3.2 Wired and wireless networks Flashcards
Addresses
Devices on a network send and receive data, a device needs an address to ensure it sends data to the correct place
There are two types of network address systems:
IP Address
MAC Address
Internet protocol (IP) address
An IP (Internet Protocol) address is a unique identifier given to devices which communicate over the Internet (WAN)
IP addresses are dynamic, they can change.
IP addresses make it possible to deliver data to the right device.
A device connecting to a network will be given an IP address, if it moves to a different network then the IP address will change.
IPv4
Internet Protocol version 4 is represented as 4 blocks of denary numbers between 0 and 255, separated by full stops.
Each block is one byte (8 bits), each address is 4 bytes (32 bits).
IPv4 provides over 4 billion unique addresses, however, with over 7 billion people and countless devices per person, a solution was needed.
IPv6
Internet Protocol version 6 is represented as 8 blocks of 4 hexadecimal digits, separated by colons.
Each block is 2 bytes (16 bits), each address is 16 bytes (128 bits).
IPv6 could provide over one billion unique addresses for every person on the planet.
Media access control (MAC) address
A MAC (Media Access Control) address is a unique identifier given to devices which communicate over a local area network (LAN).
MAC addresses are static, they can never change.
MAC addresses make it possible for switches to efficiently forward data to the intended recipient.
Any device that contains a Network Interface Card (NIC) has a MAC address assigned during manufacturing.
A device connecting to a local network already has a MAC address, if it moves to a different network then the MAC address will stay the same.
Packet switching
Packet switching is the process of breaking data down into packets, sending them across the Internet to another computer, and then re-assembling the data.
The file is broken down into data packets of 512 bytes.
Each packet is given a header containing: the IP address it is going to, the IP address it has come from, the sequence number of the packet, the number of packets in the whole communication and error checking data.
Moving data packets
Each data packet contains the same number of bytes.
The packets may flow through the internet via different routes.
The packets may not arrive in the correct order so each packet is marked with a sequence number to be reassembled.
The recipient computer reorders the packets into the correct order.
Each packet is checked for errors.
Corrupt packets are requested to be resent.
Points on a network diagram are called nodes.
Routers are any node that can route packets from one place to another.
Wireless mesh networks
Only one node requires a wired internet connection - no other cabling or infrastructure is required.
The more nodes that use the network, the more routes there are for data to travel through.
A node within broadcast distance of three other nodes will have triple the standard bandwidth.
As the distance between two nodes is halved, signal strength becomes 4 times stronger.
Bluetooth
Bluetooth is a wireless method of connecting devices over a short distance. It uses radio waves at 2.4GHz. devices are typically within 10 metres of each other. devices need to be paired to connect them.
Bluetooth pairing
A persistent link is made between the two devices.
A device can ask for a passkey in order to pair - this gives it an extra layer of security.
They only need to be entered once and will be remembered.
When a paired device is close enough to communicate it will say that it is connected.
This means data can be communicated between them.
Wi-fi standards
There are many different WiFi standards which operate at different speeds. For example:
802.11g operates at 54Mb/s.
802.11n operates at 600Mb/s.
802.11ac operates at 3.2Gb/s.
By creating devices which use the same standards, we can guarantee that devices from different manufacturers will be compatible.
Frequency channels - 2.4GHz
To maximise the amount of data we can send, we subdivide the frequency bands into smaller channels.
There are 13 channels in the 2.4 GHz frequency band.
Only three of these channels do not interfere with each other.
This means that the 2.4 GHz range is not effective at supporting many networks.
Frequency channels - 5GHz
There are 24 non-overlapping channels in the 5 GHz band.
This makes the 5 GHz band much more effective for supporting a high number of networks.
2.4GHz vs 5GHz frequency
2.4GHz has a long range and better reliability through walls and obstructions.
However it is slower than 5GHz wi-fi and is more crowded so more susceptible to interference.
5GHz has faster transfer speeds than 2.4GHz and is less susceptible to interference.
However it has less range and worse reliability through walls and obstructions.
Intercepting data
Data that is transmitted over a network can be intercepted. any intercepted data can be understood unless measures are taken to prevent It from being intercepted. these measures are known as encryption.
Encryption
Encryption is the encoding of data so that It can be no longer be easily understood.
Encryption terminology
plaintext - the original message to be encrypted.
cipher text - the encrypted message.
key - a sequence of numbers used to encrypt or decrypt, often data using mathematical formula.
encryption algorithm - the formula for encrypting the plaintext.
Encryption techniques
private key (symmetric technique) - a single key is used to encrypt and decrypt the plaintext and must be given to the recipient of the message to decrypt the data.
public key (asymmetric technique) - two keys are used - one (public key) to encrypt and one (private key) to decrypt the message. this is more secure as you have to send or reveal your decryption key.
Caesar shift cipher
Each letter is replaced by a letter n positions further on in the alphabet. This is an example of symmetric encryption.
Wireless equivalent privacy (WEP)
WEP is the weakest protection of all.
WEP simply needs a password to join the network.
No data is encrypted, so it can be easily intercepted.
Wi-fi protected access
WPA also uses a password to join the network.
WPA also uses encryption to scramble the data being sent:
This means that only devices with the correct key can decode the data.
WPA is much stronger than WEP.
Wireless equivalent privacy v2
WPA2 is the successor of WPA.
WPA2 uses a stronger encryption algorithm to prevent unauthorised parties from accessing the encrypted data.
