Cambridge O Level Computer Science · Syllabus 2210 · Data Transmission
Payload
What is Payload?
The payload is the part of a packet that holds the data being transmitted; it carries only part of the original data and does not contain the addressing information.
This definition is part of the Data Transmission chapter in Cambridge O Level Computer Science.
Payload in context
A packet of data contains a packet header, a payload and a trailer. The packet header includes the destination address, the packet number and the originator's address. The payload is the part of the data being transmitted that this packet is carrying. The trailer is the information at the end of the packet; depending on the protocol in use it may contain error-checking information and a marker showing that the end of the packet has been reached.
Common mistakes with Payload
- Trap. Do not put any of these in the payload. The payload holds part of the data being transmitted and nothing else.
Examiner tips on Payload
- Read the verbs, not just the nouns. Topic 2 is dominated by describe and explain. A list of nouns — “header, payload, trailer” — answers identify, not describe. A described process needs the steps in the right order, and an explained choice needs the reason tied back to the scenario you were given.
Questions students ask about Payload
Why is data broken down into packets before it is transmitted across a network?
Splitting data into packets means many users can share the same network instead of one transfer occupying the link from start to finish, means each packet can be routed independently by a router, and means a single damaged packet can be dealt with on its own rather than resending the whole file. Each packet carries a header with the destination address, packet number and originator's address, a payload, and a trailer, so the receiver can reorder and rebuild the original data once every packet has arrived.