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Fundamentals of computer networks (Network protocol: a set of rules for…
Fundamentals of computer networks
Computer Network
: is more than one computer or device, connected together so that they can communicate
Benefits
can share resources e.g. printers
can share data
can install and update software on all computers at once
can central back-up
user accounts - can log onto any computer
Drawbacks
If a central server fails, all computers may not work
If a virus infects one computer, it may spread across the whole network
Data can be less secure as any computer on the network could be hacked
Can be expensive to install and manage (employ a network manager)
PAN
: Personal Area Network
Usually enables data transfer between 1 person's devices EG Laptop, Smart Phone, Printer
Usually uses Bluetooth connections
LAN
: Local Area Network
Computers connected in a relatively small geographical area
Often owned and controlled by a single person or organisation
WAN
: Wide Area Network
cover a wide geographical area
Internet is the biggest example of WAN
are often under collective or distributed ownership
Network Connections
WIRED
Fibre Optic - Fast & expensive - can transmit over very large distances at a high bandwidth
use from servers to switches
Copper wire - slower & cheaper
use from switches to computers
more reliable
more consistant speed
more secure
WIRELESS
Needs Wireless Access Points around a building - WAP is basically a switch that allows devices to connect wirelessly
ADVANTAGES
cheaper and better for environment as no wires needed
convenient - can automatically connect and can move around whilst connected
easy to add more users - don't need to install extra wires or do any complex setup
DISADVANTAGES
generally less secure - access points are usually visible to all devices
distance from WAP, interference from other wireless networks, and physical obstructions can all reduce signal strength
they generally have a lower bandwidth and are less reliable
NIC
: (Network Interface Card - piece of hardware inside a device that allows it to connect to networks
Topologies
STAR
: all devices connected to the centre
ADVANTAGES
if a device fails or a cable is disconnected the rest of the network is unaffected
simple to add more devices
tend to have better performance than other setups - all devices can transmit data at the same time
very few data collisions
DISADVANTAGES
expensive - every device needs a cable
switch itself is expensive
if there is a problem with switch or server the whole network is affected
the maximum number of connections depends on the switch
BUS
: All work stations and peripherals connect to the 'backbone' cable, that has terminators at each end which stop data reflecting back along the bus
ADVANTAGES
network is unaffected if a device fails
aren't dependant on a central with to keep the whole network running
cheaper - much less wire is needed & the bus cable and terminators are cheaper than switches
DISADVANTAGES
data collisions are common - data must be resent which slows the network down
the more devices, the more likely data collisions are - unsuitable for large networks
devices must wait for the bus to be available to avoid collisions - slows network
Network protocol
: a set of rules for how devices communicate and how data is transmitted across a network
Ethernet
: a family of protocols that operates on the link layer - handles the transmission of data between devices on LANs - specifically for wired connections
WiFi
: is a trademark for WLANs. It is a family of protocols - handles the transmission of data between devices on LANs
TCP
: (Transmission Control Protocol) establishes a connection between the sending and receiving devices. It then splits the data into numbered packets that can be reassembled into original data once they reach their destination, even if they arrive out of order
UDP
: ( User Datagram Protocol) breaks the data down into packets without numbering them. They are read by the receiving device in the order that they arrive - even if that's not they order they were sent
IP
: (Internet protocol) responsible for directing data packets to their destination using a process called packet switching
HTTP
: (Hyper Text Transfer Protocol) used by web browsers to access websites and communicate with web servers
HTTPS
: A more secure version of HTTP
FTP
: (File Transfer Protocol) Used to access, edit and move files between devices on a network
email protocols
SMTP
: Used to send emails. Also used to transfer emails between servers
IMAP
: Internet Message Access Protocol) Used to retrieve emails from a server
Network security
: organisations need to keep networks secure from hackers in order to protect sensitive information and comply with data protection laws
MAC address Filtering
: a way of making sure the only people on a network are trusted users. It checks the MAC address of each device that tries to connect to the network and only lets allowed devices join the network
Encryption
: data is translated into code which only someone with the correct key can access - essential for sending data over a network securely
Firewall
: examine all data entering and leaving a network and block any potential threats
Authentication
: prevents unauthorised people from accessing data from the network
TCP/IP Model
Application Layer
providing networking services to applications
HTTP, HTTPS, SMTP, IMAP, FTP
Transport Layer
Setting up communications between two devices, splitting data into packets and checking packets are correctly sent and delivered
TCP, UDP
Internet Layer
Adding Ip addresses to data packets, directing them between devices and handling traffic. Used by routers
IP
Link Layer
Passing over the physical network. Responsible for how data is sent as electrical signals over cables, wireless and other hardware
WiFi, Ethernet