails the network may not function, networks are more prone to attacks than standalone computers, access can be slow depending on network traffic, and they require costly maintenance.

A client-server network is one where powerful, reliable server computers control the network and 'serve' the clients with services such as files, email and web access.

It hosts, delivers and manages most of the resources and services to be consumed by the clients.

Easier central management, scalability since new clients can be added easily, and higher reliability because resources are managed centrally.

It is a single point of failure — if the server goes down services could be unavailable — and it is expensive to set up and maintain, often needing dedicated teams.

Larger organisations where centralised control is needed and reliability and security are paramount.

A peer-to-peer network is the simplest type of network, where all computers share equal responsibility and there is no central server.

Each machine is the responsibility of that machine's own user, and data is spread around the network with each user responsible for their own.

The lack of central control can lead to security issues and vulnerabilities, and it is not suitable for large networks because of performance issues.

Web pages and files are saved on servers; clients send requests to the web servers, which process the requests and return the results to the client, and the client displays the results to the user.

A thin client relies on a permanent connection to a server to function, depending on the processing power of another computer or server.

A thick client works independently without needing a constant connection to a server, using the processing power of its own device.

A thin client cannot function without being connected to a networked computer or server.

Cloud-based applications, remote desktop software, and supermarket point-of-sale systems connected to a central server for prices, stock and payments.

A thin client is best for centralised control, low-cost devices and shared environments, while a thick client is best for performance, flexibility and offline access.

False.

A thick client may connect to a network for updates or data sharing, but it is not reliant on one and can function offline.

A network topology is the physical structure of the network, defining how the network hardware is arranged to create it.

All devices are connected by one single 'bus' cable, which is terminated at each end.

They stop the signal bouncing back and causing errors.

Each device 'listens' to electrical signals, checks data packets for its specific address, and ignores packets it does not recognise.

Low security, since data is visible to all devices; slow data transfer, since it is prone to data collisions; and if the cable breaks the whole network is affected.

It is easy and cheap to set up, since only one cable is needed, and it does not rely on other network hardware such as a central server or switch.

All devices connect to a central switch, which is an intelligent device that ensures traffic only goes to the intended device.

A hub sends traffic to all devices, and each device accepts it only if the address matches; a switch only sends traffic to the device whose address matches.

If one cable fails the rest of the network still works, a problem with one device will not affect others, and it is more reliable than a bus topology.

On a star topology the central switch is a single point of failure.

A topology where all computers are connected to all other computers.

Routing, where devices are given routing logic to send packets by the shortest route, and flooding, where all packets are sent to all devices with no routing logic.

If one cable fails the network still works because data can use an alternate route, it provides high fault tolerance through multiple paths, and it is very reliable for critical systems.

It requires lots of hardware, cables and switches, has a high cost to set up, and is hard to scale because adding new devices is complex.

A hybrid topology is a mix of two or more different network topologies, typically used when there is a need to join different networks together.

False.

Troubleshooting can be harder because different parts use different systems and rules, and it is also complex to design and expensive.

Cloud computing is when software, services or files are hosted entirely on remote servers and accessed through the internet.

Cloud storage and cloud software.

Cloud storage is long-term storage of data that resides in a remote location, accessible only via the internet, with data held on remote servers in data centres.

Usually HDDs, which are magnetic, but increasingly SSDs, which are solid state.

Maintenance, upgrades and security.

Cloud software is typically paid for via a monthly fee or yearly subscription.

Accessibility from anywhere with an internet connection, easy sharing and collaboration, scalability as storage can be increased or decreased, reliability since data is backed up across multiple servers, security features such as encryption and multi-factor authentication, no need to buy expensive storage hardware, no need to hire specialist IT staff, and it is eco-friendly.

It needs a reliable internet connection, it can be expensive for large amounts of data, there are ongoing subscription costs, there may be charges for extra data transfer, there are security risks since data could be intercepted, and the user has less control.

Centralised data centres are more efficient than millions of local servers.

It is accessible anywhere on any device with internet, no installation is needed, there are automatic updates, maintenance is handled by the provider, it is scalable, security is included, and it often works across multiple devices.

It needs internet access and will not work offline, performance depends on internet speed, there are ongoing costs, there are data privacy concerns, the user has less control over when updates happen, and some features may be limited compared with a locally installed version.

In a public cloud they are owned and managed by a third-party provider; in a private cloud they are owned and managed by the company itself.

In a public cloud services are shared with other organisations or users, while in a private cloud access is restricted to that company.

The company pays for its own hardware, maintenance and staff, whereas a public cloud's shared infrastructure reduces cost.

A public cloud relies on the provider's security measures and gives less control, while a private cloud can apply custom security policies with full oversight.

False.

The provider manages security, but the organisation is still responsible for protecting user data and for how personal data is stored.

A wired network is a network where physical cables are used to join devices together and transmit data.

A wireless network is a network where connections are made using radio waves to transmit data through the air.

Speed, with fast data transfer; security, with better physical security; and range, which is high at up to 100 m and less susceptible to interference.

Poor portability, since location is limited by the physical cable; cost, since more cables are needed to add a device; and safety, since cables can be trip hazards needing routing along walls or under floors.

Portability, since location is only limited by range; cost, since it is less expensive to set up and add devices; and compatibility, since most devices have a built-in wireless adapter.

Speed, which is slower than wired; security, which is weaker than wired; and range, which relies on signal strength to the WAP and can be obstructed.

Transmission media is the type of cable used in wired connections.

Twisted pair, coaxial and fibre-optic.

It carries electrical signals between devices on a local area network, and is common in offices and homes connecting desktop computers and servers.

It has a slower transfer rate than coaxial and fibre-optic, and it can suffer from external electromagnetic interference.

It was used in telecommunication to transmit voice signals, forming the traditional landline phone network, and was adapted to deliver network traffic on a WAN, making the internet possible.

Fibre optic uses light to transmit data on a wide area network.

It transmits at high speed with higher bandwidth, it does not suffer from interference so is the most secure option for sensitive data, and it can cover long distances without degradation.

Twisted pair is cheap, coaxial is medium cost, and fibre optic is expensive.

False.

Wired connections offer a higher bandwidth than wireless connections.

A hub is a 'dumb' device that passes on anything received on one connection to all other connections, broadcasting it to every device on the network.

It creates unnecessary traffic, especially with a large number of devices, and it raises a security concern because every device receives the data packet.

A switch uses packet switching and only sends data to the device it was intended for, which improves network efficiency.

A switch decides where to send a packet using its lookup table.

It examines the destination MAC address, looks that address up in its lookup table, and forwards the packet to the corresponding port.

A server is a powerful computer that provides services or resources to other devices on a network, called clients — it can manage and store files, host websites, control access to printers, or run applications.

Because of their importance and high uptime requirements — they are designed to handle multiple requests at once and stay on 24/7.

To send and receive data packets between the computer and the network, converting the computer's data into a network-friendly format.

A MAC address, used to identify the device on the network.

A WNIC uses radio waves to send and receive data to a wireless router or access point, converting the device's data into a wireless signal rather than using a cable.

It allows wireless devices to connect to a wired network, acting like a bridge between the wired and wireless parts of a network and extending the range of the wireless network.

It connects two separate network segments together, often joining two LANs so they act as one larger network, and can filter traffic by checking MAC addresses.

It boosts or regenerates signals, receiving a weak signal and retransmitting it at full strength so data can travel long distances without losing quality.

A router routes data from a local area network to another network connection, joining two networks together by analysing data packets and determining the best path to the destination.

The header contains information about the packet, including the IP address of the sender and intended recipient, while the payload is the actual data being sent.

It analyses the packet header to determine the destination IP address, looks that IP address up in a routing table to determine the next network, and forwards the packet to the appropriate network or device.

A hop.

False.

It has a public IP address assigned by an Internet Service Provider, and other routers use that public address to identify and direct packets to the network.

Wiring, data transmission and data encapsulation.

Ethernet is a wired networking standard used in local area networks, and data is transmitted in frames.

It is a sequence of bits used to synchronise communication between devices.

The destination MAC address, the unique ID of the device the data is being sent to, and the source MAC address, the unique ID of the sending device.

The type of data or the size of the payload.

The Frame Check Sequence in an Ethernet frame is used for error detection.

Carrier Sense Multiple Access with Collision Detection.

It checks whether the channel is free — if the channel is busy the device waits, and if it is free the device transmits.

Because all devices share the same cable, two can start to send data at the same time, causing a collision.

A jamming signal.

Both stop transmitting, and each waits for a random amount of time before trying again.

A bus topology.

False.

Each device waits a random amount of time before attempting to resend, which is what stops the collision repeating.

Bit streaming is the continuous flow of data (bits) sent over the internet or a network.

So that it can be played back immediately, reducing the need to download the entire file before use.

Real-time and on-demand.

Real-time content is streamed and watched at the same time, while with on-demand you choose when to watch.

Live sports, live news, online gaming and video calls.

It needs low delay to feel live, whereas on-demand can handle small delays thanks to buffering.

Real-time events usually have no pause or rewind, while on-demand lets the viewer pause, rewind or skip.

Bit rate is the amount of data able to be transmitted in a specified unit of time, usually seconds.

Bit rate and broadband speeds.

It allows higher quality content with sharper, clearer images and sound, but uses more network bandwidth and may require a larger buffer.

Quality is lower, with more pixelation or blurriness, especially during fast movement.

Streaming platforms will adjust bit rates based on network performance.

False.

Slow broadband causes frequent buffering and interruptions as well as pixelation and lower sound quality, and struggles with live or interactive services.

The Internet is a global network of networks, the most well-known wide area network, providing the infrastructure used to give connectivity to the World Wide Web.

The World Wide Web is a collection of websites and web pages that are accessed using the Internet, consisting of interconnected documents and multimedia files stored on web servers.

The Internet uses protocols like TCP/IP to transfer data between devices and networks, while the Web uses HTTP and HTTPS to request and deliver web content.

Tim Berners-Lee, in 1989, envisioning it as a way to share and access information on a global scale.

Modulator-demodulator — it converts digital signals from a computer into analogue signals to send over telephone or cable lines, and converts analogue back into digital so the computer can understand them.

Public Switched Telephone Network — it was originally built to handle voice communication over copper wires.

It was adapted to enable internet access, and is used to connect computers, devices and LANs between towns and cities.

Traditional copper telephone lines are slowly being replaced with fibre optic cables.

Fibre gives access to higher bandwidth and faster data transfer speeds.

A dedicated line provides an exclusive, high-speed connection between two points that is always active and not shared with other users, making it faster and more reliable.

A T1 line reaches up to 1.54 Mbps, a T3 line up to 45 Mbps, and fibre-optic reaches speeds in the gigabits.

Video conferencing, cloud computing and large file transfers, for businesses and organisations needing consistent high bandwidth.

It is made up of cells, each served by a cell tower or base station, and devices connect to the nearest tower to send and receive signals.

As a user moves, their device automatically switches to the next closest tower.

False.

The Internet is the infrastructure, a global network of networks; the World Wide Web is the collection of websites and web pages accessed using it.

An IP address is a unique identifier given to devices which communicate over the Internet, making it possible to deliver data to the right device.

IP addresses are dynamic, so the IP address will change.

Four blocks of denary numbers between 0 and 255, separated by full stops, with each block 1 byte and the whole address 4 bytes or 32 bits.

Eight blocks of 4 hexadecimal digits, separated by colons, with each block 2 bytes and the whole address 16 bytes or 128 bits.

The first instance of multiple groups of zero can be replaced by a double colon.

IPv4 provides just over 4 billion unique addresses, which is not enough for over 7 billion people with countless devices each.

Subnetting is the process of dividing a larger network into smaller, more manageable parts called subnets, each working like a mini-network within the main network.

It reduces network traffic, improves speed and performance by keeping data in its local subnet, increases security by limiting access, is easier to manage and maintain, and improves organisation by grouping devices by department or function.

Larger networks, such as schools or businesses, to reduce traffic, keep data local and make management easier.

Devices that need a constant connection to the internet, such as web servers and email servers.

A public IP address is globally unique — no two devices can share one.

A router assigns it to devices on a local area network, and because private addresses are not routable on the internet, devices are not exposed to the public internet.

A static IP address is a fixed IP address that does not change, assigned to devices that need a consistent address.

Websites, remote access services, and email or file servers.

A dynamic IP address is temporarily assigned when a device connects to the network, taken from a pool of available IP addresses.

A DHCP server, which stands for Dynamic Host Configuration Protocol.

False.

Laptops, smartphones and guest devices are ideal for dynamic addresses, because a fixed address is not needed.

A Uniform Resource Locator is a unique identifier for a web page, known as the website address, and is text-based to make it easier to remember.

The protocol, the domain name and the web page or file name.

The communication method used to transfer data between client and server.

The name of the server where the resource is located.

The location of the file or resource on the server.

The DNS translates domain names into IP addresses, so users do not have to remember the IP address of every website they visit.

Its own cache, to see if it already knows the IP address for the website.

A DNS server stores an index of domain names and their matching IP addresses.

It passes the request on to a higher-level DNS server.

It points to the correct Top-Level Domain (TLD) server, which in turn points to the authoritative DNS server for that domain.

It responds with the correct IP address for the domain.

The browser sends a request to the web server at that IP address, the server processes the request and sends back the website's data, and the browser renders the content and displays it.

DNS propagation is the updating of the DNS when a domain is registered or its server IP address changes, which may take some time to spread across the internet.

False.

Computers use IP addresses to find and connect to servers; the DNS exists to translate the domain name into that IP address.