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1.4 and 1.5 Networks


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Internet
A collection of inter-connected networks
Wide Area Network
Uses third party (e.g. BT) cabling to transfer data between computers across the network e.g. the internet
Local Area Network
Computer network that spans a relatively small area e.g. school, hospital etc
DNS Server
Uses a database of website addresses and their IP addresses to allow a user to access websites
DNS advantage
Website address is easier to remember than an IP address
DNS advantage
A connection to one DNS server means that you can access all addresses on all DNS servers
Protocol
A set of rules
Network cabling
Copper cable/twisted pair/Fibre Optic
Encryption
Encoding of data so that it can no longer be understood by humans
Bandwidth
The amount of data that can be transferred at one time
Latency
The speed that data travels during transfer (or delay in receiving)
Error rate
The number of collisions in high network traffic
Retransmission rate
How promptly corrupted or lost packets can be resent
Wifi signal factors
Walls, other devices, neighbours networks using overlapping channels
Network Interface Card
Computer hardware component that connects a computer to a computer network
MAC Address
Unique identifier assigned to network device
Wireless Access Point
Networking hardware device that allows a Wi-Fi device to connect to a network
Wifi Channel
One subdivision of the main frequency
2.4GHz advantage
Greater range = Better signal/compatible with more devices
2.4GHz disadvantage
Slower data transmission/interference from other devices.
5GHz advantage
Less crowded with 23 non overlapping channels/high data transmission rates
5GHz disadvantage
Less able to penetrate through walls/Poorer compatibility
Plaintext
The original message to be encrypted
Ciphertext
The encrypted message
Key
A sequence of numbers used to encrypt or decrypt
Encryption algorithm
The formula for encrypting the plaintext
Private key encryption
Single key is used to encrypt and decrypt a message and must be given to the recipient of your message to decrypt the data
Public key encryption
Two keys are used - one to encrypt and the other to decrypt data
Public key advantage
More secure as it means that you never have to send or reveal your decryption key
Ethernet networking protocols
set of rules governing how, when and in what format network data should be sent
Ethernet transmission
Data is split into frames, similar to Internet data packets. Ethernet also manages transmission errors
Virtual Network
Network does not consist of a physical (wired or wireless) connection between two computing devices
Router
Passes data packets across a network towards their final destination
Switch
Smart multi-plug adaptor only sends packets to the intended recipient, using its MAC address
Hub
Central, multi-plug adaptor that when a packet of data is received, it broadcasts the packet to all devices on the network
Star
Each computer is connected individually to a central hub which can be the server or a hub or switch
Star Advantage
Fast data transfer as there are fewer data collisions
Star Advantage
If one cable fails the other workstations are not affected
Star Disadvantage
Requires additional hardware such as the central switch
Star Disadvantage
If the central device fails the whole network goes down
Network Advantage
Sharing resources such as printers saves money
Network Advantage
You can access your files from any computer in the network
Network Advantage
Data is easy to back up as it is stored centrally on the server
Network Disadvantage
Purchasing the network hardware is expensive
Network Disadvantage
Managing a large network is complicated
Network Disadvantage
Viruses may be able to infiltrate the network and infect every computer
Mesh Network
Nodes act as routers for data in order to relay and spread data in the network
HTTP(hypertext transfer protocol)
Accessing and receiving web pages in the form of HTML
HTTPS (secure protocol)
Encrypts the information so that it cannot be understood if it is hacked
FTP (File Transfer Protocol)
sending or retrieving files to or from a remote server or computer
POP
Download entire messages to your local device and delete them from the server
IMAP
Only download the message header until the message is opened and will leave the message on the server
SMTP (Simple Mail Transfer Protocol)
Transferring email between remote email servers
TCP (Transmission Control Protocol)
Breaks up and reassembles messages sent over the Internet into small chunks called packets. Detects errors and Resends lost messages
IP protocol
Routes the individual packets
TCP/IP protocol stack
Defines four layers in which different protocols operate to pass data packets across a network
DNS step 1
1) a website address (domain name) that is entered is looked up in a DNS database to find the matching IP address
DNS step 2
2) if it can�t find the address, it searches on other DNS servers
DNS step 3
3) Once found the IP address of the website is accessed to retrieve the data
DNS step 4
4) This data is then sent back to the user who can then view the website