What are the parts of a data packet?
Packet header
Payload
Packet trailer
What does the packet header contain?
IP address of sending station and receiving station
Sequence number of packet
Packet size
What does the payload contain?
The actual data
What is the packet trailer for and what does it contain?
A way of identifying the end of the data packet
Contains cyclic redundancy check (CRC) (error check)
What are routers also known as nodes for?
Used to control the path a data packet takes from sending station to receiving station
What is packet switching?
Each packet can take a different route
What are the benefits of packet switching?
No need to tie up a single communication line
Possible to overcome failed, busy or faulty lines by simply re-routing packets
Relatively easy to expand package usage
High data transmission rate is possible
What are the drawbacks of packet switching?
Packets can be lost and need to be re-sent
Does not work well with real-time streaming
delay at the destination whilst the packets are being re-ordered
What is simplex data transmission?
Data can be sent in one direction only
What is half-duplex data transmission?
Data can be sent in both directions, but not simultaneously
What is full-duplex data transmission?
Data can be sent in both directions at the same time
What is serial data transmission?
Data is sent one bit at a time down a single wire/channel
What is parallel data transmission?
Several bits of data are sent down several wires/channels at the same time - each wire/channel transmits each bit
What are the benefits of USB data transmission?
Devices plugged into the computer are automatically detected and device drivers are automatically loaded up
Connections can only fit one way preventing incorrect connections being made
Has become an industry standard
Can support different data transmission rates
No need for external power source since cable supplies +5V power
USB protocol notifies the transmitter to re-transmit data if any errors are detected
Relatively easy to add more USB ports if necessary by using USB hubs
Backward compatible
What are the drawbacks of USB data transmission?
Standard USB only supports a max cable length of 5m
Very early USB standards may not always be supported by later computers
Slow data transfer rate
What are the advantages of later USB models?
Smaller and thinner
More power
Faster and greater data transfer
Backward compatible
What can cause errors during data transmission?
Electrical interference
Packet switching
Skewing of data
What are some ways to check if data has been changed or corrupted following data transmission?
Parity checks
Checksum
Echo checks
What is plaintext?
The original readable data before ecryptio
What is ciphertext?
The encrypted data
