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A Level Computer Science > 133-networks > Flashcards

133-networks Flashcards

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1
Q

Stand alone machine

A

single computer
not connected to anything

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2
Q

network

A

2 or more computers
connected with
cables/wireless signal
for data transmission + resource sharing

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3
Q

Network benefits

A
  • allows devices to communicate/collaborate with each other, share peripherals/resources, and remote maintenance
  • manage users
    -access an intranet
  • access files from any networked computer
  • provide access to other networks e.g internet
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4
Q

Networks disadvantages

A
  • security risks -> vulnerability to malware (spreads easily between connected computers)
  • slower data transfer if high network traffic
  • server failure -> network downtime, connected computers stop working
  • initial expense: hardware and cabling
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5
Q

Server

A

computer designed to serve info and services to clients on network

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6
Q

Types of servers examples

A

Web server: serves web pages, processes scripting languages
Mail server: stores accounts, manages sending and receiving emails.
File server: centralised store, controls user access

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7
Q

Web servers

A
  • program
  • host websites and deal with client requests.
  • located via an IP address
  • when a website is visited, a request is sent to the web server.
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8
Q

Web client

A

program
runs on a user’s device
sends requests for web pages
Once web server processes request, client displays result of it

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9
Q

LAN

A

-group of computers connected
- over a small geographical area like a single site

  • internal infrastructure/hardware
    e.g cables/radio waves to connect
  • home, small business, school networks
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10
Q

WAN

A
  • group of connected computers over large geographical area
  • external infrastructure/hardware (cables, telephone lines, satellites, or radio waves to connect). often owned by 3rd parties
  • internet, international banking systems, and ATM machines
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11
Q

Internet

A

The internet is a global network of networks.
It allows computers on opposite sides of the globe to communicate with each other.
It is a giant mesh WAN (wide area network) made up of a series of smaller networks.
Continents are connected to each other using large international backbone cables, many of which pass underwater.
It is made up of interconnected networks, routers, cables, satellites, and other hardware spanning the world.
The World Wide Web is just a service on the internet.

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12
Q

Two types of network topology

A

All network topologies have both a physical aspect and a logical aspect
Physical topology refers to the physical layout of devices and cables in a network.
Logical topology refers to the way data is transmitted between devices on the network

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13
Q

Physical bus topology

A

All the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator.

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14
Q

Physical bus topology pros

A

● Relatively inexpensive to set up
● Doesn’t require any additional
hardware

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15
Q

Physical bus topology cons

A

● If backbone cable fails, the entire network gets disconnected
● As traffic increases, performance decreases
● All computers can see the data transmission

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16
Q

Physical star topology

A

A star topology uses a central switch or hub to connect devices in a network, with each device having its own cable connecting to the central node.

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17
Q

Physical star topology pros

A

Provides consistent performance even with heavy network traffic
Only one terminal is affected if a cable fails
Fast data transmission for better performance than bus topology
Easy to add new devices and manage from a central point
No data collisions, resulting in fewer errors
If a device fails, the rest of the network is unaffected

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18
Q

Physical star topology cons

A

Network fails if central switch fails
Can be expensive due to switch and cabling costs

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19
Q

Physical mesh topology

A
  • every node is connected to every other node, and each node acts as a relay to pass on messages to their final destination.
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20
Q

Physical mesh topology pros

A
  • No central connection point or switch, improving speed and reliability
  • Nodes are automatically incorporated and can handle high traffic volumes
  • No single point of failure, if a node in the route fails, the packet is sent a different way
  • Adding more nodes does not hinder the process as all nodes help to transmit data
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21
Q

Physical mesh topology cons

A
  • Expensive to set up, requires a large quantity of cables, and devices with wireless capability must be purchased if using a wireless network
  • Difficult to manage and maintain
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22
Q

protocol

A
  • a set of rules for data transmission and communication between devices
    on a network (for network protocol) or within a system
  • ensure technology-based standards are established and adhered to
  • Devices with different protocols cannot communicate, while devices with the same protocol can exchange information
  • allows user to communicate, by ensuring all devices follow the same rules/standards/ so they interpret data signals in the same way
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23
Q

standard

A
  • Standards are agreed-upon guidelines for hardware, software, or systems.
  • They ensure consistent performance and collaboration across different components and systems.
  • Various organizations create standards, including government bodies and industry associations.
  • Standards enable communication and data exchange across different platforms and systems.
  • They allow manufacturers to create compatible products and services.
  • Standards ensure communication between devices and applications using protocols.
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24
Q

Concept of layers

A
  • A divsion of network functionality
  • Divides the complex task of networking into smaller, simpler tasks that work in tandem with each other.
  • Each layer, with defined hardware and/or software, has a specific responsibility and provides a service to the layer above it.
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25
Q

layers benefits

A
  • Reducing complex problem into smaller sub problems. individual protocols are smaller and simpler to manage
    -different layers can interface with different hardware
    -devices can be manufactured to operate at a particular layer
    -products from different vendors will work together
    -self contained, can be removed or changed w/o affecting other layers
    -each layer has its own purpose, does not need to consider what other layers do, can program individually- Reducing complex problem into smaller sub problems. individual protocols are smaller and simpler to manage
    -different layers can interface with different hardware
    -devices can be manufactured to operate at a particular layer
    -products/systems from different vendors will work together - interoperability
    -self contained, can be removed or changed w/o affecting other layers
    -each layer has its own purpose, does not need to consider what other layers do, can program individually
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26
Q

TCP/IP stack

A
  • TCP/IP stack is a set of protocols used for communicating across the internet.
  • each protocol belongs to a different layer
    -data is further encapsulated as it is passed to the next layer
  • It organizes how data packets are communicated, ensuring that packets have source and destination, packet sequence, data, and error check.
  • The stack consists of four layers working together: Application layer > transport layer > network layer > link layer.
  • TCP splits data into packets, numbers them, reassembles packet and orders them at the other end, resends lost messages, detects errors.
  • IP locates the destination and routes packets over the network via routers.
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27
Q

Application layer

A
  • The application layer is at the top of the TCP/IP stack
  • It specifies the protocol needed to relate the application being sent
  • It encodes/decodes messages into a form understood by sender and recipient
  • Network applications such as web browsers and email programs operate at this layer
  • Protocols used at this layer include HTTP, HTTPS, SMTP, IMAP, and FTP.
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28
Q

Transport layer

A
  • The transport layer establishes an end-to-end connection using TCP or UDP
  • It breaks down data into packets and labels each packet with packet number, total number of packets, and port number being used for communication
  • It requests retransmissions of lost packets
  • Transport layer protocols use port numbers to track sessions and add this information to the header
  • It splits data into packets and numbers them for correct reassembly.
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29
Q

Network layer

A
  • The network layer adds source and destination IP addresses to packets
  • Routers use these addresses to forward the packets
  • A socket address combines the IP address and port number, specifying the device and application to send packets to
  • DNS is used at this layer
  • The network layer in the TCP/IP model packages data for transmission and routes packets using IP
  • All routers operate at this layer
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30
Q

Link layer

A
  • The link layer is part of the four-layer TCP/IP protocol model and represents the physical connection between devices.
  • The link layer adds MAC address information to packets for identifying the source and destination devices.
  • It enables the transfer of packets between nodes and networks using operating system drivers and NIC.
  • It adds the unique media access control (MAC) address of the devices to packets.
  • MAC addresses change at each hop when transmitting data between routers over a wide area network (WAN).
  • Communication between devices on the same LAN only requires the link layer using MAC addresses.
  • Communication between devices on different networks (WAN) requires both the link layer frame and the network layer using IP addresses.
  • Modern LANs also use IP addresses to treat the local network as if it were a wide network.
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31
Q

Step by step of a message through the layers of the TCP/IP stack

A
  • The original message is split apart and wrapped up in segments.
  • These segments are then wrapped up in packets which in turn are wrapped up in frames.
  • Once the frames reach their final destination, they will travel up through the layers of the TCP/IP stack in reverse order, stripping off the headers and tails as they go.
  • Finally the destination application receives the message
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32
Q

World Wide Web

A
  • The World Wide Web is a collection of files with information stored on hypertext (web pages) and other associated files, hosted on web servers.
  • Web servers host and store the files and handle client requests, such as HTTP GET requests for pages or resources.
  • Web pages are stored as text using languages like HTML, CSS, and JavaScript.
  • A web browser application is used to render the web page, using rules to display it correctly.
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33
Q

DNS (domain name system)

A

DNS refers to the entire system used to name and organize internet resources - including domain names and the DNS servers
DNS servers contain a database of website addresses and their corresponding ip addresses
DNS is hierarchical, with each smaller domain separated by a full stop - e.g ‘leeds.gov.uk’.
TLD stands for Top Level Domain, and 2LD stands for 2nd Level Domain.
Domain names are easier to remember than IP addresses and are used to link to servers.
The DNS server translates domain names into IP addresses when accessing a website.
- DNS contains many of domain name servers that translate human-readable URLs into IP addresses
- dns servers update eachother at regular points with changes

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34
Q

The process of a DNS lookup

A
  • User types a domain name into the browser e.g. www.amazon.co.uk
  • Browser checks its cache, if not found it performs a DNS search to locate the server
  • DNS system returns the IP address for that domain
  • Browser creates an HTTP request to get data from that IP address’ web server
  • Browser sends the domain name to a DNS resolver server
  • Resolver queries a DNS root name server which responds with the address of the TLD server for the domain (.com here)
  • Resolver makes request to .com TLD server and it responds with the IP address of domain name server
  • each part of the web address is handled by a different server
  • Recursive resolver sends a query to the domain’s name server (ANS)
  • IP address of google.com is then returned to resolver from name server
  • DNS maps the domain name to IP address and returns it to the browser
  • The requested web page or resource is returned to the client’s web browser
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35
Q

Data packets

A
  • Data packets are segments of data sent over a network.
  • Each packet contains a header, payload, and trailer.
  • The header includes the sender and recipient IP addresses, the protocol being used, the order of the packets, and the Time To
  • Live (TTL) or Hop Limit.
  • The payload contains the raw data to be transmitted.
  • The trailer contains a checksum or cyclic redundancy check used to detect errors during transmission.
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36
Q

Circuit switching

A

Circuit switching is a method of communication where a direct link is created between two devices, and the link is maintained for the duration of the entire conversation.
Data is transmitted in one long stream down the pathway from one node to another, resulting in data arriving in a logical order and quicker reconstruction of the data.
Circuit switching requires the two devices to transfer and receive data at the same rate.
Bandwidth is wasted during periods of time in which no data is being sent.
Using switches in circuit switching may produce electrical interference that can corrupt or destroy data.
Circuit switching ties up sections of the network which cannot be used by others until transmission has been completed.
Circuit switching enables two users to hold a call without delay in speech.
Circuit switching provides the basis for traditional telephone networks and is excellent for data that needs a constant link end to end, such as real-time video.
However, a lot of potential bandwidth can be wasted in circuit switching.

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37
Q

Packet switching

A

Packet switching breaks data into packets before sending them across a network
Each packet is marked with the source and destination and finds its own way to the destination
Multiple routes can be used, and packets can take different routes to their destination
Checksums and cyclic redundancy checks ensure data integrity
All bandwidth can be used at once, making it more efficient than circuit switching
Packets must arrive and be put in order before data can be received
Packet switching is more affordable and requires less complex infrastructure than circuit switching
Packets can be sent over very large networks to allow communication globally.

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38
Q

Circuit switching vs packet switching

A

Circuit switching establishes a dedicated physical path, while packet switching does not.
Circuit switching sends all packets on the same path, while packet switching allows packets to take different routes.
Circuit switching reserves bandwidth in advance, while packet switching does not.
Circuit switching does not support store and forward transmission, while packet switching does.
Circuit switching may cause bandwidth wastage, while packet switching eliminates this risk.

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39
Q

UDP

A

UDP is a communication protocol for sending short messages over a LAN/WAN.
It uses a simple connectionless transmission model and is an alternative to TCP.
UDP does not include error checking, making it less reliable than TCP.
It is often used for online gaming where speed is more important than accuracy.
UDP maintains an open two-way connection.

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40
Q

TCP

A

TCP is a communication protocol that uses a reliable transmission model.
It ensures accurate and sequential transmission of data
- it error-checking
TCP establishes a connection between two devices and maintains it for the duration of communication.
It is used for data transmission over the internet, including web browsing, file transfers, and email.
TCP is significantly more reliable than UDP.

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41
Q

HTTP

A

Stands for Hypertext Transfer Protocol.
Used for web page requests and delivery of HTML pages.
Fundamental protocol of the World Wide Web.
Allows for client and server to send and receive requests.
Used for web page rendering

42
Q

HTTPS - Hypertext Transfer Protocol Secure.

A

same as HTTP, but with added encryption and authentication.
Used for websites dealing with sensitive information like passwords or bank account details.
Provides an encrypted connection for secure communication between the client and server. Uses Secure Socket Layer (SSL) to encrypt data and the connection itself.
-encrypts/decrypts user page requests and pages returned by web server

process: client requests HTTPS session, server sends certificate, client creates a session key, session key is encrypted and sent to the server, the server decrypts session key using its private key, and the session being encrypted using the session key.

43
Q

FTP

A

FTP stands for File Transfer Protocol and is used for transferring files over networks
To use FTP, you need the IP address, FTP username, and password.
FTP follows a client-server model for sending and retrieving files.
FTP clients, such as FileZilla, are software applications that sit on top of the actual FTP protocol.
FTP commands are used to transfer files between computers on a WAN, with files being sent from the client to the server and vice versa.

44
Q

POP

A

POP stands for Post Office Protocol and is used for retrieving emails from a mail server. for mail access
When using POP, emails are accessed, downloaded, and removed from the server before being transferred to the user’s device.
This means that once an email is downloaded using POP, it will no longer be accessible on the mail server.

45
Q

IMAP

A

IMAP stands for Internet Message Access Protocol and is used for managing emails on a mail server and email access
When using IMAP, emails are kept on the mail server and a copy is downloaded to the user’s device.
IMAP allows for synchronization and management of email across multiple devices.
This means that changes made on one device (such as marking an email as read) will be reflected on all devices accessing the same email account using IMAP.

46
Q

SMTP

A

SMTP stands for Simple Mail Transfer Protocol
Used for transferring outgoing emails between servers and from email clients to servers
-send message from mail server to mail server
Enables email to be sent from one server to another and from email clients to servers
A fundamental protocol used for email communication
Often used in conjunction with POP and IMAP for email management

47
Q

Need for network security

A

Networks need protection from unwanted instruction and hacking
When computing devices are connected via a network, they become vulnerable to attack or misuse
The aim of network security is to only allow authorised users to access what they need, prevent unauthorised access, and minimise the potential damage caused by unauthorised access

48
Q

Proxies

A

A physical device placed between a network and a remote source
Collects and sends data on behalf of the user
Can handle web page requests and filter content
—-
-controls access of authorised users to data
-computer application that accesses data on a different computer system or network
————-
proxy servers
proxy server makes a we request on behalf of ur own comuter, hiding the true request ip addresses from the recpient
- proxy server enables anonymous surfing, can be used to filter undesirsable online content, logs user data with their requests, rovides a cache of precviosuly visited sites to speed access

49
Q

Benefits of Proxies

A

Protects user privacy and anonymity
Can cache frequently used website data for faster loading
Reduces overall web traffic
Can be used by administrators to control access to sensitive or irrelevant information at work or school.

50
Q

Firewall

A

A computer firewall is a utility that acts as a barrier between your network and the internet.
It examines incoming and outgoing traffic and blocks unauthorized access.
Firewalls can be hardware or software, or a combination of both.
Operating systems and home routers come with built-in firewalls, but they can also be purchased separately.
There are two main types of firewalls: Network-based firewall: and Host-based firewall

-hardware device/piece of software that monitors andf filters blocks traffic//placetd going to and from a entwork. it revents unahtorised access to a network, restrictd applictions that are used internally that have internal access and trestrict webs to be accssed within the compnay to protect the compnay;s data/intellectual properity

51
Q

Network-based firewall:

A

This type of firewall is implemented at the network level and is typically a hardware device, such as a router or switch. It filters traffic passing between a private network and the Internet, based on predefined security policies.

52
Q

Host-based firewall:

A

This type of firewall is installed on a single host and is typically a software application, such as the built-in firewall in most operating systems. It filters traffic based on rules set by the user and can be configured to allow or block specific applications or services running on that host.

53
Q

Packet Filtering

A

Limits network access based on admin rules
Examines source IP, destination IP, protocols, and ports
packets are either drop or rejected if denied by firewall
Rejected packets send alerts to the sender of the error
Dropped packets do not send alerts

54
Q

Secure Password Systems:

A

Require users to log in with predetermined credentials (e.g. username and password)
Can be made more secure by implementing password rules (e.g. minimum length, upper/lower case, numbers, password history, expiration)
Enforcing overly strict rules can cause users to write down their passwords, reducing security.

55
Q

Anti-malware software

A

often come pre installed with your operating system but can purchase others from dedicated vendors.

56
Q

Up-to-date software

A

Keeping software updated is important to ensure security
Early software builds can have flaws and bugs that can be exploited by malware
Patches are fixes developed by companies to address discovered flaws
It is crucial to keep operating systems and anti-malware systems up to date with the latest patches

57
Q

Hackers

A

Individuals who attempt to gain unauthorized access to a computer system, with the intent of stealing data, causing damage or disruption, or other malicious activities. To prevent hacking, it is recommended to use strong passwords, keep passwords safe, use a firewall, and regularly backup data.

58
Q

Black hat hackers

A

Hackers who use nefarious means to gain unauthorized access to computer systems, often with the intent of stealing company secrets or causing damage.

59
Q

White hat hackers

A

Security experts employed by a company who use their expertise to find vulnerabilities in computer systems and fix them, often referred to as “ethical hackers.”

60
Q

Gray hat hackers

A

Hackers who are not employed by a company, but still attempt to locate flaws in company-wide computer systems as a hobby. They may perform actions that are technically illegal, but they inform the company of the flaw so it can be fixed.

61
Q

Malware

A

Any computer code written with the intent to harm or frustrate, such as bots, keyloggers, viruses, ransomware, worms, and Trojans.

Effects of malware include: deleting, corrupting or encrypting files, causing computers to crash or slow down, reducing network speeds, and logging keyboard inputs and sending them to hackers.

62
Q

Viruses

A

A virus is a form of malware, malicious program that is capable of copying itself and spreading throughout a system.
They are typically designed to have a detrimental effect like corrupting a file system or destroying data.
To protect against viruses, use up-to-date anti-malware software and a firewall.
Avoid clicking on suspicious links or downloading suspicious attachments.

63
Q

Unauthorised access

A

Definition: The process of accessing a computer system without permission.

Tips to prevent unauthorised access:

Use strong passwords.
Keep passwords safe.
Use a firewall.
Regularly backup data.

64
Q

DOS (Denial of Service)

A

An attack on a computer system where an attacker attempts to overload the system by spamming it with a large amount of requests, making it difficult for the server to respond to legitimate requests.
Prevention: Using a firewall to block suspicious IP addresses and configuring web servers to block HTTP attacks.
Additional information:

DoS attacks can target web servers or high-profile organizations such as banks, e-commerce, and governments.
They typically do not result in the loss of data or other assets but can cost a great deal of time and money to handle.
Distributed denial of service (DDoS) attacks occur when multiple systems orchestrate a synchronized DoS attack against a single target, making it harder to prevent.

65
Q

Spyware

A

Spyware is a form of malware that covertly obtains information about a user’s computer activities by transmitting data from their device to a third party for analysis.
It can record actions, key presses, and other sensitive and personal data, such as internet surfing habits, email addresses, visited website pages, downloads, passwords, credit card numbers, and cookies.
To prevent spyware attacks, it is recommended to run up-to-date anti-spyware/malware software and use a firewall.

66
Q

SQL Injection

A
  • technique
  • exploits vulnerabilities in
    database websites/applications
  • malicious SQL code inserted into input
    form
  • e.g “where name =”B” OR 1=1”
  • executed by server -> errors/unintended operations
  • gain unauthorized access to the database

prevent by:
parameter queries (prepared statements), access levels. input sanitization, validation

67
Q

social engineering

A

Social engineering involves different manipulation techniques that exploit human error to obtain private information, access to a restricted system, or money.
It often involves scams or lures that trick users into exposing data, spreading malware, or providing access to a system.
People are often the weak point in social engineering attacks, as they may share passwords, lose memory sticks or laptops, leave printouts on desks, write passwords down on sticky notes attached to computers, fail to install updates, log off or lock computers, keep anti-malware up to date, lock doors to computer rooms, apply security to wireless networks, or encrypt data.
These risks can be mitigated through user training and education programs, but they can never be eliminated entirely.
Social engineering techniques include baiting, scamware, pretexting/blagging, phishing, pharming, shoulder surfing, quid pro quo, and vishing.

68
Q

Pharming

A

Pharming is a type of online scam that directs users to a fake website that mimics the appearance of a legitimate one, in order to obtain personal information.
The fake website is created using a piece of code installed on a PC or server, which redirects users to the fraudulent website without their knowledge.
To prevent pharming attacks, users should always log onto their internet banking directly and avoid clicking on suspicious URLs or emails that do not use their full name.
Additional measures like anti-malware and firewalls can also help prevent pharming attacks.

69
Q

Phishing

A

Phishing is an online fraud technique that tricks users into giving out personal information such as usernames, passwords, and credit card details.
Perpetrators disguise themselves as a trustworthy source in an electronic communication such as an email or fake website.
A phishing email typically contains a link that directs the user to a fake website that collects personal data when clicked.
To prevent phishing attacks, users should always log onto their internet banking directly and avoid clicking on suspicious URLs or emails that do not use their full name.
Network policies and firewalls can also help prevent phishing attacks by blocking access to known phishing websites.

70
Q

Network hardware

A

Routers
Switches/Hub
Wireless access points
Network interface card
Transmission media

71
Q

hub

A

A hub is a hardware device that allows multiple devices to connect to one network and sends data to multiple devices on that network.
The hub operates on the physical layer and is considered a passive device, meaning it simply broadcasts the transmissions it receives to all other connected devices.
Every packet of data is sent to every device connected to the hub, which can cause unnecessary network traffic and slow down data transfer.
Hubs are purely hardware devices and do not have any software installed on them.
Hubs are typically slower than switches in terms of data transfer.

72
Q

switch

A
  • interconnection device, allows two or more devices to be connected together
    -helps in solving issue of data collisions (if 2 or more computers place a packet onto a network at the same time, a data collision occurs. as a data packet arrives at the switch - its destination address is examined and switch creates a direct connection to that device)
    A switch connects multiple devices to a network and directs traffic only to its destination, rather than broadcasting it out to all devices like a hub.
    Switches generate a list of connected devices and use the MAC addresses of the devices connected to it to route data.
    Switches operate on the data link layer and are active devices that can inspect transmissions and route them to the correct device, keeping unnecessary traffic to a minimum.
    Switches are typically faster than hubs in terms of data transfer and have software installed on them for administration and configuration purposes.
    Switches are commonly used in networks with a star topology.
73
Q

modem

A

Modem is short for modulator/demodulator.
- enables a computer to connect to the internet over a telephone line.
Converts digital data into analogue signals for transmission over phone lines or other wiring/sent down the telephone line
then the modum on the other end Translates incoming analogue signals back into digital data for the computer to understand.
Typically has two ports: one for connection to the outside world and one Ethernet port for connection to a computer or router.
Connects to the WAN port on the router, with devices connecting to the other ports or via wireless connection.

74
Q

router

A

A router connects two or more networks together and is most often used to connect the internet to a home wireless network (WLAN).
or lan to wan

  • connects different networks together e.g home network to internet. has public ip address for lan and designates prviate ip addresses to network nodes.
    It directs packets of data to their destination in a network, receives packets from the network or internet, and forwards them to other computers on the network or internet.
    A router has a public IP address for the LAN and designates private IP addresses to network nodes.
    The router is connected to the internet service provider (ISP) typically via a telephone connection or fiber optic cable, which is in turn connected to a Domain Name Service (DNS) and other routers that make up the backbone of the Internet.
    Modern routers perform both LAN switching and WAN routing.
75
Q

multi-purpose devices

A

Modern network devices serve multiple purposes.
They combine functionalities like modem, switch, router, wireless access point, firewall, DHCP server, and more.
Modem/routers are commonly provided by ISPs and combine modem and router functionalities.
Modems and routers are different technologies.
Not all modems include routers and not all routers have modems.
Both modem and router are needed to connect to the internet.

76
Q

ethernet cable

A

Ethernet cable is used to connect devices together in a wired network.
Ethernet uses a networking standard, such as Cat 5e or Cat 6.
Ethernet cables are cheap and have a maximum transmission speed of up to 1Gbps, with a maximum distance for reliable communication up to 100m.
Twisted pair cables are made up of a pair of insulated copper wires and are generally used for telephone networks, data networks, and cable shielding.
Twisted pair cables can be affected by noise from external magnetic fields, but they are more affordable than coaxial and fiber optic cables.

77
Q

fibre optic cable

A

Fibre optic cables are often used for WAN or larger LANs.
They are expensive but very fast, with a maximum transmission speed over 40tbps and a maximum distance for reliable communication over 2km.
They have higher bandwidth and faster transfer speeds than other cables.
Data can be transmitted over long distances without any loss of signal quality and without suffering from electrical interference.
Fibre optic cables are made up of very thin optical fibres bundled together into a single cable, and can be made of glass or plastic.
They have the highest noise immunity due to light rays being unaffected by electrical noise.
They are commonly used to support long-distance connections between cities and countries, as well as data centres and organisations transmitting large volumes of data.

78
Q

coaxial cable

A

Coaxial cable is an older networking standard.
Made up of four cylindrical components: solid conductor wire, layer of insulation, grounding conductor, and layer of exterior insulation.
Provides moderate bandwidth and is more expensive than twisted pair but cheaper than fibre optics.
Can be affected by external magnetic fields but to a lesser extent than twisted pair.
Commonly used for computer network connections, digital audio, cable television, and feed lines that connect radio transmitters and receivers to antennas.

79
Q

Wireless Access Point (WAP)

A

Wireless Access Point (WAP) allows devices to connect to a network wirelessly through Wi-Fi/ allows wireless devices to connect to a wired network using WI-FI
- the AP (access point) usually connects to a router via a wired network as a standalone device but can be intergrated into router itself. like a wireless switch. provides internet in pinlic places (wifi hotspots)
Usually combined with a router to enable internet access and used in mesh networks.
WAP connects to a wired router, switch or hub via an Ethernet cable and projects a Wi-Fi signal within a designated area.
Signal strength weakens and possible wireless interference increases with distance and obstructions such as walls.
WAPs are commonly used in homes, offices, and schools where Wi-Fi coverage is needed.
Multiple WAPs may be needed for full coverage due to signal limitations and construction materials.

80
Q

NIC

A

A network interface card (NIC) is required for a computer to connect to a network.
NIC is built into most devices and assigns/contains a unique MAC address for the device
NIC allows for both wired and wireless communication on a LAN or a large-scale network.
NIC contains necessary circuitry for physical layer processes and some data link layer processes to run on it.
NIC allows Ethernet cable to be plugged into it and enables data packets to travel to and from a computer.
- a nic built into most devices that allows a computer to connect to a wired or wireless network

81
Q

Gateway

A

Gateway used when protocols differ between networks
It translates protocols to enable communication between networks
Removes header from packets and adds data using new protocol
Acts as an intermediary device between networks
Enables connectivity between networks with different communication protocols

  • provides a link between two dissimilar networks. it translates the protocols so that networks can communicate with each other
82
Q

client server

A

Involves a central computer (server) that processes and serves data to client computers (hough there can be multiple servers but clients still request data from the server).
consists of two parts, client and server.
Clients can request to use the server for resources and information
The network relies on a central server to manage and provide services - server controls access and security for a shared fire store, manages access to the internet, manages printing jobs, provides email services, runs regular backups of data.
Manage security, files held on server, some processing tasks preformend by server. Clients issue requests for services e,g email file storage backup printing. Can require reclaisit it staff to administer network
Suited for organizations with a large number of computers or situations where many computers need access to the same information

83
Q

client server pros

A

Data is more secure as it is stored in one central location
one location to backup. centered administred in one location
Centralized backups eliminate the need for individual backups
Resources can be shared between clients
All files can be stored centrally, allowing for easy user monitoring and access from any computer
Backups are central, eliminating the need for individual computer backups
Software can be upgraded centrally, eliminating the need to install on each computer
Central security measures, such as antivirus and firewall, can be administered in one location.

84
Q

client server cons

A

Expensive to set up and maintain
Functionality of terminals depends on the server
Trained staff required to maintain the server
Central point of failure
Requires IT specialists to maintain
Users will lose network access if the server fails
Cabling costs and specialized staff can add to the expense
A central server is needed for the network to function

85
Q

peer to peer

A

No central server; all devices have equal status
all computers can communicat with each other without going through a server. all computers can see files on other compurers.
devices on network share data.
no relience on company server and its connection to the internet. hasnt got to invest in lots of hardware and bandwidth and system more fault tolerant.
Files and data are shared between devices on the network
Each device acts as both a server and client, providing and requesting resources
Often used for file sharing and piracy due to difficulty in tracing origin of files
Peers responsible for their own security and data backup
Peers usually have their own printers, but can send print jobs to another peer to process if that peer is switched on and connected to the printer
Peer to peer model best suited for: smaller organisations with fewer computers or where fewer users need access to the same data at the same time

86
Q

peer to peer network pros

A

Cheaper to set up
Allows users to share resources
Easy to maintain
Not dependent on a central server
No specialist staff required
Decentralized and fault-tolerant
Can connect to other peers if one fails
No need for expensive hardware or central software installation.

87
Q

peer to peer network cons

A

Impossible to trace the origin of files
Backups must be performed separately
Poorer security
immpsoble to trace origin of files. poorer securitiy
May be difficult to locate resources
Decentralized - files stored on individual machines
Performance decreases as number of connected devices increases
Vulnerable to social engineering attacks and malware
Users need to manage their own backups
Difficult to maintain a well-ordered file store.
if cvomputer is switched off, data cannot be retieved from it.

88
Q

Why do we need both a MAC address and an IP address?

A

Every physical device has a unique MAC address.
Storing references to every MAC address in a router would be unmanageable - would take too long to find a particular address to decide which connection to route traffic down
Therefore switches learn and store MAC addresses for connected LAN devices only.
Routers cache some IP addresses.
MAC address identifies the device, while IP address identifies the device’s location.
MAC address tells who you are, IP address is where you are.

89
Q

Hosts on same network

A

Delivery is simple if two hosts are on the same network.
A host may need to broadcast first if it doesn’t know the destination MAC address - ARP protocol achieves this.
Traffic passes through the switch, which examines source and destination MAC addresses and learns which address applies to which device.
Eliminates the need for broadcasting in the future.

90
Q

Hosts on different networks

A

When sending data over the internet, all data is transmitted via a router.
The destination MAC address will be the router’s address.
The router works out where to send the packet by looking at the destination IP in the header.
The router then sets its own MAC address as the source and the next device as the destination.
If the router doesn’t know the destination MAC address, it uses the ARP protocol to find it.
If several routers are on the path to the destination, the source and destination MAC addresses will be overwritten at every hop.

91
Q

De jure (standard - latin for law)

A

standards approved by formal authorities. are critically accessed before being approved. e.g the ASCII character set

92
Q

De facto (standard, latin for reality)

A

standards which have been accepted as the best standard for their purpose. evolved to be accepted because of wide public support and market force. often because they have a proven track record for effiency and reality e.g QWERTY keyboard. Anyone can attempt to create a standard, liker inventing a new audio file format/ HTML replacement but its not de facto unless it gained popularity.

93
Q

SSID

A

identifies wireless devices

94
Q

LAN advantages

A

share hqardware (e.g printer)
share fi;es
share internet connection
centralised security
log on/access files from any machINE on
the lan
central maintenance]
central backup/storaghe
central instalation/update of programs
can monitor user activity
can control access levels//centralised user admin
access an intranet (companys version of an internet)

95
Q

IP address
e.g 212.58.244.210

A

numerical address made out of 4 numbers between 0 - 255
each number is a byte of data
that uniquely identifies a device on the network
its a logical identifier (i.e the IP address can change e.g if you take your laptop home)

96
Q

packet switching advantages

A

multiple methods to ensure data arrives intact e.g checksums and cyclic redundancy checks

multiple routes can be used between devices, so if one path breaks, another can be used

packets can be transferred over very large networks to allow communication globally

97
Q

packet switching disadvantages

A

time is spent deconstructing and reconstructing the data packets

must wait for all packets to arrive before data can be received

98
Q

circuit switching advantages

A

data arrives in a logical order which results in a quicker reconstruction of the data
enables two users to hold a call without delay in speech

99
Q

circuit switching disadvantages

A

bandwidth is wasted during periods of time in which no data is being sent
devices must transfer and receive data at the same rate
using switches means electrical interference may be produced which can corrupt or destroy data
ties up sections of the network which cannot be used by others data until transmission has been completed

100
Q

hub vs switch

A

siwtch: joins compuers/devices together in lan. receives packets/data. recpient’s address is given in packet header, it uses mac address. sends packets/data. out the correct port/to specific computer device.

hub - connects devices together. receives data and broadcats spacket to all devices on network

A Level Computer Science (25 decks)

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