Networks Flashcards
Standalone computer
A computer that is not connected to a network
Network
An arrangement(or group or setup) of two or more computers that are connected together for the purpose of sharing resources and/or data.
Internet of Things (IoT)
A network of physical objects that use sensors, actuators, embedded systems and wireless technology such as WiFi, Bluetooth and Zigbee, to collect and exchange data, with minimal or no human interaction.
VoIP
Voice of Internet Protocol
LAN
Local Area Network
Example:
- School network
WAN
Wide Area Network
Example:
- Bank network
WLAN
Wireless Local Area Network
Example:
- Hand held scanners
Server
A computer connected to a network used to coordinate(store and share) vast amounts of data.
Latency
The time it takes for a message to transfer (ms). Also known as ping.
Internet
- An interconnected network or network of networks.
- Most networks are part of the internet.
- Consists of multiple cables or links that connect countries together, and can be though of as the backbone.
Packet switching
- Breaking down a large amount of data into small packets, each packet is independent of one another.
- Each packet is tagged (has a header) with the recipient and source IP, checksum and a sequence number for the packets to be put back in order at the destination and checksum
Server
A computer connected to a network used to coordinate(store and share) vast amounts of data.
Network topology
A Network Topology is the arrangement with which computer systems or network devices are connected to each other.
Bus topology
In a bus topology, all nodes in the network are connected directly to a central cable that runs up and down the network.
Advantages:
- Cheap since little cabling needed
- It still works if a node fails
- Easy to add extra devices
Disadvantages:
- If the central cable is damaged the network stops working
- More devices, slower since more collisions
- All nodes can access all traffic can be security risk
Ring topology
In a ring topology network, each node is connected to two other devices.
Star topology
In a star topology, all nodes indirectly connect to each other through one or more switches. The switch acts as a central point through which all communications are passed.
Advantages:
- Still works if a node fails
- Damaged cable doesn’t stop the network from working
- Data traffic only sent to intended recipient, secure
- Easy to add extra nodes
Disadvantages:
- If central node fails, network stops working
- Network capacity depends on central node’s capacity
- Many cables, expensive and difficult to set up
Mesh topology
In a mesh topology, there is no central connection point. Instead, each node is connected to at least one other node.
Advantages:
- Very fault tolerant, if a connection fails, message is re-routed
- Nodes can be added/removed without having take network offline
- Very scalable
- Very high performance, each node is connected to many other nodes
Disadvantages:
- Many cables, difficult and expensive to set up
Router
Manages communication on the network. Can have a built-in wireless access point (WAP).
TCP
- Transmission Control Protocol
- Responsible for delivering data to a given address (packet switching)
- Transport layer
Modem
Modulator/Demodulator
HTTP
- Hyper Text Transfer Protocol
- Application layer
SMTP
- Simple Mail Transfer Protocol
- Application layer
IP
- Internet protocol
- Responsible for obtaining the address to which data is sent.
- Internet layer
TCP/IP
- Layered protocol stack (Application layer, Transport layer, Internet layer, Link layer)
- Collection of protocols
- It sets how data should be formatted and transmitted across networks
Web server
Holds and shares web pages
File server
Holds and maintains user files
Mail server
Handles emails between users
Methods to protect networks
- Access control: Ensures that only authorised users can access the network and its resources
- Authentication (User management) : Ensures that users can only access data relevant to them
- File permissions: Prevents misuse: deleting/copying data, installing software
- Physical security: Prevents damage to hardware
- Firewall: Acts as a barrier between an organisation’s internal network and the internet. Inspects incoming and outgoing data traffic and decides what data to allow through
Importance of network security
- Business success: data on the network is vital for running an organisation, it might fail if comprimised
- Privacy: data on the network might be sensitive
- Financial: the data might be financially valuable
Vulnerabilities of the cloud
Cloud data centres attract many attacks due to the vast amount of information stored, sensitive data is best stored locally.
Ethical hacking
Looks for weaknesses in software and systems by trying to penetrate into them so that they can be addressed.
Penetration testing
Used to test a computer system or network in order to find vulnerabilities
Social engineering
Exploiting human behavior. The attacker will ‘engineer’ a situation where the target individuals give away confidential information
Unpatched software
Someone can exploit a vulnerability in an unpatched (unfixed) software that still has that vulnerability
Anti-malware software
Prevents infection by malware by searching for it and destroying it
Encryption
Scambles data for anyone who doesn’t have the key to unscramble it.
Asymmetric encryption
- Uses two different keys
- Every user has two keys (public and private)
- A message encrypted with a public key can only be decrypted with its private key
Symmetric encryption
- Uses one key
- Encrypts and decrypts data using the same key
- Both ends of the transmission must know the exact shared key
Symmetric encryption
- Uses one key
- Encrypts and decrypts data using the same key
- Both ends of the transmission must know the exact shared key
Link layer
- Ethernet
- Wi-Fi
Internet layer
IP
Transport layer
TCP
Application layer
- FTP
- HTTP
- HTTPS
- SMTP
- POP
- IMAP
POP
- Post Office Protocol
- Used by a client to retrieve emails from a mail server, message deleted on download, it will be stored on the device it was read/downloaded from
IMAP
- Internet Message Access Protocol
- Similar to POP but messages can be read and stored on the message server. The message left on the server on read. Hence accesible from any device
Package switching verification
- Checksum for package computed before leaving the computer
- Checksum added to the header
- At recipient, checksum is re-computed
- If don’t match, re-send request is sent back
