5 - Networks Flashcards
https://studyrocket.co.uk/revision/gcse-computer-science-aqa/written-assessment/network-protocols
What is a computer network?
2 or more computers connected to each other by wired/wireless connections to allow communication
What are some advantages of computer networks?
-sharing data is easier + faster
-shared peripheral hardware (printers)
-central management of security/updates/backups
What are the disadvantages of computer networks?
-security issues (malware can spread faster)
-cost of setup + maintenance
-if server fails the whole network fails
Describe the main types of networks:
-LAN (local area), small geographical area, managed by a single person/organisation
-WAN (wide area), large geographical area (eg the Internet), collective/distributed ownership, and it usually uses encryption
-PAN (personal area), used for temporary data transmission among very localised devices with Bluetooth
How can you connect a network?
-wired (twisted pair copper cable, fibre optics for higher bandwidth)
(coaxial too, but not used in networks as much now)
-wireless (Wi-Fi, Bluetooth)
LANs that use Wi-Fi are called a Wireless LAN (WLAN)
Why might a wireless network be worse than a wired one?
-sent by radio waves, which can be subject to interference (due to obstructions/other devices)
-susceptible to interception attacks from hackers
-slower (less bandwidth)
Give 3 advantages of wireless networks in comparison to wired networks:
-flexibility of expanding network to other users
-no need for drilling holes/installing cabling
-mobility of users and devices
What is a network topology? Describe the main types of LAN topology:
A given arrangement of all the elements you need for networking
bus:
-devices connected along one main backbone with 2 terminators at either end
star:
-devices connected to a central switch
The terminators stop signals being reflected back down the cable and causing interference
Pros and cons of a bus topology:
-cheap (less cabling)
-not dependent on a central switch
-if backbone is broken, network is all broken
-less secure, every computer sees the data being transferred
-doesn’t perform well under large amounts of traffic (frequent collisions of data)
Pros of a star topology:
-secure, data only travels to the necessary device
-break in cable means only the device which it connected to will disconnect
-performs well under heavy traffic (no collisions)
-multiple computers can connect to server at once
What are the downsides of using a star topology?
-if switch breaks, the entire network fails
-expensive (more cabling)
The first point is actually a valid answer in most cases surprisingly
What is a node?
A device on a network
What is a network protocol?
a set of rules that allow 2 devices on a network to communicate in some way
Describe the ethernet protocols:
standard set of protocols used on wired networks
Describe the Wi-Fi protocols:
trademark + standard set of protocols, used for wireless data transmission on WLANs
Wireless LANs
What is TCP, and what does it do?
-Transmission Control Protocol splits data into packets and rejoins them
-ensures packets arrive at the destination to provide error free transmission across a network
-connects users to the Internet
It uses acknowledgement messages from the receiving device, which tells the sending device which packets have been received
What is IP and what is it responsible for?
-Internet Protocol is responsible for packet switching, by defining the start and destination address of each packet, so that it gets routed to the correct place
-it relays data across network boundaries
Packet switching just means routing packets across a network
What do TCP and IP make up together?
-TCP/IP model (with 4 layers)
-controls communication over the Internet
Also known as the TCP/IP stack
What is UDP and how is it different to TCP?
User Datagram Protocol has a similar function to TCP but has no error checking, for lower latency
What is UDP used for?
-used for sending short messages with datagrams where speed is more important than accuracy (ideal for online gaming, lower latency)
-now obsolete as it is less reliable than TCP
What is HTTP and what does it allow the client to do?
-Hypertext Transfer Protocol
-allows the client to send requests for HTML web pages (to the server)
What is HTTPS, and how does it differ from HTTP?
-secure version of HTTP
-has encryption and authentication protocol alongside it
What is FTP and what is it used for?
-File Transfer Protocol
-allows for secure transfer of files between a client and server
How is FTP usually used?
-FTP clients which are software programs that sit on top of the actual protocol
-interacting with the program generates and sends the appropriate FTP commands
What is SMTP and what is it used for?
-simple mail transfer protocol
-used to send emails from a client machine to an email server
Between email servers, TCP/IP stack is used
What is IMAP and what does it control?
-internet message access protocol
-controls download/upload of emails to and from a mail server
How does IMAP allow for emails to be viewed from other devices?
retrieves the email on the device being used, but also leaves a copy on the mail server so it can be viewed on other devices
this process is known as “store and forward”
Name the 5 types of protocols in order:
-transmission (TCP, UDP)
-addressing (IP)
-connection (Wi-Fi/ethernet)
-email (SMTP, IMAP)
-transfer (HTTP(S), FTP)
(TACET)
Why do we need network security?
-keep sensitive data safe from cyber attacks
-ensures that the network is usable and can be trusted
What are the 4 ways of managing a network’s security? How can they be improved?
-authentication
-encryption (turns info into unreadable data, only decrypted with a key)
-MAC address filtering
-firewall
-when used in combinations it provides a network with a greater level of security
What does MAC address filtering do?
MAC address filtering allows/blocks devices from accessing a network based on the physical media access control address embedded within the device’s network adapter
What is authentication? Give some ways a user can be authenticated:
-methods to make sure a user is who they say they are, so that they are only allowed access if they match stored information about them, and then they are given corresponding access rights on the network
-credentials, biometrics, 2FA
What does a firewall do? What doesn’t it do?
-software that monitors incoming/outgoing network traffic to see if any packets are malicious
-controls whether to allow/block certain packets based on a defined set of security rules
-they do not prevent virus attacks
What are the 4 layers involved in the TCP/IP model?
-application
-transport
-internet
-link (network access/interface layer)
(ATIL)
Why is the TCP/IP model split into layers?
-decomposes complex task of networking into smaller/simpler tasks, where each layer handles a different part of the communication
-easier to fix certain layers without affecting the others
What happens at the application layer, and what types of protocols are used?
-network applications (web browsers/email programs) operate here
-transfer and email protocols
What happens at the transport layer, and what types of protocols are used?
-sets up the communication between the two hosts and agrees settings (eg language, packet size)
-transmission protocols
What happens at the internet/network layer, and what types of protocols are used?
-addresses (adds IP to) packets for transmission
-addressing (IP) protocols
Internet layer is also known as the network layer
What happens at the link layer, and what soft/hardware are found here?
-data sent over the network by wired/wireless connections
-network hardware (eg NIC) and OS device drivers are found here
The drivers allow the OS to communicate with certain devices
What are routers responsible for?
transmitting data between devices on a network
What is the role of the server?
store/retrieve/send data on a network
What is a packet of data, and what is sent along with it?
-a block of data to be transferred over a packet-switching network
-contains information like its start/destination IP address
How is packet switching used to send data across a network?
-sending device splits data into numbered packets with destination address
-directed across network between routers across a path determined by current network traffic
-at destination, packets are ordered to check if none are missing/corrupt
-sends acknowledgement message to tell receiving device which packets were received, so packet loss can be identified
This error checking is only used for TCP, and not UDP
What is the bandwidth of a network?
the maximum rate of data transfer across a network
Why might only using usernames and passwords be less secure in an authentication system?
-susceptible to shouldering
-user might not choose a strong password, can be cracked easily
-difficult to verify actual identity of the person logging in (compared to biometrics/2FA)
