Glossary · Change, versions and configuration
Protocol version
In systems engineering, a protocol version is the version of the communication rules used between systems. It identifies which message structure, sequence, timing and error-handling rules apply to an exchange.
- Data and interfaces
- Systems engineering
In one sentence
The protocol version identifies which communication rules two systems use, separately from the data model and behavior versions.
Example
An AGV fleet manager and a door controller negotiate protocol version 2 at connection setup; if the door only supports version 1, the fleet manager refuses to route vehicles through that door.
How it applies
- Integrated systems: Keep the protocol version separate from the data model version and the behavior version. Each can change independently.
- Evidence: Integration tests should record the protocol versions of both peers. A test passed with version 1 says nothing about version 2.
- Machine safety: Define what happens on a version mismatch: refuse the connection, fall back to a supported version or enter a defined safe state.
- Technical documentation: List supported protocol versions in interface documents and release notes, and state the mismatch behavior.
Protocol version vs. behavior version
A protocol version change alters how messages are exchanged. A behavior version change alters what a system does in response. Both peers can agree on the protocol version and still behave differently, so compatibility checks need both.