protocolversion

protocolVersion is a numeric or string identifier that denotes the specific version of a communication protocol used by a software component. It is commonly exchanged during handshake or included in protocol metadata to inform the other party about the message formats and feature set that should be applied.

Its primary purpose is to enable compatibility checks and negotiation between communicating parties. When both sides indicate support for a shared protocolVersion, the connection proceeds with compatible rules; if there is no overlap, the peers may reject the connection or fall back to a restricted mode.

Common contexts include TLS, where the protocolVersion indicates versions such as TLS 1.0, 1.2, and 1.3; SSH, which uses a protocol version during the initial handshake; and various internet protocols like HTTP, whose version is reflected in the request line (for example HTTP/1.1 or HTTP/2) and in negotiation mechanisms such as ALPN. In many RPC and data formats, a protocolVersion field is carried in messages to ensure that the receiver can parse and handle the payload correctly.

Versioning schemes vary; some use a simple numeric sequence, others adopt semantic versioning with major versions signaling breaking changes and minor versions adding compatibility or features. Changes typically require deprecation notices and migration paths, as older protocolVersions may be disabled or rejected in newer software to maintain security and interoperability.