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

-A  Select the delay mechanism automatically. Start with E2E and switch to P2P when a peer delay request is received.

-E  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.

-P  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.

-H  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.

-S  Select the software time stamping.

-L  Select the legacy hardware time stamping.

-f config
    Read configuration from the specified file. No configuration file is read by default.

-i interface
    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.

-p phc-device
    (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.

-s  Enable the slaveOnly mode.

-l print-level
    Set the maximum syslog level of messages which should be printed or sent to the system logger. The default is 6 (LOG_INFO).

-m  Print messages to the standard output.

-q  Don't send messages to the system logger.

-v  Prints the software version and exits.

-h  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

delayAsymmetry
    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.

logAnnounceInterval
    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).

logSyncInterval
    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).

operLogSyncInterval
    The Sync message interval to be requested once the clock enters the SERVO_LOCKED_STABLE state. If the 'msg_interval_request' option is set, then the local slave port will request the remote master to switch to the given message rate via a signaling message containing a Message interval request TLV. This option is specified as a power of two in seconds, and default value is 0 (1 second).

logMinDelayReqInterval
    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).

logMinPdelayReqInterval
    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).

operLogPdelayReqInterval
    The Pdelay Request messages interval to be used once the clock enters the SERVO_LOCKED_STABLE state. If the 'msg_interval_request' option is set, then the local slave port will adopt this rate when the local clock enters the "locked stable" state. This option is specified as a power of two in seconds, and the default value is 0 (1 second).

inhibit_delay_req
    Don't send any delay requests. This will need the asCapable config option to be set to 'true'. This is useful when running as a designated master who does not need to calculate offset from slave. The default is 0 (disabled).

announceReceiptTimeout
    The number of missed Announce messages before the last Announce messages expires. The default is 3.

syncReceiptTimeout
    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.

transportSpecific
    The transport specific field. Must be in the range 0 to 255. The default is 0.

ignore_transport_specific
    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.

path_trace_enabled
    Enable the mechanism used to trace the route of the Announce messages. The default is 0 (disabled).

follow_up_info
    Include the 802.1AS data in the Follow_Up messages if enabled. The default is 0 (disabled).

fault_reset_interval
    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).

fault_badpeernet_interval
    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.

delay_mechanism
    Select the delay mechanism. Possible values are E2E, P2P and Auto. The default is E2E.

hybrid_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).

inhibit_multicast_service
    Some unicast mode profiles insist that no multicast message are ever transmitted. Setting this option inhibits multicast transmission. The default is 0 (mutlicast enabled).

net_sync_monitor
    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).

unicast_listen
    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).

unicast_master_table
    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. The default is 0 (unicast discovery disabled).

unicast_req_duration
    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.

ptp_dst_mac
    The MAC address to which PTP messages should be sent. Relevant only with L2 transport. The default is 01:1B:19:00:00:00.

p2p_dst_mac
    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.

network_transport
    Select the network transport. Possible values are UDPv4, UDPv6 and L2. The default is UDPv4.

neighborPropDelayThresh
    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.

masterOnly
    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.

G.8275.portDS.localPriority
    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.

min_neighbor_prop_delay
    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.

tsproc_mode
    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.

delay_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.

delay_filter_length
    The length of the delay filter in samples. The default is 10.

egressLatency
    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.

ingressLatency
    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.

boundary_clock_jbod
    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).

udp_ttl
    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

twoStepFlag
    Enable two-step mode for sync messages. One-step mode can be used only with hardware time stamping. The default is 1 (enabled).

slaveOnly
    The local clock is a slave-only clock if enabled. The default is 0 (disabled).

socket_priority
    Configure the SO_PRIORITY of sockets. This is to support cases where a user wants to route ptp4l traffic using Linux qdiscs for the purpose of traffic shaping. This option is only available with the IEEE 802.3 transport (the -2 option) and is silently ignored when using the UDP IPv4/6 network transports. Must be in the range of 0 to 15, inclusive. The default is 0.

gmCapable
    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).

priority1
    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.

priority2
    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.

clockClass
    The clockClass attribute of the local clock. It denotes the traceability of the time distributed by the grandmaster clock. The default is 248.

clockAccuracy
    The clockAccuracy attribute of the local clock. It is used in the best master selection algorithm. The default is 0xFE.

clockIdentity
    The clockIdentity attribute of the local clock. The clockIdentity is an 8-octet array and should in this configuration be written in textual form, see default. It should be unique since it is used to identify the specific clock. If default is used or if not set at all, the clockIdentity will be automtically generated. The default is "000000.0000.000000"

offsetScaledLogVariance
    The offsetScaledLogVariance attribute of the local clock. It characterizes the stability of the clock. The default is 0xFFFF.

G.8275.defaultDS.localPriority
    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.

maxStepsRemoved
    When using this option, if the value of stepsRemoved of an Announce message is greater than or equal to the value of maxStepsRemoved the Announce message is not considered in the operation of the BMCA. The default value is 255.

domainNumber
    The domain attribute of the local clock. The default is 0.

utc_offset
    The current offset between TAI and UTC. The default is 37.

free_running
    Don't adjust the local clock if enabled. The default is 0 (disabled).

freq_est_interval
    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).

assume_two_step
    Treat one-step responses as two-step if enabled. It is used to work around buggy 802.1AS switches. The default is 0 (disabled).

tc_spanning_tree
    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.

tx_timestamp_timeout
    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.

check_fup_sync
    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).

clock_servo
    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."

clock_type
    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".

pi_proportional_const
    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)

pi_integral_const
    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)

pi_proportional_scale
    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.

pi_proportional_exponent
    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.

pi_proportional_norm_max
    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

pi_integral_scale
    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.

pi_integral_exponent
    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.

pi_integral_norm_max
    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.

step_threshold
    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.

first_step_threshold
    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.

max_frequency
    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.

sanity_freq_limit
    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%).

initial_delay
    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.

ntpshm_segment
    The number of the SHM segment used by ntpshm servo. The default is 0.

udp6_scope
    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.

uds_address
    Specifies the address of the UNIX domain socket for receiving local management messages. The default is /var/run/ptp4l.

dscp_event
    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.

dscp_general
    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.

dataset_comparison
    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".

logging_level
    The maximum logging level of messages which should be printed. The default is 6 (LOG_INFO).

message_tag
    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).

verbose
    Print messages to the standard output if enabled. The default is 0 (disabled).

use_syslog
    Print messages to the system log if enabled. The default is 1 (enabled).

summary_interval
    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).

time_stamping
    The time stamping method. The allowed values are hardware, software and legacy. The default is hardware.

productDescription
    The product description string. Allowed values must be of the form manufacturerName;modelNumber;instanceIdentifier and contain at most 64 utf8 symbols. The default is ";;".

revisionData
    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 ";;".

userDescription
    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.

manufacturerIdentity
    The manufacturer id which should be an OUI owned by the manufacturer. The default is 00:00:00.

kernel_leap
    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).

timeSource
    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.

hwts_filter
    Select the hardware time stamp filter setting mode. Possible values are normal, check, full. Normal mode set the filters as needed. Check mode only check but do not set. Full mode set the receive filter to mark all packets with hardware time stamp,
     so all applications can get them. The default is normal.

asCapable
    If set to 'true', all the checks which can unset asCapable variable (as described in Section 10.2.4.1 of 802.1AS) are skipped. If set to 'auto', asCapable is initialized to 'false' and will be set to 'true' after the relevant checks have passed. The default value is 'auto'.

BMCA
    This option enables use of static roles for master and slave devices instead of running the best master clock algorithm (BMCA) described in 1588 profile. This is useful when you know the roles of the devices in advance. When set to 'noop', the traditional BMCA algorithm used by 1588 is skipped. masterOnly and slaveOnly will be used to determine master or slave role for the device. In a bridge, slaveOnly (which is a global option) can be set to make all ports assume the slave role. masterOnly (which is a per-port config option) can then be used to set individual ports to take master role. BMCA is used in the Automotive profile to speed up the start time for grand master and slaves. The default value is 'ptp' which runs the BMCA related state machines.

inhibit_announce
    This will disable the timer for announce messages (i.e. FD_MANNO_TIMER) and also the announce message timeout timer (i.e. FD_ANNOUNCE_TIMER). This is used by the Automotive profile as part of switching over to a static BMCA. if this option is enabled, ignore_source_id has to be enabled in the slave because it has no way to identify master identity in Sync and Follow_Up messages. The default is 0 (disabled).

ignore_source_id
    This will disable source port identity checking for Sync and Follow_Up messages. This is useful when the announce messages are disabled in the master and the slave does not have any way to know it's identity. The default is 0 (disabled).

msg_interval_request
    This option, when set, will trigger an adjustment to the Sync and peer delay request message intervals when the clock servo transitions into the SERVO_LOCKED_STABLE state. The Sync interval will be adjusted via the signaling mechanism while the pdelay request interval is simply adjusted locally. The values to use for the new Sync and peer delay request intervals are specified by the operLogSyncInterval and operLogPdelayReqInterval options, respectively. The default value of msg_interval_request is 0 (disabled).

servo_num_offset_values
    The number of offset values considered in order to transition from the SERVO_LOCKED to the SERVO_LOCKED_STABLE state. The transition occurs once the last 'servo_num_offset_values' offsets are all below the 'servo_offset_threshold' value. The default value is 10.

servo_offset_threshold
    The offset threshold used in order to transition from the SERVO_LOCKED to the SERVO_LOCKED_STABLE state. The transition occurs once the last The default value of offset_threshold is 0 (disabled).

slave_event_monitor
    Specifies the address of a UNIX domain socket for slave event monitoring. A local client bound to this address will receive SLAVE_RX_SYNC_TIMING_DATA and SLAVE_DELAY_TIMING_DATA_NP TLVs. The default is the empty string (disabled).

write_phase_mode
    This option enables using the "write phase" feature of a PTP Hardware Clock. If supported by the device, this mode uses the hardware's built in phase offset control instead of frequency offset control. The default value is 0 (disabled).

UNICAST DISCOVERY OPTIONS

table_id
    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.

logQueryInterval
    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).

peer_address
    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.

L2|UDPv4|UDPv6
    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)