Implementations of the 2019 revision, known informally as PTP v2.1, should be backwards compatible with implementations of the 2008 revision (v2.0) but to assure continued interoperability with intolerant peer devices the protocol version must be specified to use new features, such as the COMMUNICATION_CAPABILITIES TLV:
[ptp]
ptp_version 2.1See the ptp_version option in Configuration Options.