Networks Flashcards
1.3.3
What is a network?
Name given to two or more computers connected with the ability to transmit data between each other
What is a LAN?
Local Area Network is a network that spreads over a small geographical area
What is a WAN?
Wide Area Network is a network that spreads over a large geographical area
What is a protocol?
Set of rules defining how two computers should communicate with each other ensuring secure data transmission and making sure they interpret data the same way
What is HTTP?
HyperText Transfer Protocol which is used for web page rendering
What is TCP/IP?
Transmission Control Protocol/ Internet Protocol used for routing packets through networks
What is POP3?
Post Office Protocol are mailing protocols used for email access
What is FTP?
File Transfer Protocol used for the transmission of files over networks
What is the internet?
A network of networks which allows computers on opposite sides of the globe to communicate with each other
What does the Application Layer do?
Interacts directly with software applications
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)
What does the Transport Layer do?
-Uses TCP to establish an end to end connection between the source and recipient computer
-Splits data up into packets and labels packets with packet number, total number the original packet was split up into and port number for communication
-If any packet gets lost, transport layer request retransmission of lost packets
What does the Internet Layer do?
-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
-Responsible for routing each packet across the network using the IP addresses in the headers
What does the Link Layer do?
-Receives packets from the Internet layer
-Adds the MAC address of the sender and receiver to the data before transmission
-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 then translates it back into digital packets
For devices on the same network what is the destination MAC?
The MAC address of the first router that the packet will be sent to
What does each packet contain ?
-Payload(data)
-A header(With metadata and destination IP addresses)
-A footer(to signify end of packet)
What is the DNS?
Domain Name System is a directory of domain names and is used to translate human-readable domain names to numeric IP addresses that computers use
What are the benefits of DNS?
-Allows us to use easily remembered domain names instead if hard to remember IP addresses
-Handles mapping between domain names and IP addresses, relieving end users and system administrators from the task
What happens when you type a URL into a web browser?
(LONNNNGGGGG ASFFFF)
1️⃣User enters URL in a web browser
2️⃣ Computer checks cache for the IP address
3️⃣ Browser queries DNS resolver if IP is not cached
4️⃣ Resolver contacts DNS servers (Root → TLD → Authoritative)
5️⃣ Authoritative DNS server returns IP address
6️⃣ Browser sends request to web server at that IP
7️⃣ Web server responds with webpage data
8️⃣ Browser renders the webpage for the user
What are the advantages of LAN?
Centralised management
Security-Can secure devices with use of firewall, antivirus software
File Sharing-Allows users to share resources, files, and folders
What are the disadvantages of LAN?
If hardware fails network may not function properly
May be more prone to attacks
Accessing data and peripherals may be slow
Needs regular maintenance to ensure software up to date
Why are protocols divided into layers?
-Modular design meaning breaking complex process of networking into more manageable layers
-Interoperability-meaning that protocols that operate at network layer can be altered independently of application layer protocols
-Ease of updates-Changes can be made to one layer without affecting another making updates and improvements easier to implement
-Specialisation-Each layer can be specialised to preform its functions without worrying about specifics of other layers. Allows for more effective and efficient design
What information do headers contain?
Source IP address: identifies the sender of the packet
Destination IP address: identifies recipient
Sequence number: helps in reordering packets into original message
Protocol: identifies transport protocol
Packet Length: Indicates size of packet
Checksum: a value used for error checking
What is packet switching?
Network communication method that breaks down data into smaller packets and sends them separately along different routes and reassembles them at the destination
What are benefits of packet switching?
Efficient as packets can follow different paths using more of available bandwidth
More reliable as if a single packet fails only that packet needs to be sent not the whole stream
Lower cost due to shared network resources
What are disadvantages of packet switching?
Not ideal for real-time services like video calling as it requires a steady stream with no data delays
Packets can arrive out of order so reassembly is required
Potential for congestion in the network
What is circuit switching?
Communication method where a dedicated communication path is established between two devices for duration of conversation and all packets sent along same route
What are advantages of circuit switching?
Ideal for real-time services as it has a steady data transmission rate
No delays as dedicated path is established
Data arrives in order as it follows same path
What are disadvantages of circuit switching?
Less efficient as resources remain allocated during whole conversation even when no data is being sent
More costly due to dedicated line requirement
Less flexible and scalable, as adding new devices can be complex
What are hackers?
Individuals or groups of individuals who exploit system vulnerabilities to gain unauthorized access to data for personal gain, activism or cyber espionage
What is a virus?
Malicious software programs designed to spread from one computer to another and interfere with normal operations
A virus attaches itself to a legitimate program or file and them replicates itself to spread to other programs or files on the computer, causing damage by deleting data or damaging hardware
What is malware?
Malicious software designed to harm or gain unautherised access to a systems network
What is a worm?
Similar to a virus but is a standalone program that can spread and replicate itself over computer networks. Can take up storage or bandwidth
What is a trojan horse?
A program that disguised itself as a legitimate program or file but when installed it can delete or damage hardware
What is spyware?
Malware designed to secretly monitor a user’s activity on their computer or device without their knowledge.
It can gather sensitive information like passwords, browsing habits, and personal details, and send it to a third party
What is adware?
Software that displays unwanted advertisements on computer screen without users consent. Some may contain spyware when clicked and link to viruses
What is ransomware?
Malware that encrypts the users file and demands a ransom payment to decrypt them. Can cause data loss and financial damage
What is a DoS attack?
Dos attack is when a computer floods a server with a lot of requests at the same time, which the computer cant respond to, causing it to crash
Aims to disrupt normal functioning of a system or network by denying user access
What is a DDos attack?
Similar to DoS but instead multiple computers are used as bots to send requests to the server
What is Phishing
Attempting to acquire sensitive information by masquerading as a trustworthy person in electronic communication
Involves sending an email that looks legitimate
Email contains link to fake website where user is encouraged to enter details to steal sensitive information for personal gain
What is Pharming?
Cyber attack intended to redirect websites traffic to another bogus website
Involves malware being downloaded without users knowledge
Redirects user to a fake website where they’re encouraged to enter personal details
What is social engineering?
Involves manipulating individuals to gain access to confidential information to benefit the attacker
What is a firewall?
Network security systems that monitor and control incoming and outgoing network traffic
How does a firewall work?
Firewall consists of two NIC’s between internal and external network passes packets between them and compares against set of rules by firewall software by packet filters
What are packet filters?
Limits network access in accordance with administrator rules and policies
Works by examining source IP, destination IP and protocols being used as well as ports being requested to decide whether they are accepted
What are proxies
An intermediary, collecting and sending data on behalf of the user
What are the benefits of proxies?
Privacy of user is protected and they remain anonymous
Can cache data of frequently used website data making it faster to load
Can be used by administrators to prevent access to sensitive or irrelevant information at work or school
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
What is a modem used for?
Enables a computer to transmit data over telephone or cable lines by converting digital signals into analogue or vice versa for receiving data
What can a modem be used for?
DSL, cable, or dial-up internet connections
What is a router?
Network device that routes data from a LAN to another network connection
Joins two networks together
How does a router work?
Analyses data packets and determines the best path for a packet to reach its destination
If data packet is coming into the LAN, it will read the header of the packet to determine the intended destination IP address
Might have to travel through several routers to get to its destination
Each pass from a router is called a hop
it will then forward the packet to its destination
What are cables?
Physical paths for data to travel between devices in a network
What are fibre-optic cables?
Cables that use light to transmit data, offering much higher speed and larger capacity
What is an NIC?
A hardware component that enables a device to connect to a network
Provides dedicated, full-time connection to a network converting the computers data into a network friendly format
What is a WAP?
Device that allows wireless devices to connect to a wired network using Wi-Fi.
It acts as an interface between the wireless network and the wired network (e.g., Ethernet).
It broadcasts a wireless signal that devices can connect to
What is a Hub?
A network device used to connect multiple devices in a network
They pass anything received to all devices on network
But are cheap
Why are hubs bad?
It will broadcast data to every device on the network, causing unnecessary traffic
Poor security
What is a switch?
Network device that connects devices on a network and uses packet switching to receive, process and forward to the destination device
Only sends to the device its intended do
How does a switch work?
Switch only sends the data to the intended device by a lookup table
When a switch receives the data packet it examines the destination MAC address and looks up that address in its lookup table
Once its found the matching MAC address it will then send to corresponding port
What is a client server network?
Powerful and reliable computer that control the network and serve the clients with services such as files, emails etc and services to be consumed by clients
What are advantages of client-server?
Better security since files stored in central location
Backups are done automatically
Data can be shared
What are disadvantages of client-server?
If server goes down all services could be unavailable
Can be expensive to set up and maintain
What is a Peer-to-Peer Network?
All computers in the network share responsibility and there is no central server
All machines have equal status
All responsible of their own security and backup
Data spread across the network
What are benefits of Peer-to-Peer?
Easy to set up and less expensive than client
No dependency on a central server
Data can be shared directly between systems no need for central server
What are disadvantages of Peer-to-Peer?
Lack of control can lead to vulnerability and issues
Not suitable for large network as it can have performance issues
What does the term standard mean?
The set of guidelines that govern how a task should be performed in data transfering
Why do we need standards?
Enables different device regardless of model to work together
Ensures data can be correctly interpreted by receiving device regardless of how it was sent
What is API?
A set of rules and protocols that allows different software applications to communicate.
Functions of APIs?
Sets out formats of requests and responses between server and client and enables one application to make use of the services of another
What is a Thin Client?
A lightweight device that relies on a server for processing, storage, and applications.
Pros of Thin Client?
Easy to maintain(most data and apps are on the server).
Lower cost due to minimal hardware requirements.
Cons of Thin Client?
Requires constant network connection to function.
Server failure affects all thin clients.
What is a Thick Client?
A device that performs processing locally and stores applications/data.
Pros of Thick Client
Can work offline without a network connection.
Better performance for local tasks (e.g., running apps).
Cons of Thick Client?
Higher cost due to more powerful hardware.
More maintenance needed for each individual client
What is Server-Side Processing?
Processing that occurs on the server in response to requests from the client.
Tasks Handled by Server-Side Processing?
Database queries (retrieving/storing data).
Data validation (checking input).
Pros of Server-Side Processing?
More powerful, can handle complex tasks.
Data securely stored on the server.
What is Client-Side Processing?
Processing that occurs on the client’s device (e.g., computer or smartphone).
Tasks Handled by Client-Side Processing?
User interface interactions (e.g., buttons, forms).
Dynamic updates on the page (e.g., form validation).
Immediate feedback to the user (e.g., checking email format).
Pros of Client-Side Processing?
Faster response time (doesn’t rely on server for every task).
Reduces server load (less processing on the server).
When to Use Server-Side vs. Client-Side Processing?
Server-side: Complex tasks, secure data processing.
Client-side: Simple, interactive tasks, UI feedback
Cons of client side
Potential security risk as clients can see code
Reliant on JavaScript so if it doesn’t work page is inaccessible
Cons of server side
Slower response time
Increase server load
Heavily dependent on server
