Glossary · Requirements and interfaces
Protocol (communication)
In systems engineering, a protocol is a set of technical rules for communication between systems, such as message structure, sequence, addressing, timing and error handling. It governs how data is exchanged, not what the data means.
- Data and interfaces
- Systems engineering
In one sentence
A communication protocol sets the rules for exchanging messages between systems; the data model, not the protocol, defines what the content means.
Example
A robot cell and a conveyor exchange handshake signals over an industrial Ethernet protocol, while a separate data model defines that value 3 in the status field means “blocked”.
How it applies
- Integrated systems: Record the protocol and its protocol version for each interface, together with timing, timeout and error handling rules.
- Machine safety: A standard communication protocol does not make a connection safety-rated. Safety-relevant signals need a safety function design and evidence that covers the communication path.
- Cybersecurity: Protocol choice affects authentication and integrity options. Consider it together with the security zones and conduits of the plant.
- Technical documentation: Name the protocol in interface documents and commissioning instructions, but document meanings, units and ranges in the data model.
Protocol vs. data model
The protocol answers how systems talk: framing, order, acknowledgment, retries. The data model answers what they say: fields, meanings, units, enumerations. Mixing the two in one specification makes it hard to see which change breaks what.