Networks Flashcards
Network
A group of devices connected together so they can communicate with each other and share resources.
Why are computers connected in networks?
- Share data and info
- Communicate using email, messaging, video conferencing
- Collaborative work
- Share hardware
- Centralised support and maintenance
- Socialisation
LAN
Local Area Network
Infrastructure owned and maintained by the organisation.
WAN
Wide Area Network
Telecommunications links managed by other companies.
Organisations that run their own WANs will often lease bandwidth from telecommunications companies.
Others cannot use its’ infrastructure, making it secure. However, the infrastructure can be expensive to install and maintain.
Wired
Harder installation
-> (each device has a dedicated cable)
Difficult to diagnose problems
-> (all cabling needs inspection)
Cannot move around
-> (limited to area covered by cable)
Longer range
-> (copper is better at signal transmission than air)
Larger bandwidth
-> (copper is better at signal transmission than air)
Better latency
-> (less susceptible to interference from outside sources as the cables have coverings to protect them)
Wireless
Wireless may save cabling costs
-> Not every device needs a dedicated cable
WAPs still need to be installed
-> Diagnosing problems is easier
Lower range
-> Quality lost through floors and barriers between device and WAP
Lower bandwidth
-> Transmission through air doesn’t support high speeds
Lower latency
-> Radio waves disperse over large distances, slowing data transfer
Protocols
Sets of rules that govern the communications within devices.
For two devices to communicate, they must use the same protocol.
Network protocols
Ethernet
Wifi
TCP/IP
HTTP
HTTPS
FTP
Email protocols
POP3
SMAP
IMAP
4 layer protocols (ATIL)
Application
Transport
Internet
Link
Internet
Largest hardware network of networks
POP3
- Post Office Protocol.
- Used by email clients to retrieve email.
SMAP
- Simple Mail Access Protocol
- Accessing email stored on a server.
IMAP
- Internet Message Access Protocol
- Enables access to emails using multiple email clients
TCP/IP
- Transmission Control Protocol / Internet Protocol
- Protocol stack used when connecting a device to the internet.
HTTP
- Hypertext Transfer Protocol
- Governs communication between webserver and client
HTTPS
- Hypertext Transfer Protocol Secure
- Secure encryption for transactions to be made over the internet
FTP
- File Transfer Protocol
- Governs transmission of files across a network and the internet
Application
The application layer is the one which users interact with.
The protocols in this layer are responsible for the rendering of web pages, the packaging of emails, and other such user-based interactions.
Transport
The transport layer is responsible for establishing a virtual channel between two devices.
This is also where data is broken up into packets ready for sending.
This is where data packets are joined back together on the destination end.
Internet
Also known as the network layer.
This is where source and destination addresses are added to the data packet.
An identifier for the protocol responsible is also added so that routers along the way know it’s IP.
Link
Also known as the network interface layer.
The link layer is responsible for defining how data is transmitted across connections.
Bus network
A central node with stops coming off it.
All data stops at every node in order to reach its’ address.
This increases latency, lowers bandwidth and makes it easier for hackers to penetrate a system.
Star network
A central switch with spokes coming off it
More secure if there is an intrusion. Data only passes through the switch and computer, so each PC only receives its’ own traffic.
Higher latency, however limited connections to other computers based on ports in switch. If the switch fails, all computers connected are stranded to a single central point of failiure.
Mesh network
All nodes connected to each other.
Decentralised
Data can still be routed to destination address even if one node fails
How to identify network vulnerabilities
Penetration testing
Ethical hacking
Importance of network security
chat am i tweaking?
Methods of protecting networks
Access control
Physical security
Firewalls
WLAN
Wireless Local Area Network
Wireless Access Point
WAP - In WLAN. Broadband router wired to an internet access point
How are network speeds measured
Bits per second
Range
Distance at which communication is reliable
Wired - Up to 100m for Ethernet
Wireless - Up to 50m
Latency
the time taken for a transmission to reach its destination. It is measured in milliseconds.
Ping measures latency by making a transmission and tracking the time it takes to move from the server and back again.
Bandwidth
maximum amount of data that can be transmitted over a connection. It is a measurement of capacity measured in bps (bits per second)
Packet
Data transmissions broken up into smaller, more manageable examples called packets
Contents of a package
Header
-> Address, sequence number, checksum, type, time
Payload
->Data
Footer
-> Marks end of packet.
Lifespan of a packet
- Click download
- Server containing image receives request via Internet
3.Image broken up into smaller parts - Each part put into packet + your IP
- Packets make their way across internet to your IP address
- Computer rearranges packets in order.
6b. If any packets are missing, computer requests resend.
It’s sort of like mail.
Routing
Network routing is the path a packet takes when it travels from its source to its destination.
The router uses its’ routing tables to move the packet by one step.
Packets are sent outside local networks when the network portion of the IP address is different from its’ own.
Routers
A routing table stores direct connections to other network destinations.
Routers use routing tables to move packets towards their destinations.
Routers don’t know the contents of other routing tables.
Packet switching
Routers send each packet along a connection to another router, choosing the path which has the least traffic already present.
This means packets may take different routes to their destinations.
