Linux PTP Hardware Clock (PHC) subsystem, and synchronizing the system clock to it. Boundary Clock and Ordinary Clock. IEEE 802.1AS-2011 in the role of end station. Transport over UDP/IPv4, UDP/IPv6, and raw Ethernet (Layer 2 and VLAN).
PTP hardware clock infrastructure for Linux. This patch set introduces support for IEEE 1588 PTP clocks in Linux. Together with the SO_TIMESTAMPING socket options, this presents a standardized method for developing PTP user space programs, synchronizing Linux with external clocks, and using the ancillary features of PTP hardware clocks.
PTP (Precision Time Protocol) •Use cases •Time synchronization among the switches and servers •Debug packet latency issues in the network •ASIC functions •Timestamping Tx/Rx packets •Adjust hardware clock time, e.g., offset, frequency •SAI Interface •Host traps (trap PTP packets)
in short: ptp_kvm.ko # modprobe ptp_kvm # ls /dev/ptp* /dev/ptp0 /dev/ptp_kvm in long: Red Hat Enterprise Linux 7.5 and later provide a virtual PTP hardware clock (PHC), which enables the guests to synchronize to the host with a sub-microsecond accuracy.
PTP hardware clock I PHC are used by hardware engines to timestamp packets. I The PHC must be synchronized. I Described by structptp_clock_info, which embeds operation callbacks: I gettimex64: reports the current time from the hardware clock by ﬁlling a timespec64 structure. I settime64: sets the time on the hardware clock.