2.1 Types and methods of data transmission

What is in the header of a packet

• The IP addresses (of the source and receiver)

• The sequence number of the packet

• The packet size

What is in the payload of a packet

The data in the packets (usually around 64KiB)

What is in the trailer of the packet

• An identification method to know that it is the end of the packet

• A form of error checking (usually a CRC which stores the number of one bits as a hex)

What is packet switching

The process where the data sent is:

1. split into packets

2. The packets are sent through different routes

3. The packets that arrive out of order are reordered

What does a USB consist of

• A red 5v wire

• Two data wires (white for + green for -)

• A black ground wire

How is data transmitted in a USB

In serial data with either Half or full-duplex transmission

What are benefits and drawbacks of USB

Benefits	Drawbacks
Plugged in devices are automatically detected and drivers are automatically loaded	Only supports a maximum cable length of 5m. If longer it must have a USB hub
Connections only fit in one way meaning connections cannot be made incorrectly	Despite being backwards compatible, new computers may not support old standards.
It can support various transmission rates (1-5 Mbps to 5 Gbps)	Even the latest versions have slow data transfer rates compared to other methods like ethernet
You don’t need external power supplies
It notifies the transmitter to re-send data if necessary creating error free transmission
It is backward compatible