Enter Title

Data packets

100

Identify the three parts of a data packet

Head, trailer, payload

200

Identify three things contained in the header

IP address of the sender

IP address of the receiver 

Packet number / order

300

Why does data need to be broken down into packets to be transmitted?

Data such as images and videos can be too large to transfer, this will take a long time to transfer. Breaking down into packets will ensure data can be transferred faster. 

Methods of transmission

100

Data transferred in only one direction

Simplex

200

Describe half duplex / serial data transfer (4 marks- 4 points) 

Data in both directions

Not at the same time

One bit at a time

Down a single wire

300

Identify one advantage and one disadvantage of parallel data transmission

+ Quicker transmission

- Increased chance of data being skewed

- Multiple wires therefore more expensive than serial data transmission

Error checking

100

Identify three methods of error checking

Parity check

Checksum

Checkdigit

Echo check

ARQ

200

Which of the following bytes have been transmitted incorrectly if we were using a parity check and why?

11110000

10101110

11110011

10101110

Uses an odd parity, the other two bytes use an even parity

300

A type of error detection method that uses acknowledgement and timeout to see if data has arrived correctly after transmission

ARQ

Encryption

100

Identify the name given to data before encryption

Plain text

200

Describe the difference between symmetric and asymmetric encryption

Symmetric- uses the same key to encrypt and decrypt data

Asymmetric- uses two different keys to encrypt and decrypt data. 

300

Describe the process for symmetric encryption- 3 points

Plain text is encrypted into cipher text using an encryption key

The cipher text and the encryption key are sent separately to the receiving device.

The same key is then used to decrypt the cipher text back into its plain text form.