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PTP4l(8) System Manager's Manual PTP4l(8)

NAME

ptp4l - PTP Boundary/Ordinary/Transparent Clock

SYNOPSIS

ptp4l [ -AEP246HSLmqsv ] [ -f config ] [ -p phc-device ] [ -l print-level ] [ -i interface ] [ long-options ] ...

DESCRIPTION

ptp4l is an implementation of the Precision Time Protocol (PTP) according to IEEE standard 1588 for Linux. It implements Boundary Clock (BC), Ordinary Clock (OC), and Transparent Clock (TC).

OPTIONS

Select the delay mechanism automatically. Start with E2E and switch to P2P when a peer delay request is received.
Select the delay request-response (E2E) mechanism. This is the default mechanism. All clocks on single PTP communication path must use the same mechanism. A warning will be printed when a peer delay request is received on port using the E2E mechanism.
Select the peer delay (P2P) mechanism. A warning will be printed when a delay request is received on port using the P2P mechanism.
-2
Select the IEEE 802.3 network transport.
-4
Select the UDP IPv4 network transport. This is the default transport.
-6
Select the UDP IPv6 network transport.
Select the hardware time stamping. All ports specified by the -i option and in the configuration file must be attached to the same PTP hardware clock (PHC). This is the default time stamping.
Select the software time stamping.
Select the legacy hardware time stamping.
Read configuration from the specified file. No configuration file is read by default.
Specify a PTP port, it may be used multiple times. At least one port must be specified by this option or in the configuration file.
(This option is deprecated.) Before Linux kernel v3.5 there was no way to discover the PHC device associated with a network interface. This option specifies the PHC device (e.g. /dev/ptp0) to be used when running on legacy kernels.
Enable the slaveOnly mode.
Set the maximum syslog level of messages which should be printed or sent to the system logger. The default is 6 (LOG_INFO).
Print messages to the standard output.
Don't send messages to the system logger.
Prints the software version and exits.
Display a help message.

LONG OPTIONS

Each and every configuration file option (see below) may also appear as a "long" style command line argument. For example, the slaveOnly option may be set using either of these two forms.

--slaveOnly 1 --slaveOnly=1

Option values given on the command line override values in the global section of the configuration file.

CONFIGURATION FILE

The configuration file is divided into sections. Each section starts with a line containing its name enclosed in brackets and it follows with settings. Each setting is placed on a separate line, it contains the name of the option and the value separated by whitespace characters. Empty lines and lines starting with # are ignored.

There are three different section types.

1.
The global section (indicated as [global]) sets the program options, clock options and default port options. Other sections are port specific sections and they override the default port options.
2.
Port sections give the name of the configured port (e.g. [eth0]). Ports specified in the configuration file don't need to be specified by the -i option. An empty port section can be used to replace the command line option.
3.
Tables for configuring unicast discovery begin with [unicast_master_table].

See UNICAST DISCOVERY OPTIONS, below.

PORT OPTIONS

The time difference in nanoseconds of the transmit and receive paths. This value should be positive when the master-to-slave propagation time is longer and negative when the slave-to-master time is longer. The default is 0 nanoseconds.
The mean time interval between Announce messages. A shorter interval makes ptp4l react faster to the changes in the master-slave hierarchy. The interval should be the same in the whole domain. It's specified as a power of two in seconds. The default is 1 (2 seconds).
The mean time interval between Sync messages. A shorter interval may improve accuracy of the local clock. It's specified as a power of two in seconds. The default is 0 (1 second).
The minimum permitted mean time interval between Delay_Req messages. A shorter interval makes ptp4l react faster to the changes in the path delay. It's specified as a power of two in seconds. The default is 0 (1 second).
The minimum permitted mean time interval between Pdelay_Req messages. It's specified as a power of two in seconds. The default is 0 (1 second).
The number of missed Announce messages before the last Announce messages expires. The default is 3.
The number of sync/follow up messages that may go missing before triggering a Best Master Clock election. This option is used for running in gPTP mode according to the 802.1AS-2011 standard. Setting this option to zero will disable the sync message timeout. The default is 0 or disabled.
The transport specific field. Must be in the range 0 to 255. The default is 0.
By default, incoming messages are dropped if their transportSpecific field does not match the configured value. However, many of transports specified in the 1588 standard mandate ignoring this field. Moreover, some equipment is known to set the reserved bits. Configuring this option as 1 causes this field to be ignored completely on receive. The default is 0.
Enable the mechanism used to trace the route of the Announce messages. The default is 0 (disabled).
Include the 802.1AS data in the Follow_Up messages if enabled. The default is 0 (disabled).
The time in seconds between the detection of a port's fault and the fault being reset. This value is expressed as a power of two. Setting this value to -128 or to the special key word "ASAP" will let the fault be reset immediately. The default is 4 (16 seconds).
The time in seconds between the detection of a peer network misconfiguration and the fault being reset. The port is disabled for the duration of the interval. The value is in seconds and the special key word ASAP will let the fault be reset immediately. The default is 16 seconds.
Select the delay mechanism. Possible values are E2E, P2P and Auto. The default is E2E.
Enables the "hybrid" delay mechanism from the draft Enterprise Profile. When enabled, ports in the slave state send their delay request messages to the unicast address taken from the master's announce message. Ports in the master state will reply to unicast delay requests using unicast delay responses. This option has no effect if the delay_mechanism is set to P2P. The default is 0 (disabled).
Some unicast mode profiles insist that no multicast message are ever transmitted. Setting this option inhibits multicast transmission. The default is 0 (mutlicast enabled).
Enables the NetSync Monitor (NSM) protocol. The NSM protocol allows a station to measure how well another node is synchronized. The monitor sends a unicast delay request to the node, which replies unconditionally with unicast delay response, sync, and follow up messages. If the monitor is synchronized to the GM, it can use the time stamps in the message to estimate the node's offset. This option requires that the 'hybrid_e2e' option be enabled as well. The default is 0 (disabled).
When enabled, this option allows the port to grant unicast message contracts. Incoming requests for will be granted limited only by the amount of memory available. The default is 0 (disabled).
When set to a positive integer, this option specifies the table id to be used for unicast discovery. Each table lives in its own section and has a unique, positive numerical ID. Entries in the table are a pair of transport type and protocol address. Tables may not be shared between ports, but nothing prevents table entries from appearing in more than table. The default is 0 (unicast discovery disabled).
The service time in seconds to be requested during unicast discovery. Note that the remote node is free to grant a different duration. The default is 3600 seconds or one hour.
The MAC address to which PTP messages should be sent. Relevant only with L2 transport. The default is 01:1B:19:00:00:00.
The MAC address to which peer delay messages should be sent. Relevant only with L2 transport. The default is 01:80:C2:00:00:0E.
Select the network transport. Possible values are UDPv4, UDPv6 and L2. The default is UDPv4.
Upper limit for peer delay in nanoseconds. If the estimated peer delay is greater than this value the port is marked as not 802.1AS capable.
Setting this option to one (1) prevents the port from entering the SLAVE state. In addition, the local clock will ignore Announce messages received on this port. This option's intended use is to support the Telecom Profiles according to ITU-T G.8265.1, G.8275.1, and G.8275.2. The default value is zero or false.
The Telecom Profiles (ITU-T G.8275.1 and G.8275.2) specify an alternate Best Master Clock Algorithm (BMCA) with a unique data set comparison algorithm. The value of this option is associated with Announce messages arriving on a particular port and is used as a tie breaker whenever clockClass, clockAccuracy, offsetScaledLogVariance, and priority2 are equal. This option is only used when "dataset_comparison" is set to "telecom". The default value is 128.

Warning: the BMCA is guaranteed to produce a spanning tree (that is, a timing network without loops) only when using the default values of G.8275.defaultDS.localPriority and G.8275.portDS.localPriority. Careful network engineering is needed when using non-default values.

Lower limit for peer delay in nanoseconds. If the estimated peer delay is smaller than this value the port is marked as not 802.1AS capable.
Select the time stamp processing mode used to calculate offset and delay. Possible values are filter, raw, filter_weight, raw_weight. Raw modes perform well when the rate of sync messages (logSyncInterval) is similar to the rate of delay messages (logMinDelayReqInterval or logMinPdelayReqInterval). Weighting is useful with larger network jitters (e.g. software time stamping). The default is filter.
Select the algorithm used to filter the measured delay and peer delay. Possible values are moving_average and moving_median. The default is moving_median.
The length of the delay filter in samples. The default is 10.
Specifies the difference in nanoseconds between the actual transmission time at the reference plane and the reported transmit time stamp. This value will be added to egress time stamps obtained from the hardware. The default is 0.
Specifies the difference in nanoseconds between the reported receive time stamp and the actual reception time at reference plane. This value will be subtracted from ingress time stamps obtained from the hardware. The default is 0.
When running as a boundary clock (that is, when more than one network interface is configured), ptp4l performs a sanity check to make sure that all of the ports share the same hardware clock device. This option allows ptp4l to work as a boundary clock using "just a bunch of devices" that are not synchronized to each other. For this mode, the collection of clocks must be synchronized by an external program, for example phc2sys(8) in "automatic" mode. The default is 0 (disabled).
Specifies the Time to live (TTL) value for IPv4 multicast messages and the hop limit for IPv6 multicast messages. This option is only relevant with the IPv4 and IPv6 UDP transports. The default is 1 to restrict the messages sent by ptp4l to the same subnet.

PROGRAM AND CLOCK OPTIONS

Enable two-step mode for sync messages. One-step mode can be used only with hardware time stamping. The default is 1 (enabled).
The local clock is a slave-only clock if enabled. This option is only for use with 1588 clocks and should not be enabled for 802.1AS clocks. The default is 0 (disabled).
If this option is enabled, then the local clock is able to become grand master. This is only for use with 802.1AS clocks and has no effect on 1588 clocks. The default is 1 (enabled).
The priority1 attribute of the local clock. It is used in the best master selection algorithm, lower values take precedence. Must be in the range 0 to 255. The default is 128.
The priority2 attribute of the local clock. It is used in the best master selection algorithm, lower values take precedence. Must be in the range 0 to 255. The default is 128.
The clockClass attribute of the local clock. It denotes the traceability of the time distributed by the grandmaster clock. The default is 248.
The clockAccuracy attribute of the local clock. It is used in the best master selection algorithm. The default is 0xFE.
The offsetScaledLogVariance attribute of the local clock. It characterizes the stability of the clock. The default is 0xFFFF.
The Telecom Profiles (ITU-T G.8275.1 and G.8275.2) specify an alternate Best Master Clock Algorithm (BMCA) with a unique data set comparison algorithm. The value of this option is associated with the local clock and is used as a tie breaker whenever clockClass, clockAccuracy, offsetScaledLogVariance, and priority2 are equal. This option is only used when "dataset_comparison" is set to "telecom". The default value is 128.

Warning: the BMCA is guaranteed to produce a spanning tree (that is, a timing network without loops) only when using the default values of G.8275.defaultDS.localPriority and G.8275.portDS.localPriority. Careful network engineering is needed when using non-default values.

The domain attribute of the local clock. The default is 0.
The current offset between TAI and UTC. The default is 37.
Don't adjust the local clock if enabled. The default is 0 (disabled).
The time interval over which is estimated the ratio of the local and peer clock frequencies. It is specified as a power of two in seconds. The default is 1 (2 seconds).
Treat one-step responses as two-step if enabled. It is used to work around buggy 802.1AS switches. The default is 0 (disabled).
When running as a Transparent Clock, increment the "stepsRemoved" field of Announce messages that pass through the switch. Enabling this option ensures that PTP message loops never form, provided the switches all implement this option together with the BMCA.
The number of milliseconds to poll waiting for the tx time stamp from the kernel when a message has recently been sent. The default is 1.
Because of packet reordering that can occur in the network, in the hardware, or in the networking stack, a follow up message can appear to arrive in the application before the matching sync message. As this is a normal occurrence, and the sequenceID message field ensures proper matching, the ptp4l program accepts out of order packets. This option adds an additional check using the software time stamps from the networking stack to verify that the sync message did arrive first. This option is only useful if you do not trust the sequence IDs generated by the master. The default is 0 (disabled).
The servo which is used to synchronize the local clock. Valid values are "pi" for a PI controller, "linreg" for an adaptive controller using linear regression, "ntpshm" for the NTP SHM reference clock to allow another process to synchronize the local clock (the SHM segment number is set to the domain number), and "nullf" for a servo that always dials frequency offset zero (for use in SyncE nodes). The default is "pi."
Specifies the kind of PTP clock. Valid values are "OC" for ordinary clock, "BC" for boundary clock, "P2P_TC" for peer to peer transparent clock, and "E2E_TC" for end to end transparent clock. An multi-port ordinary clock will automatically be configured as a boundary clock. The default is "OC".
The proportional constant of the PI controller. When set to 0.0, the proportional constant will be set by the following formula from the current sync interval. The default is 0.0.

kp = min(kp_scale * sync^kp_exponent, kp_norm_max / sync)

The integral constant of the PI controller. When set to 0.0, the integral constant will be set by the following formula from the current sync interval. The default is 0.0.

ki = min(ki_scale * sync^ki_exponent, ki_norm_max / sync)

The kp_scale constant in the formula used to set the proportional constant of the PI controller from the sync interval. When set to 0.0, the value will be selected from 0.7 and 0.1 for the hardware and software time stamping respectively. The default is 0.0.
The kp_exponent constant in the formula used to set the proportional constant of the PI controller from the sync interval. The default is -0.3.
The kp_norm_max constant in the formula used to set the proportional constant of the PI controller from the sync interval. The default is 0.7
The ki_scale constant in the formula used to set the integral constant of the PI controller from the sync interval. When set to 0.0, the value will be selected from 0.3 and 0.001 for the hardware and software time stamping respectively. The default is 0.0.
The ki_exponent constant in the formula used to set the integral constant of the PI controller from the sync interval. The default is 0.4.
The ki_norm_max constant in the formula used to set the integral constant of the PI controller from the sync interval. The default is 0.3.
The maximum offset the servo will correct by changing the clock frequency instead of stepping the clock. When set to 0.0, the servo will never step the clock except on start. It's specified in seconds. The default is 0.0. This option used to be called pi_offset_const.
The maximum offset the servo will correct by changing the clock frequency instead of stepping the clock. This is only applied on the first update. It's specified in seconds. When set to 0.0, the servo won't step the clock on start. The default is 0.00002 (20 microseconds). This option used to be called pi_f_offset_const.
The maximum allowed frequency adjustment of the clock in parts per billion (ppb). This is an additional limit to the maximum allowed by the hardware. When set to 0, the hardware limit will be used. The default is 900000000 (90%). This option used to be called pi_max_frequency.
The maximum allowed frequency offset between uncorrected clock and the system monotonic clock in parts per billion (ppb). This is used as a sanity check of the synchronized clock. When a larger offset is measured, a warning message will be printed and the servo will be reset. When set to 0, the sanity check is disabled. The default is 200000000 (20%).
The initial path delay of the clock in nanoseconds used for synchronization of the clock before the delay is measured using the E2E or P2P delay mechanism. If set to 0, the clock will not be updated until the delay is measured. The default is 0.
The number of the SHM segment used by ntpshm servo. The default is 0.
Specifies the desired scope for the IPv6 multicast messages. This will be used as the second byte of the primary address. This option is only relevant with IPv6 transport. See RFC 4291. The default is 0x0E for the global scope.
Specifies the address of the UNIX domain socket for receiving local management messages. The default is /var/run/ptp4l.
Defines the Differentiated Services Codepoint (DSCP) to be used for PTP event messages. Must be a value between 0 and 63. There are several media streaming standards out there that require specific values for this option. For example 46 (EF PHB) in AES67 or 48 (CS6 PHB) in RAVENNA. The default is 0.
Defines the Differentiated Services Codepoint (DSCP) to be used for PTP general messages. Must be a value between 0 and 63. There are several media streaming standards out there that recommend specific values for this option. For example 34 (AF41 PHB) in AES67 or 46 (EF PHB) in RAVENNA. The default is 0.
Specifies the method to be used when comparing data sets during the Best Master Clock Algorithm. The possible values are "ieee1588" and "G.8275.x". The default is "ieee1588".
The maximum logging level of messages which should be printed. The default is 6 (LOG_INFO).
The tag which is added to all messages printed to the standard output or system log. The default is an empty string (which cannot be set in the configuration file as the option requires an argument).
Print messages to the standard output if enabled. The default is 0 (disabled).
Print messages to the system log if enabled. The default is 1 (enabled).
The time interval in which are printed summary statistics of the clock. It is specified as a power of two in seconds. The statistics include offset root mean square (RMS), maximum absolute offset, frequency offset mean and standard deviation, and path delay mean and standard deviation. The units are nanoseconds and parts per billion (ppb). If there is only one clock update in the interval, the sample will be printed instead of the statistics. The messages are printed at the LOG_INFO level. The default is 0 (1 second).
The time stamping method. The allowed values are hardware, software and legacy. The default is hardware.
The product description string. Allowed values must be of the form manufacturerName;modelNumber;instanceIdentifier and contain at most 64 utf8 symbols. The default is ";;".
The revision description string which contains the revisions for node hardware (HW), firmware (FW), and software (SW). Allowed values are of the form HW;FW;SW and contain at most 32 utf8 symbols. The default is an ";;".
The user description string. Allowed values are of the form name;location and contain at most 128 utf8 symbols. The default is an empty string.
The manufacturer id which should be an OUI owned by the manufacturer. The default is 00:00:00.
When a leap second is announced, let the kernel apply it by stepping the clock instead of correcting the one-second offset with servo, which would correct the one-second offset slowly by changing the clock frequency (unless the step_threshold option is set to correct such offset by stepping). Relevant only with software time stamping. The default is 1 (enabled).
The time source is a single byte code that gives an idea of the kind of local clock in use. The value is purely informational, having no effect on the outcome of the Best Master Clock algorithm, and is advertised when the clock becomes grand master.

UNICAST DISCOVERY OPTIONS

Each table must begin with a unique, positive table ID. The port that claims a given table does so by including the ID as the value of its 'unicast_master_table' option.
This option configures the time to wait between unicast negotiation attempts. It is specified as a power of two in seconds. The default is 0 (1 second).
This option specifies the unicast address of the peer for use with the peer to peer delay mechanism. If specified, the port owning the table will negotiate unicast peer delay responses from the machine at the given remote address, otherwise the port will send multicast peer delay requests.
Each table entry specifies the transport type and network address of a potential remote master. If multiple masters are specified, then unicast negotiation will be performed with each if them.

TIME SCALE USAGE

ptp4l as domain master either uses PTP or UTC time scale depending on time stamping mode. In software and legacy time stamping modes it announces Arbitrary time scale mode, which is effectively UTC here, in hardware time stamping mode it announces use of PTP time scale.

When ptp4l is the domain master using hardware time stamping, it is up to phc2sys to maintain the correct offset between UTC and PTP times. See phc2sys(8) manual page for more details.

SEE ALSO

pmc(8), phc2sys(8)

April 2018 linuxptp