Data Transmission and Packet Switching

Data Transmission

• Data is broken into packets for transmission.
• A packet consists of a header, payload, and trailer.

Packet Structure

• Header: Contains control information such as destination address, packet number, originator's address, checksum, flags, and protocol.
• Payload: The actual data being transmitted.
• Trailer: Indicates the end of the packet and includes error checking information like Cyclic Redundancy Check (CRC).

Key Terms

• Data Packet: A small part of a message transmitted over a network.
• Packet Header: Contains IP addresses of sender and receiver, and packet number.
• Packet Trailer: Indicates the end of the packet and includes CRC error check.
• Payload: Actual data carried in the packet.
• Cyclic Redundancy Check (CRC): Error checking method by summing 1-bits in payload and storing the total in the trailer.
• Node: Stages in a network that can receive and transmit data packets.
• Packet Switching: A method where messages are broken into packets and sent independently.
• Router: A device that moves data packets between networks.
• Real-Time Streaming: Data transmission for live events.
• Hopping/Hop Number: A number in the packet header to stop packets from endlessly looping.

Packet Switching

• Data is broken down into packets.
• Each packet can take a different route.
• Routers control the route.
• Packets may arrive out of order and are reordered upon arrival.

Packet Switching Benefits:

1. No need to tie up a single communication line.
2. Overcome failed/busy lines by re-routing.
3. Easy to expand package usage.
4. High data transmission rate.

Packet Switching Drawbacks:

1. Packets can be lost and need re-sending.
2. More prone to errors with real-time streaming.
3. Delay at destination for re-ordering.
4. Packets may get lost bouncing between routers.

Hopping

• A hop number is added to the header of each packet and decremented at each router.
• Packets are deleted if hop number reaches zero before reaching destination.