This key facts covers What is a Packet? within Packet Switching for GCSE Computer Science. Revise Packet Switching in Networks for GCSE Computer Science with 15 exam-style questions and 18 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 11 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 11
Practice
15 questions
Recall
18 flashcards
What is a Packet?
Structure of a Network Packet:
Each packet contains three parts: Header, Payload (Data), and Trailer.
1. Packet Header:
- Source IP address: Where packet came from
- Destination IP address: Where packet is going
- Packet number: Sequence number for reassembly (e.g., packet 3 of 10)
- Protocol information: TCP/UDP, etc.
- Time to Live (TTL): Prevents packets looping forever
2. Payload (Data):
- Actual data: The message/file content being transmitted
- Size: Typically 500-1500 bytes per packet
- Fragment of whole: Each packet carries small piece of total data
3. Packet Trailer (Footer):
- Error checking: Checksum or CRC (Cyclic Redundancy Check)
- Detects corruption: Identifies if packet was damaged during transmission
- Validation: Recipient can verify data arrived correctly