Data Transmission By Karl Taylor - created from Mind Map

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Computers connected together are networked

Network Interface Card (NIC)

Methods Of Transmission

Bits

Procedures to prevent corruption

Circuit Switching and Packet Switching

Protocols

One type of network is Wide Area Network (WAN)

One type of network is Local Area Network (LAN)

Differences

One example of this is the internet

Since WAN uses a public communications medium it is easier to intercept messages

Used in places such as schools or wireless connected computers at home

LAN has all the machines close but WAN is more spread out

LAN is probably hard wired using cable or is connected via a wireless system. WAN usually uses a communication system that is not owned by the owners of the computer.

LAN is more secure then WAN as long as its not connetcted to a WAN such as the internet

The internet would use a telecommunications company such as BT

Needed in each computer so that the computer can communicate with other machines and controls the communications

Will use a medium

Network can be used to allow:

If lots of computers are trying to access the same folder then lots of traffic will be made on the network

Communication

Sharing of files

Software

Hardware

E.g. Printer

Will cause bottlenecks and slow down the network

Solutions

Change the way the network is wired together

Store files and networks at different places on the network so that all the data is not coming from one place

May mean that extra hardware is needed

System will be reliant on the ability of the hardware to maintain communications and a compromise is usually made between what is practicable and what speeds are acceptable

By being connected to a cable or a wireless antenna so that messages can be passed,

and to software that can control the whole process (a Network Operating System (NOS))

Serial Data Transmission

Parallel Data Transmission

Simplex Data Transmission

Duplex (Full Duplex) Transmission

Half Duplex

This is when data is sent one bit at a time through a single wire (connection)

Very safe way to transmit data since the data is transmitted 1 by 1 however it is a lot slower than parallel transmission

Data is transmitted using a number of wires. One for each of the bits in the byte

Faster than serial transmission but less safe

This is when data can only be transmitted in one direction.

This is when data can be transmitted in both directions

This is when data can be sent both ways but is only being used to send data one way

The number of bits that can be transmitted in a given period of time is called the bit rate

Bits can be corrupted over transmission

The units its measured in is called baud and the the baud rate is the number of bits that can be transmitted per second.

High bit rates are used for streaming and low bit rates are used for downloads

When streaming if the video starts to freeze then its because the bit rate is not high enough

This may be because more than one device is using the network and lowering the bit rate available

1's can be become 0's and vise versa

Echoing Back

Check Sums

Parity Check

This is when a set of data is sent from one device to another and then when the data reaches the device it is sent back and compared to what was sent to check that the data matches

This when a set of data is sent and the numbers are added together and the answer is sent with the data. When data reaches its destination it is added together to figure out the checksum and the checksum is compared to the answer to ensure the data has not been corrupted

The last bit of data in a byte s reserved as a parity bit. This then works by using the parity check as a test to check if there is an odd or even amount of 1's or 0's

Packets

When data is sent from one machine to another it must first be gathered and put into a bundle of data called packets

They have a standard size

They have a label attached saying what data file it is part of, which packet it is and where its going

There are only two ways of sending packets

Circuit Swithing

Packet Switching

Speed is not an advantage for either

A path between the two machines is first established and then all the packets are sent along the path in order

The path is reserved for the duration of the message and is then shut down

This ties up resources on the network and can be done more efficeintly but the packets will arrive at their destination in the right order

The packets are sent onto the network to follow the most convenient path at that time

When a packet reaches a machine on a network the label is read and if its not destined for that machine then the most suitable path is chosen and the packet is launched down another route

Doesnt tie up resources and is hard to intercept because all the packets travel using diffrient routes

The packets will travel using diffrient routes

When they arrive at the destination they have to be re-ordered before that file of data can be used

Definition: A set of rules