1PTP4l(8)                    System Manager's Manual                   PTP4l(8)
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NAME

6       ptp4l - PTP Boundary/Ordinary/Transparent Clock
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SYNOPSIS

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

15       ptp4l is an implementation of the Precision Time Protocol (PTP) accord‐
16       ing to IEEE standard 1588 for Linux. It implements Boundary Clock (BC),
17       Ordinary Clock (OC), and Transparent Clock (TC).
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OPTIONS

21       -A     Select the delay mechanism automatically.  Start  with  E2E  and
22              switch to P2P when a peer delay request is received.
23
24       -E     Select  the  delay request-response (E2E) mechanism. This is the
25              default mechanism. All clocks on single PTP  communication  path
26              must  use  the  same mechanism. A warning will be printed when a
27              peer delay request is received on port using the E2E mechanism.
28
29       -P     Select the peer delay (P2P) mechanism. A warning will be printed
30              when  a  delay  request is received on port using the P2P mecha‐
31              nism.
32
33       -2     Select the IEEE 802.3 network transport.
34
35       -4     Select the UDP IPv4  network  transport.  This  is  the  default
36              transport.
37
38       -6     Select the UDP IPv6 network transport.
39
40       -H     Select the hardware time stamping. All ports specified by the -i
41              option and in the configuration file must  be  attached  to  the
42              same  PTP  hardware clock (PHC). This is the default time stamp‐
43              ing.
44
45       -S     Select the software time stamping.
46
47       -L     Select the legacy hardware time stamping.
48
49       -f config
50              Read configuration from the  specified  file.  No  configuration
51              file is read by default.
52
53       -i interface
54              Specify  a PTP port, it may be used multiple times. At least one
55              port must be specified by this option or  in  the  configuration
56              file.
57
58       -p phc-device
59              (This option is deprecated.)  Before Linux kernel v3.5 there was
60              no way to discover the PHC  device  associated  with  a  network
61              interface.    This   option   specifies  the  PHC  device  (e.g.
62              /dev/ptp0) to be used when running on legacy kernels.
63
64       -s     Enable the slaveOnly mode.
65
66       -l print-level
67              Set the maximum syslog level of messages which should be printed
68              or sent to the system logger. The default is 6 (LOG_INFO).
69
70       -m     Print messages to the standard output.
71
72       -q     Don't send messages to the system logger.
73
74       -v     Prints the software version and exits.
75
76       -h     Display a help message.
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78

LONG OPTIONS

80       Each and every configuration file option (see below) may also appear as
81       a "long" style command  line  argument.   For  example,  the  slaveOnly
82       option may be set using either of these two forms.
83
84              --slaveOnly 1   --slaveOnly=1
85
86       Option  values  given on the command line override values in the global
87       section of the configuration file.
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89

CONFIGURATION FILE

91       The configuration file is divided into sections.  Each  section  starts
92       with  a  line  containing  its name enclosed in brackets and it follows
93       with settings.  Each setting is placed on a separate line, it  contains
94       the  name  of  the option and the value separated by whitespace charac‐
95       ters. Empty lines and lines starting with # are ignored.
96
97       There are three different section types.
98
99
100       1.     The global section (indicated  as  [global])  sets  the  program
101              options,  clock options and default port options. Other sections
102              are port specific sections and they override  the  default  port
103              options.
104
105       2.     Port  sections  give  the  name  of  the  configured  port (e.g.
106              [eth0]).  Ports specified in the configuration file  don't  need
107              to  be  specified by the -i option. An empty port section can be
108              used to replace the command line option.
109
110       3.     Tables   for   configuring   unicast   discovery   begin    with
111              [unicast_master_table].
112
113              See UNICAST DISCOVERY OPTIONS, below.
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115

PORT OPTIONS

117       delayAsymmetry
118              The  time  difference in nanoseconds of the transmit and receive
119              paths. This value should be positive  when  the  master-to-slave
120              propagation time is longer and negative when the slave-to-master
121              time is longer. The default is 0 nanoseconds.
122
123       logAnnounceInterval
124              The mean time interval  between  Announce  messages.  A  shorter
125              interval  makes ptp4l react faster to the changes in the master-
126              slave hierarchy. The interval should be the same  in  the  whole
127              domain.  It's  specified  as  a  power  of  two in seconds.  The
128              default is 1 (2 seconds).
129
130       logSyncInterval
131              The mean time interval between Sync messages. A shorter interval
132              may  improve  accuracy  of  the local clock. It's specified as a
133              power of two in seconds.  The default is 0 (1 second).
134
135       logMinDelayReqInterval
136              The minimum permitted mean time interval between Delay_Req  mes‐
137              sages.  A  shorter  interval  makes  ptp4l  react  faster to the
138              changes in the path delay. It's specified as a power of  two  in
139              seconds.  The default is 0 (1 second).
140
141       logMinPdelayReqInterval
142              The minimum permitted mean time interval between Pdelay_Req mes‐
143              sages. It's specified as a power of two in seconds.  The default
144              is 0 (1 second).
145
146       announceReceiptTimeout
147              The  number of missed Announce messages before the last Announce
148              messages expires.  The default is 3.
149
150       syncReceiptTimeout
151              The number of sync/follow up messages that may go missing before
152              triggering a Best Master Clock election. This option is used for
153              running in gPTP mode according  to  the  802.1AS-2011  standard.
154              Setting  this option to zero will disable the sync message time‐
155              out.  The default is 0 or disabled.
156
157       transportSpecific
158              The transport specific field. Must be in the  range  0  to  255.
159              The default is 0.
160
161       ignore_transport_specific
162              By default, incoming messages are dropped if their transportSpe‐
163              cific field does not match the configured value.  However,  many
164              of  transports  specified  in the 1588 standard mandate ignoring
165              this field.  Moreover,  some  equipment  is  known  to  set  the
166              reserved  bits.   Configuring this option as 1 causes this field
167              to be ignored completely on receive.  The default is 0.
168
169       path_trace_enabled
170              Enable the mechanism used to trace the  route  of  the  Announce
171              messages.  The default is 0 (disabled).
172
173       follow_up_info
174              Include  the  802.1AS data in the Follow_Up messages if enabled.
175              The default is 0 (disabled).
176
177       fault_reset_interval
178              The time in seconds between the detection of a port's fault  and
179              the  fault  being  reset.  This value is expressed as a power of
180              two. Setting this value to -128  or  to  the  special  key  word
181              "ASAP"  will let the fault be reset immediately.  The default is
182              4 (16 seconds).
183
184       fault_badpeernet_interval
185              The time in seconds between the detection of a peer network mis‐
186              configuration  and  the  fault being reset. The port is disabled
187              for the duration of the interval. The value is  in  seconds  and
188              the  special  key  word ASAP will let the fault be reset immedi‐
189              ately.  The default is 16 seconds.
190
191       delay_mechanism
192              Select the delay mechanism. Possible values  are  E2E,  P2P  and
193              Auto.  The default is E2E.
194
195       hybrid_e2e
196              Enables  the  "hybrid" delay mechanism from the draft Enterprise
197              Profile. When enabled, ports in the slave state send their delay
198              request  messages to the unicast address taken from the master's
199              announce message. Ports in the master state will reply  to  uni‐
200              cast  delay  requests using unicast delay responses. This option
201              has no effect if the delay_mechanism is set to P2P.  The default
202              is 0 (disabled).
203
204       inhibit_multicast_service
205              Some  unicast mode profiles insist that no multicast message are
206              ever transmitted.  Setting this option inhibits multicast trans‐
207              mission.  The default is 0 (mutlicast enabled).
208
209       net_sync_monitor
210              Enables  the  NetSync  Monitor  (NSM) protocol. The NSM protocol
211              allows a station to measure how well another  node  is  synchro‐
212              nized.  The  monitor  sends a unicast delay request to the node,
213              which replies unconditionally with unicast delay response, sync,
214              and  follow  up  messages. If the monitor is synchronized to the
215              GM, it can use the time stamps in the message  to  estimate  the
216              node's  offset.   This  option  requires  that  the 'hybrid_e2e'
217              option be enabled as well.  The default is 0 (disabled).
218
219       unicast_listen
220              When enabled, this option allows the port to grant unicast  mes‐
221              sage  contracts.   Incoming requests for will be granted limited
222              only by the amount of memory available.  The default is 0  (dis‐
223              abled).
224
225       unicast_master_table
226              When  set to a positive integer, this option specifies the table
227              id to be used for unicast discovery.  Each table  lives  in  its
228              own section and has a unique, positive numerical ID.  Entries in
229              the table are a pair of transport  type  and  protocol  address.
230              Tables may not be shared between ports, but nothing prevents ta‐
231              ble entries from appearing in more than table.  The default is 0
232              (unicast discovery disabled).
233
234       unicast_req_duration
235              The  service time in seconds to be requested during unicast dis‐
236              covery.  Note that the remote node is free to grant a  different
237              duration.  The default is 3600 seconds or one hour.
238
239       ptp_dst_mac
240              The  MAC address to which PTP messages should be sent.  Relevant
241              only with L2 transport. The default is 01:1B:19:00:00:00.
242
243       p2p_dst_mac
244              The MAC address to which peer delay  messages  should  be  sent.
245              Relevant    only    with    L2   transport.   The   default   is
246              01:80:C2:00:00:0E.
247
248       network_transport
249              Select the network transport. Possible values are  UDPv4,  UDPv6
250              and L2.  The default is UDPv4.
251
252       neighborPropDelayThresh
253              Upper limit for peer delay in nanoseconds. If the estimated peer
254              delay is greater than this value  the  port  is  marked  as  not
255              802.1AS capable.
256
257       masterOnly
258              Setting  this  option to one (1) prevents the port from entering
259              the SLAVE state.  In  addition,  the  local  clock  will  ignore
260              Announce  messages received on this port. This option's intended
261              use is to  support  the  Telecom  Profiles  according  to  ITU-T
262              G.8265.1,  G.8275.1,  and G.8275.2. The default value is zero or
263              false.
264
265       G.8275.portDS.localPriority
266              The Telecom Profiles (ITU-T G.8275.1 and  G.8275.2)  specify  an
267              alternate  Best Master Clock Algorithm (BMCA) with a unique data
268              set comparison algorithm.  The value of this option  is  associ‐
269              ated with Announce messages arriving on a particular port and is
270              used as a tie breaker whenever clockClass,  clockAccuracy,  off‐
271              setScaledLogVariance,  and  priority2  are equal. This option is
272              only used when "dataset_comparison" is set  to  "telecom".   The
273              default value is 128.
274
275              Warning: the BMCA is guaranteed to produce a spanning tree (that
276              is, a timing network without loops) only when using the  default
277              values        of        G.8275.defaultDS.localPriority       and
278              G.8275.portDS.localPriority.   Careful  network  engineering  is
279              needed when using non-default values.
280
281       min_neighbor_prop_delay
282              Lower limit for peer delay in nanoseconds. If the estimated peer
283              delay is smaller than this value  the  port  is  marked  as  not
284              802.1AS capable.
285
286       tsproc_mode
287              Select  the  time stamp processing mode used to calculate offset
288              and delay.  Possible  values  are  filter,  raw,  filter_weight,
289              raw_weight.  Raw  modes  perform well when the rate of sync mes‐
290              sages (logSyncInterval) is similar to the rate of delay messages
291              (logMinDelayReqInterval  or  logMinPdelayReqInterval). Weighting
292              is useful with larger network jitters (e.g. software time stamp‐
293              ing).  The default is filter.
294
295       delay_filter
296              Select  the algorithm used to filter the measured delay and peer
297              delay. Possible values  are  moving_average  and  moving_median.
298              The default is moving_median.
299
300       delay_filter_length
301              The length of the delay filter in samples.  The default is 10.
302
303       egressLatency
304              Specifies  the  difference  in  nanoseconds  between  the actual
305              transmission time at the reference plane and the reported trans‐
306              mit  time  stamp. This value will be added to egress time stamps
307              obtained from the hardware.  The default is 0.
308
309       ingressLatency
310              Specifies the difference in  nanoseconds  between  the  reported
311              receive  time  stamp  and the actual reception time at reference
312              plane. This value will be subtracted from  ingress  time  stamps
313              obtained from the hardware.  The default is 0.
314
315       boundary_clock_jbod
316              When  running  as  a boundary clock (that is, when more than one
317              network interface is configured), ptp4l performs a sanity  check
318              to make sure that all of the ports share the same hardware clock
319              device. This option allows ptp4l to work  as  a  boundary  clock
320              using  "just  a  bunch  of devices" that are not synchronized to
321              each other. For this mode, the collection of clocks must be syn‐
322              chronized  by  an  external  program,  for example phc2sys(8) in
323              "automatic" mode.  The default is 0 (disabled).
324
325       udp_ttl
326              Specifies the Time to live (TTL) value for IPv4  multicast  mes‐
327              sages and the hop limit for IPv6 multicast messages. This option
328              is only relevant with the IPv4  and  IPv6  UDP  transports.  The
329              default  is 1 to restrict the messages sent by ptp4l to the same
330              subnet.
331
332

PROGRAM AND CLOCK OPTIONS

334       twoStepFlag
335              Enable two-step mode for sync messages.  One-step  mode  can  be
336              used  only  with  hardware  time  stamping.   The  default  is 1
337              (enabled).
338
339       slaveOnly
340              The local clock is a slave-only clock if enabled.   This  option
341              is  only  for use with 1588 clocks and should not be enabled for
342              802.1AS clocks.  The default is 0 (disabled).
343
344       gmCapable
345              If this option is enabled, then  the  local  clock  is  able  to
346              become  grand  master.  This is only for use with 802.1AS clocks
347              and has no effect on 1588 clocks.  The default is 1 (enabled).
348
349       priority1
350              The priority1 attribute of the local clock. It is  used  in  the
351              best  master  selection algorithm, lower values take precedence.
352              Must be in the range 0 to 255.  The default is 128.
353
354       priority2
355              The priority2 attribute of the local clock. It is  used  in  the
356              best  master  selection algorithm, lower values take precedence.
357              Must be in the range 0 to 255.  The default is 128.
358
359       clockClass
360              The clockClass attribute of the  local  clock.  It  denotes  the
361              traceability  of  the time distributed by the grandmaster clock.
362              The default is 248.
363
364       clockAccuracy
365              The clockAccuracy attribute of the local clock. It  is  used  in
366              the best master selection algorithm.  The default is 0xFE.
367
368       offsetScaledLogVariance
369              The  offsetScaledLogVariance  attribute  of  the local clock. It
370              characterizes the  stability  of  the  clock.   The  default  is
371              0xFFFF.
372
373       G.8275.defaultDS.localPriority
374              The  Telecom  Profiles  (ITU-T G.8275.1 and G.8275.2) specify an
375              alternate Best Master Clock Algorithm (BMCA) with a unique  data
376              set  comparison  algorithm.  The value of this option is associ‐
377              ated with the local clock and is used as a tie breaker  whenever
378              clockClass,  clockAccuracy,  offsetScaledLogVariance, and prior‐
379              ity2 are equal. This option is only used when  "dataset_compari‐
380              son" is set to "telecom".  The default value is 128.
381
382              Warning: the BMCA is guaranteed to produce a spanning tree (that
383              is, a timing network without loops) only when using the  default
384              values        of        G.8275.defaultDS.localPriority       and
385              G.8275.portDS.localPriority.   Careful  network  engineering  is
386              needed when using non-default values.
387
388       domainNumber
389              The domain attribute of the local clock.  The default is 0.
390
391       utc_offset
392              The current offset between TAI and UTC.  The default is 37.
393
394       free_running
395              Don't adjust the local clock if enabled.  The default is 0 (dis‐
396              abled).
397
398       freq_est_interval
399              The time interval over which is estimated the ratio of the local
400              and peer clock frequencies. It is specified as a power of two in
401              seconds.  The default is 1 (2 seconds).
402
403       assume_two_step
404              Treat one-step responses as two-step if enabled. It is  used  to
405              work  around  buggy  802.1AS  switches.   The default is 0 (dis‐
406              abled).
407
408       tc_spanning_tree
409              When running as a Transparent  Clock,  increment  the  "stepsRe‐
410              moved"  field of Announce messages that pass through the switch.
411              Enabling this option ensures that PTP message loops never  form,
412              provided  the  switches  all implement this option together with
413              the BMCA.
414
415       tx_timestamp_timeout
416              The number of milliseconds to poll waiting for the tx time stamp
417              from  the  kernel  when  a  message has recently been sent.  The
418              default is 1.
419
420       check_fup_sync
421              Because of packet reordering that can occur in the  network,  in
422              the  hardware,  or  in the networking stack, a follow up message
423              can appear to arrive in the application before the matching sync
424              message. As this is a normal occurrence, and the sequenceID mes‐
425              sage field ensures proper matching, the  ptp4l  program  accepts
426              out of order packets. This option adds an additional check using
427              the software time stamps from the  networking  stack  to  verify
428              that the sync message did arrive first. This option is only use‐
429              ful if you do not trust the sequence IDs generated by  the  mas‐
430              ter.  The default is 0 (disabled).
431
432       clock_servo
433              The  servo  which  is used to synchronize the local clock. Valid
434              values are "pi" for a PI controller, "linreg"  for  an  adaptive
435              controller  using  linear  regression,  "ntpshm" for the NTP SHM
436              reference clock to allow  another  process  to  synchronize  the
437              local  clock  (the  SHM segment number is set to the domain num‐
438              ber), and "nullf" for a servo that always dials frequency offset
439              zero (for use in SyncE nodes).  The default is "pi."
440
441       clock_type
442              Specifies  the  kind  of  PTP  clock.  Valid values are "OC" for
443              ordinary clock, "BC" for boundary clock, "P2P_TC"  for  peer  to
444              peer  transparent clock, and "E2E_TC" for end to end transparent
445              clock.  An multi-port ordinary clock will automatically be  con‐
446              figured as a boundary clock.  The default is "OC".
447
448       pi_proportional_const
449              The proportional constant of the PI controller. When set to 0.0,
450              the proportional constant will be set by the  following  formula
451              from the current sync interval.  The default is 0.0.
452
453              kp = min(kp_scale * sync^kp_exponent, kp_norm_max / sync)
454
455       pi_integral_const
456              The integral constant of the PI controller. When set to 0.0, the
457              integral constant will be set by the following formula from  the
458              current sync interval.  The default is 0.0.
459
460              ki = min(ki_scale * sync^ki_exponent, ki_norm_max / sync)
461
462       pi_proportional_scale
463              The  kp_scale  constant  in  the formula used to set the propor‐
464              tional constant of the PI controller  from  the  sync  interval.
465              When set to 0.0, the value will be selected from 0.7 and 0.1 for
466              the hardware  and  software  time  stamping  respectively.   The
467              default is 0.0.
468
469       pi_proportional_exponent
470              The  kp_exponent constant in the formula used to set the propor‐
471              tional constant of the PI controller  from  the  sync  interval.
472              The default is -0.3.
473
474       pi_proportional_norm_max
475              The  kp_norm_max constant in the formula used to set the propor‐
476              tional constant of the PI controller  from  the  sync  interval.
477              The default is 0.7
478
479       pi_integral_scale
480              The  ki_scale  constant  in the formula used to set the integral
481              constant of the PI controller from the sync interval.  When  set
482              to  0.0,  the  value will be selected from 0.3 and 0.001 for the
483              hardware and software time stamping respectively.   The  default
484              is 0.0.
485
486       pi_integral_exponent
487              The ki_exponent constant in the formula used to set the integral
488              constant of the PI  controller  from  the  sync  interval.   The
489              default is 0.4.
490
491       pi_integral_norm_max
492              The ki_norm_max constant in the formula used to set the integral
493              constant of the PI  controller  from  the  sync  interval.   The
494              default is 0.3.
495
496       step_threshold
497              The  maximum offset the servo will correct by changing the clock
498              frequency instead of stepping the clock. When set  to  0.0,  the
499              servo  will never step the clock except on start. It's specified
500              in seconds.  The default is 0.0.  This option used to be  called
501              pi_offset_const.
502
503       first_step_threshold
504              The  maximum offset the servo will correct by changing the clock
505              frequency instead of stepping the clock. This is only applied on
506              the  first  update.  It's specified in seconds. When set to 0.0,
507              the servo won't step the clock on start.  The default is 0.00002
508              (20  microseconds).   This  option  used  to be called pi_f_off‐
509              set_const.
510
511       max_frequency
512              The maximum allowed frequency adjustment of the clock  in  parts
513              per  billion  (ppb).  This is an additional limit to the maximum
514              allowed by the hardware. When set to 0, the hardware limit  will
515              be  used.   The default is 900000000 (90%).  This option used to
516              be called pi_max_frequency.
517
518       sanity_freq_limit
519              The maximum allowed frequency offset between  uncorrected  clock
520              and  the system monotonic clock in parts per billion (ppb). This
521              is used as a sanity check of  the  synchronized  clock.  When  a
522              larger offset is measured, a warning message will be printed and
523              the servo will be reset. When set to 0, the sanity check is dis‐
524              abled. The default is 200000000 (20%).
525
526       initial_delay
527              The initial path delay of the clock in nanoseconds used for syn‐
528              chronization of the clock before the delay is measured using the
529              E2E  or  P2P delay mechanism. If set to 0, the clock will not be
530              updated until the delay is measured.  The default is 0.
531
532       ntpshm_segment
533              The number of the SHM segment used by ntpshm servo.  The default
534              is 0.
535
536       udp6_scope
537              Specifies  the  desired  scope  for the IPv6 multicast messages.
538              This will be used as the second byte  of  the  primary  address.
539              This option is only relevant with IPv6 transport.  See RFC 4291.
540              The default is 0x0E for the global scope.
541
542       uds_address
543              Specifies the address of the UNIX domain  socket  for  receiving
544              local management messages. The default is /var/run/ptp4l.
545
546       dscp_event
547              Defines  the Differentiated Services Codepoint (DSCP) to be used
548              for PTP event messages. Must be a value between 0 and 63.  There
549              are  several  media  streaming  standards out there that require
550              specific values for this option.  For example  46  (EF  PHB)  in
551              AES67 or 48 (CS6 PHB) in RAVENNA. The default is 0.
552
553       dscp_general
554              Defines  the Differentiated Services Codepoint (DSCP) to be used
555              for PTP general messages. Must be a  value  between  0  and  63.
556              There  are several media streaming standards out there that rec‐
557              ommend specific values for this option.  For  example  34  (AF41
558              PHB) in AES67 or 46 (EF PHB) in RAVENNA. The default is 0.
559
560       dataset_comparison
561              Specifies  the method to be used when comparing data sets during
562              the Best  Master  Clock  Algorithm.   The  possible  values  are
563              "ieee1588" and "G.8275.x".  The default is "ieee1588".
564
565       logging_level
566              The  maximum  logging level of messages which should be printed.
567              The default is 6 (LOG_INFO).
568
569       message_tag
570              The tag which is added to all messages printed to  the  standard
571              output  or  system  log.   The default is an empty string (which
572              cannot be set in the configuration file as the  option  requires
573              an argument).
574
575       verbose
576              Print  messages  to the standard output if enabled.  The default
577              is 0 (disabled).
578
579       use_syslog
580              Print messages to the system log if enabled.  The default  is  1
581              (enabled).
582
583       summary_interval
584              The time interval in which are printed summary statistics of the
585              clock. It is specified as a power of two in seconds. The statis‐
586              tics  include  offset  root  mean square (RMS), maximum absolute
587              offset, frequency offset mean and standard deviation,  and  path
588              delay mean and standard deviation. The units are nanoseconds and
589              parts per billion (ppb). If there is only one  clock  update  in
590              the  interval, the sample will be printed instead of the statis‐
591              tics. The messages are  printed  at  the  LOG_INFO  level.   The
592              default is 0 (1 second).
593
594       time_stamping
595              The time stamping method. The allowed values are hardware, soft‐
596              ware and legacy.  The default is hardware.
597
598       productDescription
599              The product description string. Allowed values must  be  of  the
600              form manufacturerName;modelNumber;instanceIdentifier and contain
601              at most 64 utf8 symbols. The default is ";;".
602
603       revisionData
604              The revision description string which contains the revisions for
605              node  hardware  (HW),  firmware (FW), and software (SW). Allowed
606              values are of the form HW;FW;SW and contain at most 32 utf8 sym‐
607              bols. The default is an ";;".
608
609       userDescription
610              The  user  description  string.  Allowed  values are of the form
611              name;location and contain at most 128 utf8 symbols. The  default
612              is an empty string.
613
614       manufacturerIdentity
615              The manufacturer id which should be an OUI owned by the manufac‐
616              turer.  The default is 00:00:00.
617
618       kernel_leap
619              When a leap second is announced, let  the  kernel  apply  it  by
620              stepping  the  clock instead of correcting the one-second offset
621              with servo, which would correct the one-second offset slowly  by
622              changing  the  clock frequency (unless the step_threshold option
623              is set to correct such offset by stepping).  Relevant only  with
624              software time stamping. The default is 1 (enabled).
625
626       timeSource
627              The  time source is a single byte code that gives an idea of the
628              kind of local clock in use. The value is  purely  informational,
629              having  no  effect on the outcome of the Best Master Clock algo‐
630              rithm, and is advertised when the clock becomes grand master.
631
632

UNICAST DISCOVERY OPTIONS

634       table_id
635              Each table must begin with a unique,  positive  table  ID.   The
636              port  that  claims  a given table does so by including the ID as
637              the value of its 'unicast_master_table' option.
638
639       logQueryInterval
640              This option configures the time to wait between unicast negotia‐
641              tion  attempts.   It  is specified as a power of two in seconds.
642              The default is 0 (1 second).
643
644       peer_address
645              This option specifies the unicast address of the  peer  for  use
646              with  the  peer to peer delay mechanism.  If specified, the port
647              owning the table will negotiate  unicast  peer  delay  responses
648              from the machine at the given remote address, otherwise the port
649              will send multicast peer delay requests.
650
651       L2|UDPv4
652              Each table  entry  specifies  the  transport  type  and  network
653              address  of  a potential remote master.  If multiple masters are
654              specified, then unicast negotiation will be performed with  each
655              if them.
656
657

TIME SCALE USAGE

659       ptp4l  as  domain master either uses PTP or UTC time scale depending on
660       time stamping mode.  In software and  legacy  time  stamping  modes  it
661       announces  Arbitrary time scale mode, which is effectively UTC here, in
662       hardware time stamping mode it announces use of PTP time scale.
663
664       When ptp4l is the domain master using hardware time stamping, it is  up
665       to  phc2sys  to  maintain the correct offset between UTC and PTP times.
666       See phc2sys(8) manual page for more details.
667
668

SEE ALSO

670       pmc(8), phc2sys(8)
671
672
673
674linuxptp                          April 2018                          PTP4l(8)
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