satcat5::ptp::Measurement Struct Reference

Detailed Description

Timestamps and metadata for a two-way time-transfer handshake.

The Precision Time Protocol (PTP / IEEE-1588-2019) defines several variations on the two-way time-transfer handshake. The process is illustrated in Section 11.3 Figure 41 (leader-follower) and in Section 11.4 Figure 42 (peer-to-peer). In both cases, each complete measurement requires four timestamps:

• t1 = Tx time of 1st message (A to B, measured in A's clock)
• t2 = Rx time of 1st message (A to B, measured in B's clock)
• t3 = Tx time of 2nd message (B to A, measured in B's clock)
• t4 = Rx time of 2nd message (B to A, measured in A's clock)

The Measurement class holds the four timestamps of a given measurement, plus additional metadata such as sequence-ID used to match packets to a given exchange.

See also

MeasurementCache

Definition at line 37 of file ptp_measurement.h.

#include <ptp_measurement.h>

Collaboration diagram for satcat5::ptp::Measurement:

Public Member Functions
	Measurement (const Measurement &t)=default
Measurement &	operator= (const Measurement &t)=default
bool	done () const
	Is this measurement completed? (i.e., T1/T2/T3/T4 all known)
void	log_to (satcat5::log::LogBuffer &wr) const
	Write all four timestamps to the log.
bool	match (const satcat5::ptp::Header &hdr, const satcat5::ptp::PortId &port) const
	Check if an incoming message matches this exchange. More...
satcat5::ptp::Time	mean_path_delay () const
	Calculate PTP "meanPathDelay". More...
satcat5::ptp::Time	mean_link_delay () const
	Calculate PTP "meanLinkDelay". More...
satcat5::ptp::Time	offset_from_master () const
	Calculate PTP "offsetFromMaster". More...
void	reset (const satcat5::ptp::Header &hdr)
	Reset this data structure for immediate reuse. More...

Public Attributes
satcat5::ptp::Header	ref
	Reference header is copied from the initiating PTP message (i.e., SYNC or PDELAY_REQ) and used to match later messages.
satcat5::ptp::Time	t1
	Timestamp T1 (A to B / Tx)
satcat5::ptp::Time	t2
	Timestamp T2 (A to B / Rx)
satcat5::ptp::Time	t3
	Timestamp T3 (B to A / Tx)
satcat5::ptp::Time	t4
	Timestamp T4 (B to A / Rx)

Member Function Documentation

match()

bool Measurement::match	(	const satcat5::ptp::Header &	hdr,
		const satcat5::ptp::PortId &	port
	)		const

Check if an incoming message matches this exchange.

(i.e., Matching sequence-ID, sdo_id, etc.)

Definition at line 32 of file ptp_measurement.cc.

mean_link_delay()

Time Measurement::mean_link_delay

(

)

const

Calculate PTP "meanLinkDelay".

Calculate derived clock parameters using the recommended methods defined in IEEE 1588-2019 Section 11.

Definition at line 46 of file ptp_measurement.cc.

mean_path_delay()

Time Measurement::mean_path_delay

(

)

const

Calculate PTP "meanPathDelay".

Calculate derived clock parameters using the recommended methods defined in IEEE 1588-2019 Section 11.

Definition at line 41 of file ptp_measurement.cc.

offset_from_master()

Time Measurement::offset_from_master

(

)

const

Calculate PTP "offsetFromMaster".

Calculate derived clock parameters using the recommended methods defined in IEEE 1588-2019 Section 11.

Definition at line 51 of file ptp_measurement.cc.

reset()

void Measurement::reset

(

const satcat5::ptp::Header &

hdr

)

Reset this data structure for immediate reuse.

Reset (overwrite) the current measurement state, saving the header of the initiating SYNC or PDELAY_REQ message.

Definition at line 56 of file ptp_measurement.cc.

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The documentation for this struct was generated from the following files:

• ptp_measurement.h
• ptp_measurement.cc