Computer Science A-Level > Networks > Flashcards

Networks Flashcards

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1
Q

What is a network?

A
  • A set of interconnected devices designed to share resources, exchange data and communicate with each other
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2
Q

What is the main purpose of a network?

A
  • To enable data and resource sharing, communication, and collaboration between different devices
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3
Q

What is a protocol and what is its purpose?

A
  • Network protocols define the rules and formats that devices must follow to communicate with each other over the network
  • They ensure successful and secure data transmission, and help maintain order and efficiency in communications
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4
Q

What is a standard?

A
  • A standard in a network or any data transfer situation refers to a set of guidelines or frameworks that govern how a task should be performed or how a product should function
  • Standards ensure compatibility and consistency across different devices and software
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5
Q

What is the importance of standards?

A
  • Standards allow different network devices, regardless of their manufacturer or model, to work together seamlessly
  • They ensure that data can be correctly interpreted and processed by the receiving device, regardless of where or how it is sent
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6
Q

What is HTTP?

A
  • Primary protocol for transferring web content (texts, images, videos)
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7
Q

What is HTTPS?

A
  • A version of HTTP, but with encryption for security
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8
Q

What is SMTP?

A
  • The standard for sending email messages between servers or from a client to a server
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9
Q

What is FTP?

A
  • Used for transferring files from one host to another over a network
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10
Q

What is ARP?

A
  • Translates IP addresses into MAC addresses
  • This ensures that data packets reach the correct device on a network
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11
Q

What is TCP?

A
  • Part of the main suite of protocols used in the Internet Protocol Suite
  • Provides reliable, ordered and error-checked delivery of a stream of packets
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12
Q

What is UDP?

A
  • A simpler message-based connectionless protocol
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13
Q

What is IP?

A
  • Functions mainly by addressing and routing packets of data from the source to the target device
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14
Q

What is protocol layering?

A
  • Protocol layering is the way network protocols are divided into layers, each of which performs specific functions
  • This allows for modular design and simplifies troubleshooting
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15
Q

What protocols is the internet based on?

A
  • The internet is based on the TCP/IP stack
  • This is a layer of protocols
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16
Q

Why do we use protocol layering?

A
  • Modularity: by breaking the complex process of networking into more manageable layers, it’s easier to design, implement and troubleshoot networks
  • Allows different technologies to work together seamlessly
  • Ease of updates: changes can be made to one layer without affecting others
  • Specialisation: each layer can be specialised to perform a specific function
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17
Q

What is the TCP/IP stack?

A
  • A suite of communication protocols used to interconnect network devices onto the internet
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18
Q

What are the layers of the TCP/IP stack?

A
  • Application
  • Transport
  • Internet
  • Link
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19
Q

What is the application layer in the TCP/IP stack?

A
  • This is the layer where the communication process begins
  • The application layer interacts directly with software applications, such as web browsers and email clients
  • The application layer prepares data for transmission over the network by converting it into a format that can be sent and received over the network (known as encapsulation)
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20
Q

What is the transport layer in the TCP/IP stack?

A
  • The transport layer receives data from the application layer
  • The transport layer is responsible for end-to-end communication between the source and destination
  • The transport layer breaks the data it receives down into smaller units called packets
  • Each packet is assigned a port number (so the data can be reassembled in the correct order at the destination)
  • Each label is also labelled with a header containing information, such as the packet number
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21
Q

What is the internet layer in the TCP/IP stack?

A
  • The internet layer receives packets from the transport layer
  • It adds a header to each packet, including the sender’s IP address and the receiver’s IP address
  • The internet layer is responsible for routing each packet across the network using the IP addresses in the headers
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22
Q

What is the link layer in the TCP/IP stack?

A
  • The link layer receives packets from the internet layer and prepares them for transmission over the physical network
  • The link layer translates the digital packets into an electrical, optical or wireless signal that can be sent over the network
  • Once the signal reaches the receiving end, the network layer translates it back into digital packets
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23
Q

How do the TCP/IP layers work?

A
  • At each layer of the TCP/IP model, specific tasks are performed to prepare data for transmission over the network
  • The process is reversed at the receiving end, with each layer removing its specific header and performing its specific tasks to get the data back into a format that the receiving application can use
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24
Q

What type of network does the internet rely on for data transmission?

A
  • The internet relies on packet-switched networks
  • Here, data is broken down into packets, each of which can take its own route to the destination
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25
What is a packet?
- Units of data - They are small and easier to manage
26
What does a packet contain?
- The payload (the data) - A header (with metadata like source and destination IP address) - A footer (to signify the end of the packet)
27
What is an IP address?
- A unique identifier for a device on a network - IP addresses are used to deliver packets to the correct destination
28
What is the DNS?
- The Domain Name System - A directory of domain names that is used to translate human-readable domain names to the numeric IP addresses that computers use
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What does the DNS do?
- When you type a URL into your browser, the DNS translates the domain name into its associated IP address so your computer can connect to the server hosting the website
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What is DNS propagation?
- When a domain is newly registered, or a server changes its IP address, the DNS for that record needs to be updated - This is known as DNS propagation
31
What are the components of the DNS?
- DNS resolver - Root servers - TLD (Top-Level Domain) servers - Authoritative DNS servers
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What is the DNS resolver?
- The first stop in the DNS lookup process - Usually provided by your Internet Service Provider (ISP)
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What are the root servers?
- The resolver asks a DNS root server to find the Top-Level Domain (like .com or .org)
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What is the TLD server?
- Top-Level Domain servers - The root server directs the resolver to a TLD server - This stores information about the domain
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What are the authoritative DNS servers?
- The TLD server then responds with the IP address of the domain's authoritative DNS server, which the resolver asks for the IP of the domain
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What are the benefits of DNS?
- DNS allows us to use easily remembered domain names instead of hard-to-remember IP addresses - DNS servers handle the mapping between domain names and IP addresses, relieving end users and system administrators from the task
37
What is the DNS lookup process?
- URL entry - The computer checks its local cache to see if it contains the domain's IP address from a previous query - DNS query: the computer sends a query to a DNS server to translate the URL into an IP address - The DNS resolver checks its cache to see if it has the domain's IP address. If not, it sends the request to the DNS root server - Root server query: the root server directs the resolver to the TLD server based on the extension (.com, .org) - TLD server request: the TLD server then provides the resolver with the IP address of the domain's authoritative DNS server - The resolver queries the authoritative DNS server for the IP address of the domain - The IP address is returned from the authoritative DNS server - Web page is requested - Server responds with the data of the webpage, which is then rendered
38
What is a LAN?
- Local Area Network - LANs are networks that are contained within a small geographical location - Typically, all the hardware used to make a LAN is owned by a single entity. This makes them more secure than WANs, which have connections owned by third-party companies
39
What is a LAN built using?
- A LAN is a network that is built using hubs and/or switches that connect several devices - It is common for one hub or switch to be connected to a router, which allows the LAN to connect to other networks, such as the internet
40
What are the advantages of a LAN?
- Centralised management: a LAN allows centralised management of updates, backups and software installation - Security: a LAN can secure its devices with the use of firewalls, antivirus software and other security features - File sharing and collaboration: a LAN allows users on the network to share resources such as printers and other peripherals
41
What are the disadvantages of a LAN?
- If hardware fails, the network may not function properly or at all - Networks are more prone to attacks than standalone computers - Access to data and peripherals can be slow depending on network traffic - LAN networks require maintenance to ensure that software is up to date
42
What is a WAN?
- Wide Area Network - A WAN connects multiple Local Area Networks (LANs) over a large geographical area
43
What are the characteristics of a WAN?
- A WAN allows users in different locations to share data and resources as if they were on the same network - WANs usually use third-party connections - These connections are provided by ISPs or telecommunications companies rather than owned by a single organisation
44
What are the advantages of a WAN?
- Enables communication and data sharing between offices or sites in different locations - Allows access to central servers and shared databases from anywhere with a connection
45
What are the disadvantages of a WAN?
- Typically slower than LANs due to greater transmission distances - More expensive to set up and maintain because of ISP costs - More vulnerable to security risks as data travels across public networks
46
What is packetising?
- Packetising is a process where a large message is divided into smaller, manageable units called packets - Each packet can then be sent individually over the network
47
Why are headers used in packetising?
- Headers contain information necessary for the packet's delivery - Typical information in a header includes: - Source IP address - Destination IP address - Sequence number: used to reassemble packets - Protocol - Packet length - Checksum: a value used for error-checking
48
How are packets transmitted over a network?
- After being packetised and encapsulated with headers and footers, packets are transmitted individually across the network - Packets might take different routes to reach their destination
49
What happens when all the packets have reached the destination?
- They are reassembled back into the original message using information in the headers
50
What is packet switching?
- Packet switching is a networking communication method that breaks down data (large files, emails) into smaller packets - It sends these packets separately along different routes, and then reassembles them at their destination
51
What is circuit switching?
- Circuit switching is a communication method where a dedicated communication path is established between two devices for the duration of their conversation, and all packets are sent along the same route
52
What are the benefits of packet switching?
- Efficient use of network resources as packets can follow different paths to the destination, using more of the available bandwidth - More reliable, as if a single packet fails to reach its destination, only that packet needs to be resent, not the entire data stream - Lower cost due to shared network resources
53
What are the drawbacks of packet switching?
- Not ideal for real-time services like video calling, which require a steady stream of data without delays - Packets can arrive out of order, requiring reassembly and error-checking - Potential for congestion in the network
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What are the benefits of circuit switching?
- Ideal for real-time services with a constant data transmission rate - No delays as a dedicated path is established - Data arrives in order as it follows the same path
55
What are the drawbacks of circuit switching?
- Less efficient, as resources remain allocated during the whole conversation, even when no data is being sent - It is more costly due to the dedicated line requirement - Less flexible and scalable, as adding new devices can be complex
56
What are common network threats?
- Hackers - Viruses and malware - Denial of Service (DoS) - SQL injection - Phishing - Pharming - Social engineering
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What are hackers?
- Individuals or groups who exploit system vulnerabilities to gain unauthorised access to data - Involves gaining unauthorised access to a system or network to steal or manipulate data, disrupt services, or cause damage
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What are viruses?
- Malicious software programs designed to spread from one computer to another and interfere with normal operations - A virus attaches itself to a legitimate file and then replicates itself to spread to other programs or files on the computer
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What is malware?
- Malware is malicious software designed to harm or gain unauthorised access to a system or network
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What are the different types of malware?
- Worm: similar to a virus, but is a standalone program that can spread and replicate itself over computer networks - Trojan horse: a program that disguises itself as a legitimate program or file - Spyware: software that records all key presses and transmits them to a third-party - Adware: software that displays unwanted advertisements without the user's consent Ransomware: software that encrypts a user's files and demands a ransom payment to decrypt them
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What is Denial of Service (DoS)?
- A DoS attack is where a computer floods a server with lots of requests at the same time, which the server can't respond to, causing it to crash or become unavailable to users - A DoS attack aims to disrupt the normal functioning of a system or network by denying users access
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What is a Distributed Denial of Service attack (DDoS)?
- Similar to a DoS attack - Multiple computers are used as bots, which send the requests to the server
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What is SQL injection?
- An attack technique used to exploit security vulnerabilities in a website, where malicious SQL statements are inserted into an entry field for execution - This can potentially expose a company's database to hackers
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What is phishing?
- Attempting to acquire sensitive information by masquerading as a trustworthy entity in an electronic communication - Phishing involves the user being sent an email that looks legitimate - The email contains a link to a fake website where the user is encouraged to enter their details - Phishing aims to steal sensitive information for personal gain or to use for further cyber attacks
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What is pharming?
- This is a cyber attack intended to redirect a website's traffic to another bogus site - Pharming involves malware being downloaded without the user's knowledge - This redirects the user to a fake website where they're encouraged to enter their personal details
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What is social engineering?
- Social engineering involves manipulating individuals to gain access to confidential information or to perform an action that benefits the attacker
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What are some methods of social engineering?
- Enticing a victim with the promise of a desirable item to extract sensitive information - Posing as a bank representative and asking for personal information - Posing as a colleague to gain trust and access to sensitive information
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What are some methods of network security?
- Firewall - 2FA - Secure passwords - Anti-virus / anti-spyware software - Regular software updates
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What is a firewall?
- Network security systems that monitor and control incoming and outgoing network traffic based on predetermined security rules
70
What hardware is needed in a network?
- Modem - Router - Cables - NIC (Network Interface Card) - Wireless Access Point (WAP) - Hub - Switch
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What is a modem?
- A device that modulates an analogue carrier signal to encode digital information and also demodulates a carrier signal to decode transmitted information - It enables a computer to transmit data over telephone or cable lines by converting digital signals into analogue and vice versa for receiving data
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What is a router?
- A router is a device that routes data from a LAN to another network connection - it joins two networks together - Routers analyse data packets and determine the best path for the packet to reach its destination
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What does a router do?
- A router used to connect a LAN to a WAN will have a public IP address, which has been assigned to it by an ISP - It is this public IP address that other routers use to identify and direct packets to the network
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How does a router work?
- A router receives incoming data packets from one network and analyses the packet header to determine the destination IP address - It then looks up the IP address in a routing table (of known networks) to determine the next network where the packet should be sent - The router then forwards the packet to the appropriate network or device - This process is repeated until the data packet reaches its destination
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What other functions does the router carry out?
- Assigning IP addresses to devices within the LAN - Filtering incoming traffic based on certain criteria
76
What do cables do in a network?
- Cables are the physical path for data to travel between devices in a network - Ethernet cables are a common type of network cable used for wired networks - Fibre-optic cables use light to transmit data, offering much higher speed and larger data capacity
77
What is a NIC?
- Network Interface Card - A hardware component that enables a device to connect to a network - Have built-in Ethernet ports, meaning they can be connected via cables - It provides a dedicated, full-time connection to a network
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What is the primary function of an NIC?
- Every NIC has a unique identifier called a MAC address, used to identify the device on the network - The primary function of the NIC is to send and receive data packets between the computer and the network
79
What is a WAP?
- Wireless Access Point - Act as a central transmitter and receiver of WiFi signals - WAPs connect to the wired network from a fixed location using cables and project a WiFi signal to a designated area - In a large network, multiple WAPs are used to provide extensive coverage and handle many connections
80
What is a hub?
- A hub is a networking device which is used to connect multiple devices in a network - Hubs are "dumb" devices: they pass on anything received on one connection to all other connections - This can lead to network inefficiencies and security issues
81
Why are hubs cheaper than switches?
- When a hub receives a data packet, it will broadcast it to every device on the network - This creates unnecessary traffic and security concerns
82
What is a switch?
- A networking device that connects devices on a network and uses packet switching to receive, process and forward data to the destination - Unlike a hub, a switch only sends data to the device it was intended for
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What is the difference between a hub and a switch?
- A switch is more expensive - This is because hubs transmit data to all devices on the network, while switches only forward data to the intended device - This improves security and efficiency by reducing traffic
84
How does a switch work?
- It uses a lookup table to transmit data to the correct device - When a switch receives a data packet, it examines the destination MAC address and looks up the address in the lookup table - It will then forward the packet to the corresponding port
85
What is a client-server network?
- Powerful and reliable "server" computers control the network and "serve" the client with services such as files, emails and web access - Clients connect to the servers to access network services - In this setup, the server hosts, delivers and manages most of the resources and services to be consumed by the clients
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Benefits of a client-server network
- Easier central management - Scalability: new clients can easily be added - Higher reliability as resources are managed centrally
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Drawbacks of a client-server network
- Single point of failure: if the server goes down, services could be unavailable - It can be expensive to set up and maintain - often needs dedicated teams of people to maintain them
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Where are client-server networks usually used?
- Larger organisations where centralised control is needed, and reliability and security are crucial
89
What is a peer-to-peer network?
- This is the simplest type of network - In this setup, all computers in the network share equal responsibility, and there is no central server - All machines have equal status - Data is often spread around the network, with each user being responsible for their data
90
Benefits of a peer-to-peer network
- Easy to set up and less expensive than client-server as no administrative staff are needed - No dependency on central server - Data can be shared directly between systems without the need for a central server
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Drawbacks of a peer-to-peer network
- Lack of central control can lead to security issues and vulnerability - Not suitable for large networks, as it can have performance issues
92
Where are peer-to-peer networks usually used?
- Home networks, small businesses, or for specific applications like file sharing
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