5 - Networks

Question 1

What is a computer network?

Answer 1

2 or more computers connected to each other by wired/wireless connections to allow communication

Question 2

What are some advantages of computer networks?

Answer 2

-sharing data is easier + faster
-shared peripheral hardware (printers)
-central management of security/updates/backups

Question 3

What are the disadvantages of computer networks?

Answer 3

-security issues (malware can spread faster)
-cost of setup + maintenance
-if server fails the whole network fails

Question 4

Describe the main types of networks:

Answer 4

-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

Question 5

How can you connect a network?

Answer 5

-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)

Question 6

Why might a wireless network be worse than a wired one?

Answer 6

-sent by radio waves, which can be subject to interference (due to obstructions/other devices)
-susceptible to interception attacks from hackers
-slower (less bandwidth)

Question 7

Give 3 advantages of wireless networks in comparison to wired networks:

Answer 7

-flexibility of expanding network to other users
-no need for drilling holes/installing cabling
-mobility of users and devices

Question 8

What is a network topology? Describe the main types of LAN topology:

Answer 8

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

Question 9

Pros and cons of a bus topology:

Answer 9

-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)

Question 10

Pros of a star topology:

Answer 10

-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

Question 11

What are the downsides of using a star topology?

Answer 11

-if switch breaks, the entire network fails
-expensive (more cabling)

The first point is actually a valid answer in most cases surprisingly

Question 12

What is a node?

Answer 12

A device on a network

Question 13

What is a network protocol?

Answer 13

a set of rules that allow 2 devices on a network to communicate in some way

Question 14

Describe the ethernet protocols:

Answer 14

standard set of protocols used on wired networks

Question 15

Describe the Wi-Fi protocols:

Answer 15

trademark + standard set of protocols, used for wireless data transmission on WLANs

Wireless LANs

Question 16

What is TCP, and what does it do?

Answer 16

-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

Question 17

What is IP and what is it responsible for?

Answer 17

-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

Question 18

What do TCP and IP make up together?

Answer 18

-TCP/IP model (with 4 layers)
-controls communication over the Internet

Also known as the TCP/IP stack

Question 19

What is UDP and how is it different to TCP?

Answer 19

User Datagram Protocol has a similar function to TCP but has no error checking, for lower latency

Question 20

What is UDP used for?

Answer 20

-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

Question 21

What is HTTP and what does it allow the client to do?

Answer 21

-Hypertext Transfer Protocol
-allows the client to send requests for HTML web pages (to the server)

Question 22

What is HTTPS, and how does it differ from HTTP?

Answer 22

-secure version of HTTP
-has encryption and authentication protocol alongside it

Question 23

What is FTP and what is it used for?

Answer 23

-File Transfer Protocol
-allows for secure transfer of files between a client and server

Question 24

How is FTP usually used?

Answer 24

-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

Question 25

What is SMTP and what is it used for?

Answer 25

-simple mail transfer protocol -used to send emails from a client machine to an email server ## Footnote Between email servers, TCP/IP stack is used

Question 26

What is IMAP and what does it control?

Answer 26

-internet message access protocol -controls download/upload of emails to and from a mail server

Question 27

How does IMAP allow for emails to be viewed from other devices?

Answer 27

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 ## Footnote this process is known as "store and forward"

Question 28

Name the 5 types of protocols in order:

Answer 28

-transmission (TCP, UDP) -addressing (IP) -connection (Wi-Fi/ethernet) -email (SMTP, IMAP) -transfer (HTTP(S), FTP) (TACET)

Question 29

Why do we need network security?

Answer 29

-keep sensitive data safe from cyber attacks -ensures that the network is usable and can be trusted

Question 30

What are the 4 ways of managing a network's security? How can they be improved?

Answer 30

-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

Question 31

What does MAC address filtering do?

Answer 31

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

Question 32

What is authentication? Give some ways a user can be authenticated:

Answer 32

-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

Question 33

What does a firewall do? What *doesn't* it do?

Answer 33

-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**

Question 34

What are the 4 layers involved in the TCP/IP model?

Answer 34

-application -transport -internet -link (network access/interface layer) (ATIL)

Question 35

Why is the TCP/IP model split into layers?

Answer 35

-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

Question 36

What happens at the application layer, and what types of protocols are used?

Answer 36

-network applications (web browsers/email programs) operate here -transfer and email protocols

Question 37

What happens at the transport layer, and what types of protocols are used?

Answer 37

-sets up the communication between the two hosts and agrees settings (eg language, packet size) -transmission protocols

Question 38

What happens at the internet/network layer, and what types of protocols are used?

Answer 38

-addresses (adds IP to) packets for transmission -addressing (IP) protocols ## Footnote Internet layer is also known as the network layer

Question 39

What happens at the link layer, and what soft/hardware are found here?

Answer 39

-data sent over the network by wired/wireless connections -network hardware (eg NIC) and OS device drivers are found here ##Footnote The drivers allow the OS to communicate with certain devices

Question 40

What are routers responsible for?

Answer 40

transmitting data between devices on a network

Question 41

What is the role of the server?

Answer 41

store/retrieve/send data on a network

Question 42

What is a packet of data, and what is sent along with it?

Answer 42

-a block of data to be transferred over a packet-switching network -contains information like its start/destination IP address

Question 43

How is packet switching used to send data across a network?

Answer 43

-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 ## Footnote This error checking is only used for TCP, and not UDP

Question 44

What is the bandwidth of a network?

Answer 44

the maximum rate of data transfer across a network

Question 45

Why might only using usernames and passwords be less secure in an authentication system?

Answer 45

-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)