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A Level Comp Sci Paper 1 > 1.3.3 Networks > Flashcards

1.3.3 Networks Flashcards

1
Q

What is a network

A

Collection of interconnected computers (2 or more) that can communicate with each other and are connected by either cables or wireless.

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2
Q

What are the different network sizes

A
  • Small businesses with a handful of devices
  • Large corporate networks with thousands of devices
  • Largest network - the internet
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3
Q

What are the advantages of a network

A
  • Users can share files
  • Users can share peripherals and connections to other networks (internet)
  • Users can access files from any other device
  • Servers can control security, software updates and backups for all devices
  • Enable collaboration through tools and shared resources.
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4
Q

What are the disadvantages of networks

A
  • Increased security risks to data.
  • Malware and viruses can spread easily between computers
  • If the server fails, the computers connected may not work
  • Computers may run slower if there is a lot of data travelling on the network.
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5
Q

What are standards

A
  • Are a set of hardware and software specifications that allow manufacturers to create products and services that are compatible with each other
  • Ensures smooth compatibility with devices
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6
Q

Why do we need standards

A
  • Without standards most devices wouldn’t be able to interact or communicate with eachother - are incompatible
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7
Q

Name an example of standards in use

A
  • HTML is an early standard adopted within the World Wide Web for the display of web pages
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8
Q

Exam Question: Head of design tech: Explain why it would be more beneficial to both students and teachers if theses computers were networked

A
  • Students can create their designs on 1 computer and easily open work on machine that is connected to CAM - no memory sticks
  • Printer can queue jobs so students don’t have to wait
  • Can share files collaboratively
  • Teacher can back up students work
  • Added security - behind login wall
  • Network administrator can deploy CAD software to all machines and maintain them.
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9
Q

What is a protocol?

A

Protocols are a set of standard communication rules - allows devices in a network to communicate

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10
Q

What is handshaking?

A
  • Both devices agree on a set of protocols to use.
  • Handshaking signal is sent from 1 device to the other. Must agree to a bit rate, error correction and format of the packet
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11
Q

What are the different physical aspects that need to be considered before a choice of protocol is made

A
  • Wired or wireless
  • Serial or parallel data transmission
  • Synchronous/asynchronous
  • Copper/Fibre optic
  • Simplex, half duplex or full duplex mode.
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12
Q

What are the different logical aspects that need to be considered before a choice of protocol is made

A
  • Bit rate
  • Error detection
  • Packet size
  • Ordering of packets
  • Routing
  • Compression and Encryption
  • Digital signatures
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13
Q

What is HTTP

A

Hypertext Transfer Protocol

  • Allows web pages, including text and images to be transmitted over a network.
  • Way for a client and server to send and receive requests and deliver HTML pages
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14
Q

What is HTTPS

A
  • Hypertext Transfer Protocol Secure
  • Secure version of HTTP - before communications start, data stream is encrypted.
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15
Q

How does HTTPS use SSL and what is the process

A
  • The user makes a request and the server sends the public key
  • Browser checks public key against certificate for that site
  • If the key matches the user sends its own public key to the server
  • A server generates a number using the user’s public key and separately using the public key from the certificate. Sent back to the user
  • User then decrypts both messages using the private key and the public key from the certificate. If the decrypted numbers match, a secure connection will be established
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16
Q

What is FTP and what is its purpose

A

File Transfer Protocol

  • Used for transmitting data between server and client or between computers
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17
Q

What is TCP and what is its purpose

A
  • Transmission Control Protocol
  • TCP provides reliable and error-checked streams of packets over a network.
  • Each packet contains a checksum, sequence number, port numbers.
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18
Q

What is UDP and what is its purpose

A
  • User Datagram Protocol
  • Provides an unreliable communication - no error checking, ordering of packets
  • However makes better use of bandwidth, used to send short messages where speed is more important than accuracy.
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19
Q

What is the purpose of POP and what is it

A
  • Post Office Protocol
  • Retrieves emails from a mail server and transfers them to your device, deleting them from the server in the process.
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20
Q

What is the purpose of IMAP and what is it

A
  • Internet Message Access Protocol
  • Retrieves emails from a server and keeps it on the mail server, maintaining synchronity between devices
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21
Q

What is the purpose of SMTP and what is it

A
  • Simple Mail Transfer Protocol
  • Transfers/Sends outgoing emails between servers and email clients.
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22
Q

What is the Internet

A
  • The internet is the most well known wide area network (WAN)
  • Nothing more than a collection of interconnected networks, satellites, routers, cables
  • World Wide Web is a service on the internet
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23
Q

What is the ISP

A
  • Internet Service Provider
  • Connected to router via a connection
  • ISP is connected to the DNS.
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24
Q

What are routers connected to

A
  • ISP
  • Devices on their own LANs
  • Other routers on the WAN
  • Servers
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25
Q

How is networking complex?

A
  • Encryption, security and authentication of users and data.
  • Different applications for different tasks
  • Splitting data into packets and sequencing packets
  • Different cables.
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26
Q

What is the purpose of layers?

A
  • Is to divide the complex task of networking into smaller, simpler tasks that work together.
  • Hardware/software at each layer has a defined responsibility - provides service to the layer above.
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27
Q

What are the advantages of layers

A
  • Reducing a complex problem into smaller sub-problems
  • Devices can be manufactured to operate at a particular layer
  • Products from different vendors will work together.
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28
Q

What is the TCP/IP stack

A
    • Stands for “Transmission Control Protocol / Internet Protocol”… (1)
    • Protocol(s)/set of rules… (1) -
  • …for communicating across a network / the internet. (1)
    • Each protocol belongs to a different layer. (1) - The layers are: Application, Transport, Internet, Link (1) -
  • (Starting at the Application layer) data is further encapsulated as it as it is passed to the next layer. (1)
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29
Q

What are the 4 layers in the TCP/IP stack

A
  • Application
  • Transport
  • Internet
  • Link
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30
Q

What is the application layer

A
  • Contains the most protocols which provide a wide range of network services.
  • Provides a protocol relating to the application being sent.
  • Network applications such as web browsers, email programs
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31
Q

What are examples of protocols operating on the application layer

A
  • FTP, HTTP, HTTPS, SMTP, IMAP.
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32
Q

What is the Transport Layer

A
  • Focuses how packets will be transported without looking at the route
  • Responsible for establishing an end-to-end connection and maintaining conversations between application processors
  • Once connection is made, transport layer splits the data into packets.
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33
Q

What is added to each packet (Transport Layer)

A
  • Its number sequence
  • The total number of packets
  • Port number the packet should use/ chescksum
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34
Q

What are examples of Transport Layer Protocols

A
  • TCP, UDP
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35
Q

What is the Internet/Network Layer

A
  • Addresses and packages data for transmission. Routes packets across the network.
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36
Q

What is the protocol used in the Internet/Network Layer

A

IP

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37
Q

What is the Link Layer

A
  • Represents the actual physical connection between network devices.
  • Responsible for adding the unique MAC address of the source device and destination device.
  • When transmitting data between routers over a WAN, MAC address is changed at each hop on the route.
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38
Q

What are examples of things that operate on the link layer

A
  • Copper twisted pair, fibre optic, Wi-Fi, Ethernet
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39
Q

What are I.P addresses

A
  • For computers to talk to eachother they must have a unique address
  • When data is transmitted over network, IP address of both the sender and reciever are in data packet.
  • Used do it can be routed to the right destination.
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40
Q

Why do we need both a MAC address and IP address

A
  • Communication on a LAN only requires link layer which creates frames using MAC addresses
  • Communication on a WAN needs network and link layer
  • Every device has unique MAC address however hard to store all MAC addresses of all devices. Therefore use MAC for LANs while routers cache some IP addresses.
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41
Q

How is data transmitted between hosts on the same network

A
  • Host may need to broadcast first if MAC address is unknown - ARP protocol does this
  • Traffic passes through the switch, switch examines source and destination address.
  • Modern routers do LAN switching and WAN routing
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42
Q

How is data transmitted between hosts on different networks

A
  • Data will be transmitted via a route
  • The destination MAC will the address of the router
  • When the frame reaches the router, router works out where it needs to be sent.
  • Router sets its own MAC address as the source and the next device as the destination.
  • If there are several routers on the path to the destination the source and destination address will be overwritten
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43
Q

What is the World Wide Web

A
  • Collection of files with information stored in hypertext and other associated files.
  • These servers host files and handle client requests
44
Q

How does the domain name server work

A
  1. First the human readable URL is recieved by a DNS resolver server
  2. The server then queries a DNS root name server
  3. The root server responds with the address of the top-level domain server
  4. The resolver makes a request to the .com TLD server
  5. The TLD server then responds with the I.P address of the domain name server
  6. The recursive resolver sends a query to the domain name server
  7. The IP address is then returned to the resolver from the name server
  8. Finally the DNS resolver responds to the web browser with the IP address
45
Q

What are the different types of network

A
  • LAN (Local Area Network)
  • WAN (Wide Area Network)
46
Q

What is a LAN

A
  • A network that that covers a small geographical area, typically located on a single site
  • All the hardware for a LAN tends to be owned and controlled by the organisation using it
  • Use of hard-wiring / wireless communication
47
Q

How are LANs usually connected

A
  • UTP cable
  • Fibre Optic
  • Wi-Fi
48
Q

What is a WAN

A
  • Wide area Network is any network that covers a large geographical area.
  • When multiple LANs physically located in different areas are connected.
  • The infrastructure that makes a WAN is leased from telecommunication companies who manage it.
  • A WAN often uses third party connections.[1] □ Less secure than a LAN
49
Q

What are WANs typically connected by

A
  • Telephone lines, Fibre Optic cables, Satellite Links
50
Q

Describe what a LAN is and state 2 advantages of a LAN instead of a stand-alone machine

A
  • LAN covers a small geographical area.
  • Use of hard-wiring/ wireless communications. Any machine can be used
  • Sharing of peripherals/ monitoring of workers
51
Q

Why is using LAN more secure than WAN

A
  • Usually owned by 1 organisation and secured
  • All networked devices are likely to be managed by a small group of network administrators - manage access/permissions.
  • Data travelling over a WAN is likely to travel over many different network connections - many different companies - high risk of interception
52
Q

What are the 2 common structures for networks

A
  • Client-server and Peer-to-peer
53
Q

What is a client-server

A
  • Services such as file storage are made available to servers which clients connect to in order to access services.
  • Clients and servers make use of request-response model:
    • Client requests to server and if possible provides resource.
54
Q

What does the server do in a client-server model

A
  • Control access and security for a shared file store
  • Manage access to the internet
  • Manage printing jobs
  • Provide email services
  • Run regular backups
55
Q

What are the advantages for a Client-Server

A
  • Easier to manage security
  • Easier to backup shared data
  • Easier to install software updates to all computers
56
Q

What are the disadvantages for Client-Server

A
  • Can be expensive to set up and maintain
  • Requires IT specialists to maintain
  • The server is a single point of failure
  • User will lose network access if the server fails.
57
Q

When are Client-Servers best suited

A
  • Organisations with large number of computers or situations where many computers need access to the same information
58
Q

What are the features of a peer-to-peer model

A
  • Each computer or peer has the same status as others.
  • Peers serve their own files to eachother
  • Each peer is responsible for its own security and data backup
  • Allows large files to be downloaded without server and can share processing load (distributed processing)
59
Q

Explain why the company might have opted for peer-to-peer

A
  • There isnt reliance on the company’s server and its connections to the internet
  • This means it doesn’t have to invest in hardware and bandwidth and system is more likely to be fault tolerant.
60
Q

What are 2 methods of sending packets across a network

A
  • Circuit Switching
  • Packet Switching
61
Q

What is the key benefit of having multiple routes

A
  • If 1 is down because of traffic, alternative routes can be found.
62
Q

What is Circuit Switching

A
  • A route across the network is set up before and all packets are sent down same route - if broken whole circuit will fail
  • Only lasts until complete transmission
  • Has fixed bandwidth however can be wasted
63
Q

What is Packet Switching

A
  • Allows packets to take independent routes through the network. The router will seek alternatives if 1 is broken
  • Maximises bandwidth and can arrive out of order.
64
Q

What is the difference between Circuit Switching and Packet Switching

A
  • C = Physical path, all packets down same path, P= No physical path, travel independently
  • C = Reserves bandwidth in advance can be wasted, P = No reserving bandwidth, no wastage
65
Q

Exam Question: What is meant by Packet Switching

A
  • Data is split into chunks called packets which have labels including address being sent to and order
  • Each packet is sent to the most convenient route meaning they arrive in different order to which they were sent
  • Once packets arrive to reciever they are ordered.
66
Q

What is the aim of network security

A
  • Only allow authorised users to access what they need
  • Prevent unauthorised access
  • Minimise the potential damage cause by unauthorised access
67
Q

What are the different security threats and issues

A
  • Hackers
  • Malware - virus, spyware
  • Denial-of-service attack
  • SQL Injection
  • Social Engineering - Phishing, pharming
68
Q

What is a hacker

A
  • A hacker is a person who attempts to gain access to a computer system with the intent of damaging data or harming the system
69
Q

What are the different forms of hackers

A
  • Black-hat : Gain access via nefarious means (stealing, causing damage)
  • White-hat : Security experts employed by the company - try find vulnerabilities and fix them
  • Grey-hat : Between the other 2. Arent employed but attempt to find flaws (hobby) but is illegal.
70
Q

What is Malware

A
  • Any computer code written with the intent to frustrate or harm
71
Q

What are the effects of Malware

A
  • Deleting, corrupting or encrypting files
  • Causing computers to crash, reboot or slow down
  • Reducing network speeds
  • Logging keyboards inputs and sending them to hackers
72
Q

What are Viruses and what do they do

A
  • Viruses are pieces of code capable of copying themselves and spreading throughout the system
  • Typically designed to have big effect like corrupting a file, destroying data
73
Q

What is Spyware and what does it do

A
  • Spyware covertly obtains information about a user’s computer activities by transmitting data from their device
  • Used to find personal details : surfing habits, emails, passwords
74
Q

What is a DOS attack

A
  • Denial-of-service attack
  • When an attacker floods a server with useless traffic causing the server to become overloaded
  • Often attack high profile organisations - doesn’t lead to loss of data but cost time and money
75
Q

What is a DDOS

A
  • Distributed Denial-of-service attack
  • Occurs when multiple systems orchestrate a synchronised DOS attack against a single target.
  • Attacked from many locations
76
Q

What is an SQL Injection and what does it do

A
  • Code Injection technique used to attack data-driven applications
  • Designed to exploit vulnerabilities in poorly coded database applications
  • Code entered into input text box and executed by server
77
Q

What is Social Engineering and what are the types

A
  • Several different manipulation techniques that exploit human error with a view to obtain private information.
  • Lure users into exposing data
  • Phishing, Pharming
78
Q

What is Phishing

A
  • Online fraud technique which tricks users into giving personal info like passwords.
  • Disguise themselves as a trustworthy source in an electronic communication
79
Q

What is Pharming

A
  • Another fraud technique
  • Malicious code installed on a PC/server misdirects users to fraudulent websites without tehir knowledge
  • “Phishing without lure”
80
Q

What are the different ways to prevent and minimise threats

A
  • Firewall
  • Secure Password System
  • Up-to-date software, anti-malware
  • Proxies
  • Encryption
81
Q

What is a Firewall

A
  • Is a piece of software or hardware configured that only lets some traffic through
82
Q

What does a Firewall Prevent

A
  • Unauthorised internet traffic from outside a LAN
  • Users in a LAN from accessing parts of the internet prohibited by the company they work for
83
Q

Why does a password reduce security threats

A
  • Prevents unauthorised access to a system
84
Q

What is a proxy and what do they do

A
  • A proxy is a physical device that is placed between a network and a remote source
  • Can handle web page requests. User sends requests to the proxy which will forward it onto the client
  • A proxy ensures no direct, physical connection between a single user and remote source
85
Q

Why do people use proxies

A
  • They allow network administrators to filter and monitor internet traffic easily
  • Prevents users from accessing known sites which contain viruses.
86
Q

What is encryption

A
  • Turning plain text into an unreadable form
  • Encrypted using an algorithm and a unique key
  • Makes stolen data hard to read.
87
Q

Suggest a range of ways the company could secure its network and briefly explain how each method works

A
  • Authentication - require username to log on
  • Proxies- Physical computers placed between network and outside world
  • Firewalls - Software and hardware - allows traffic/not
  • Encryption - Encrypts traffic so can’t be read.
88
Q

What is a Modem

A
  • Transforms digital information from the computer into analogue signals that can be transmitted through wires.
  • Can also translate incoming analogue signals back into digital data that the computer can understand
  • Does this by modulating and demodulating electrical signals sent through cables
  • Has 2 ports: 1 that connects to outside world, other connects to computer or router
89
Q

What is a router

A
  • Routers connect networks to other networks (between devices on a small home network, network and the internet)
  • They determine the best route that a packet should take
  • Routers store information about which networks are connected to its port in a routing table
  • Routers perform routing on IP addresses
90
Q

What are 2 main methods of connecting wires

A
  • Wired and Wireless
91
Q

What are the 3 most popular choices of wires

A
  • Twisted Pair cable
  • Coaxial cable
  • Fibre Optic
92
Q

What is a twisted pair cable made of and what is its properties

A
  • Is made of a pair of insulated copper wires
  • Can be affected by noise from external magnetic fields - more affordable
  • Only provides low bandwidth
93
Q

What is a twisted pair cable commonly used for

A
  • Telephone networks, data networks and cable shielding
94
Q

What is a Coaxial Cable made of and what is its properties

A
  • Made of 4 cylindrical components : solid conductor wire, layer of insulation, a grounding conductor and a layer of exterior insulation
  • Can be affected by noise of external magnetic fields - not as much as twisted pair
  • Provides moderate bandwidth
95
Q

What are Coaxial cable commonly used for

A
  • Used for feedlines that connect radio transmitters and recievers to antennas
  • Computer network connections, digital audio and cable TV
96
Q

What is a Fibre Optic Cable made of and what is its properties

A
  • Made of thin optical fibres bundled together into a single cable.
  • Can be glass/plastic
  • High noise immunity as light rays are unaffected by electrical signals
  • High bandwidth - more expensive
97
Q

What are Fibre Optic Cables commonly used for

A
  • Support long distance connections between cities and countries
  • Data centres and organisations transmitting large volume of data.
98
Q

What does NIC stand for and why is it needed

A
  • Network Interface Card
  • Needs this hardware to connect to a network
99
Q

What does a NIC do

A
  • Responsible for placing packets onto network cables in the form of electronic signals
  • Allows wired and wireless communications between computers on a LAN or larger network
  • NIC is both physical and data link layer/ providing circuitry for physical layer and some data link processes to run on it
100
Q

What is a WIC

A
  • A wireless interface card connects to a wireless access point (WAP)
  • Are needed if the connection is wireless
101
Q

What is a WAP

A
  • Wireless Access Point
  • A device that allows wireless devices to connect to a wired network using Wi-Fi or similar standard.
  • This creates a wireless local area network network. It connects to a wired router/switch via a Ethernet cable and projects a Wi-Fi signal. Used as provides full coverage of business. Interference may affect quality
102
Q

What is the Hub

A
  • Allows more than 1 computer to be interconnected in a network by connecting them into 1 central device
  • Operates on the physical layer. Broadcasts transmissions it recieves to all connected devices.
  • Works well for small networks with low network traffic - can be flooded with unneccessary traffic
103
Q

What is the switch

A
  • Rather than repeating the network signals out of all ports, the switch learns the MAC addresses of all devices connected to it
  • It is active compared to the hub which is passive. Routes packets to the right device
    *
104
Q

What is bandwidth

A
  • Measure of how much data can be fitted into a cable at any time
  • High bandwidth means there is more room for data. Data still flows at the same speed
105
Q

Exam Question: Explain why protocols are important in a network

A
  • Allowing them to communicate -
  • By ensuring all devices follow the same rules/standards -
  • So they interpret data/signals in the same way

A Level Comp Sci Paper 1 (16 decks)

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