ITU-T PTP Telecom Profile for Phase/Time, (G.8275.2 Annex A)
Owned by Gordon Muir (Deactivated)
Latest document version: | ITU-T Recommendation G.8275.2, 11/2022 (full text publication) | |
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Location: | http://www.itu.int/rec/T-REC-G.8275.2/en | |
Objective: | Time distribution to better than ±1.5µs over a partial timing support network |
Feature/ Parameter | Note | Range | Default Value | G.8275.2 Clause | ||
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from | to | |||||
Profile Identification | ||||||
profileName: | ITU-T PTP profile for phase/time distribution with partial timing support from the network (unicast mode) | Annex A.1 | ||||
profileVersion: | 2.2 (IEEE1588-2008) / 2.3 (IEEE1588-2019) | Annex A.1 | ||||
profileIdentifier: | 00-19-A7-02-02-02 / 00-19-A7-02-02-03 | Annex A.1 | ||||
Specified by: | ITU-T | Annex A.1 | ||||
Location: | www.itu.int | Annex A.1 | ||||
PTP Options | ||||||
Permitted Nodes | Ordinary clocks (i.e. Grandmasters, slave-only clocks), boundary clocks | Annex A.3.1, 6.2.3 | ||||
Prohibited Nodes | None. Transparent Clocks are for further study. | Annex A.3.1 | ||||
Transport Mechanisms | Both masters and slaves must support IEEE1588-2008 Annex D IPv4/UDP stack. Bit 0 of the transportSpecific field must be set to "0". Both masters and slaves may support IEEE1588-2008 Annex E IPv6/UDP stack | Annex A.3.2, 6.4 | ||||
Multicast or Unicast | Both masters and slaves must support full unicast operation (see details below) | Annex A.3.3, 6.3.3 | ||||
BMCA | Alternate BMCA specified (see details below) | Annex A.4, 6.7 | ||||
Path Delay Measurement | Uses delay_request/response mechanism, if required (i.e. for two-way operation) Peer delay mechanism must not be used. | Annex A.5 | ||||
PTP Management | Not specified in this version of the profile. | Annex A.6 | ||||
Clock Identity | EUI-64 (as specified in clause 7.5.2.2.2 of IEEE1588-2008) | Annex A.7 | ||||
Message Types | Used: Announce, Sync, Follow-up, Delay_Req, Delay_Resp, Signaling Not used: Pdelay_Req, Pdelay_Resp, Pdelay_Resp_Follow_Up The use of Management messages is for further study. | 6.2.2 | ||||
One-step and Two-step clock | Clocks may transmit messages using either one-step or two-step modes. Clocks must be capable of receiving and handling messages from both one-step and two-step clocks, without configuration. | 6.3.2 | ||||
One-way and Two-way Operation | Masters must support both one-way and two-way operation. Slaves may support either one-way or two-way, or both. | 6.3.1 | ||||
Security | For further study. IEEE1588-2008 Annex K experimental security protocol is not used | Annex A.8, 8 | ||||
Unicast negotiation (IEEE1588-2008 clause 16.1) | Mandatory - see details below | Annex A.3.4, A.3.5, 6.6 | ||||
Path trace (IEEE1588-2008 clause 16.2) | Not mentioned. | - | ||||
Alternate timescales (IEEE1588-2008 clause 16.3) | PTP timescale used. Alternate timescales are not used in this profile. | Annex A.9 | ||||
Grandmaster clusters (IEEE1588-2008 clause 17.3) | Not used in this profile | Annex A.9 | ||||
Alternate masters (IEEE1588-2008 clause 17.4) | Not used in this profile | Annex A.9 | ||||
Unicast discovery (IEEE1588-2008 clause 17.5) | Not mentioned. | - | ||||
Acceptable master table (IEEE1588-2008 clause 17.6) | Not used in this profile | Annex A.9 | ||||
Cumulative frequency scale factor offset (IEEE1588-2008 Annex L) | Not used in this profile | Annex A.9 | ||||
Message Rates | ||||||
Sync & Follow-up | 1 per second to 128 per second | 1 | 128 | - | 6.5 | |
Delay_request/response | 1 per second to 128 per second | 1 | 128 | - | ||
Announce | 1 per second to 8 per second | 1 | 8 | - | ||
Peer Delay_request/response | None (uses Delay_request/response mechanism) | |||||
Signaling | As required for unicast negotiation | |||||
Management | Not used | |||||
PTP Configurable Attribute Values(all others as per PTP, defined in IEEE1588-2008) | ||||||
Default data set (configurable members) | ||||||
twoStepFlag | Used as per PTP, according to clock's capability | FALSE | TRUE | Table A.1 | ||
clockIdentity | Based on EUI64 format, as per PTP | Table A.1, Annex A.7 | ||||
numberPorts | Always 1 for ordinary clocks (Grandmasters, slaves) | Ordinary clocks | 1 | 1 | Table A.1 | |
As required for Boundary or Transparent clocks | BC, TC | 1 | N | |||
clockQuality.clockClass | Grandmaster clocks | 6, 7, 140, 150, 160, 248 | 248 | Table A.1, 6.7.5, Table 2 | ||
Boundary clocks | 135, 165, 248 | 248 | ||||
Slave-only clocks | 255 | 255 | ||||
clockQuality.clockAccuracy | Grandmaster clocks locked to an ePRTC | 0x20 | 0xFE | Table A.1, 6.7.6 | ||
Grandmaster clocks locked to a PRTC | 0x21 | |||||
Grandmaster clocks not locked to a PRTC | 0xFE | |||||
Boundary clocks and slave-only clocks | 0xFE | |||||
clockQuality. offsetScaledLogVariance | Grandmaster clocks locked to an ePRTC | 0x4B32 | 0xFFFF | Table A.1, 6.7.7 | ||
Grandmaster clocks locked to a PRTC | 0x4E5D | |||||
Grandmaster clocks not locked to a PRTC | 0xFFFF | |||||
Boundary clocks and slave-only clocks | 0xFFFF | |||||
priority1 | Not used. For all clock types, must be set to default value. | 128 | 128 | Table A.1, 6.7.3 | ||
priority2 | Used to set network and protection topology, as described in Appendix I | Grandmasters, boundary clocks | 0 | 255 | 128 | Table A.1, 6.7.4 |
Slave-only clocks | 255 | 255 | ||||
domainNumber | All clock types | 44 | 63 | 44 | Table A.1 6.2.1 | |
slaveOnly | Grandmasters and boundary clocks | FALSE | FALSE | Table A.1 | ||
Slave-only clocks | TRUE | TRUE | ||||
Profile-specific defaultDS attributes | ||||||
localPriority | New dataset member defined in profile, allowing operators to manually configure topology (Annex B) | 1 | 255 | 128 | Table A.1, 6.7.2 | |
Port data set (configurable members) | ||||||
portIdentity.clockIdentity | Based on EUI64 format, as per PTP | Table A.5 | ||||
portIdentity.portNumber | Always 1 for ordinary clocks Boundary clocks as required for device | Ordinary clocks | 1 | 1 | Table A.5 | |
Boundary clocks | 1 | N | ||||
logMinDelayReqInterval | Delay_Req message rate: covered by unicast negotiation (see details below) | Table A.5 | ||||
logAnnounceInterval | Announce message rate: covered by unicast negotiation (see details below) | Table A.5 | ||||
announceReceiptTimeout | Timeout period before declaring loss of announce service | 2 missing messages | 2 | 2 | Table A.5 | |
logSyncInterval | Sync message rate: covered by unicast negotiation (see details below) | Table A.5 | ||||
delayMechanism | Two-way capable slave (E2E mechanism) | 0x01 | 0x01 | Table A.5 | ||
One-way capable slave (Disabled) | 0xFE | 0xFE | Table A.5 | |||
logMinPdelayReqInterval | Pdelay message rate: not used in this profile | Table A.5 | ||||
versionNumber | PTP protocol version number: Version 2 only | 2 | 2 | Table A.5 | ||
Profile-specific portDS attributes | ||||||
masterOnly | New dataset member defined in profile, allowing multiple simultaneous active GMs. TRUE for ports that are always in master state. | Grandmaster clocks | TRUE | TRUE | Table A.5, 6.7.1 | |
Boundary clocks | FALSE | TRUE | TRUE | |||
Slave clocks | FALSE | FALSE | ||||
localPriority | New dataset member defined in profile, allowing operators to manually configure topology (Annex B) | 1 | 255 | 128 | Table A.5, 6.7.1 | |
SF | New dataset member defined in profile TRUE when a slave port is in signal failure | TRUE | FALSE | Table A.5 | ||
PTP common message header flags | ||||||
alternateMasterFlag | In Announce messages: set FALSE on transmission when port state is MASTER. Announce messages discarded on reception if flag is TRUE. | FALSE | TRUE | 6.9, Table A.6 | ||
twoStepFlag | Used as per PTP defined in IEEE1588-2008 | FALSE | TRUE | Table A.6 | ||
unicastFlag | Set TRUE on transmission. | TRUE | TRUE | Table A.6 | ||
PTP profile Specific1 | Set FALSE on transmission; ignored on reception. | FALSE | FALSE | Table A.6 | ||
PTP profile Specific2 | Set FALSE on transmission; ignored on reception. | FALSE | FALSE | Table A.6 | ||
Reserved | Set FALSE on transmission; ignored on reception. | FALSE | FALSE | Table A.6 | ||
leap61 | Used as per PTP defined in IEEE1588-2008 | FALSE | TRUE | Table A.6 | ||
leap59 | Used as per PTP defined in IEEE1588-2008 | FALSE | TRUE | Table A.6 | ||
currentUTCOffsetValid | Used as per PTP defined in IEEE1588-2008 | FALSE | TRUE | Table A.6 | ||
ptpTimescale | Set TRUE on transmission. | TRUE | TRUE | Table A.6 | ||
timeTraceable | Used as in Table 2 | FALSE | TRUE | Table A.6, Table 2 | ||
frequencyTraceable | Used as in Table 2 | FALSE | TRUE | Table A.6, Table 2 | ||
controlField | Not used; ignored on reception. | 6.7.10 | ||||
Profile-specific common message header flags | ||||||
synchronizationUncertain | Profile specific optional flag in octet 1, bit 6, indicating that the source of synchronization is uncertain (e.g. clock is in UNCALIBRATED state while switching to a new T-GM). | FALSE | TRUE | FALSE | Table A.6, Annex E | |
Unicast and Multicast Operation | ||||||
Full multicast operation | Not used in this profile. | Annex A.3.3 | ||||
Full unicast operation | Both master ports and slave ports must support full unicast operation | 6.3.3, Annex A.3.3 | ||||
Hybrid unicast/multicast | Not used in this profile. | Annex A.3.3 | ||||
Unicast negotiation process | Both masters and slaves must support unicast negotiation (IEEE1588-2008 Clause 16.1). Unicast connection establishment without negotiation is for further study. | Annex A.3.3, 6.6 | ||||
targetPortIdentity | Requesting port may use all 1's as the initial value. On receiving a response, it may use all 1's, or use the clockIdentity/portNumber of grant port Grant port may use all 1's, or use the clockIdentity/portNumber of requesting port | 6.6 | ||||
duration field | Duration of unicast service lease | 60 | 1000 | 300 | Annex A.3.4, 6.6 | |
logInterMessagePeriod | Masters must be capable of accepting the entire ranges specified. Slaves must operate within these ranges, but do not have to use the entire ranges. | Annex A.3.4, 6.5 | ||||
Sync & Follow-up (from 128 to 1 messages per second) | -7 | 0 | - | |||
Delay_request/response (from 128 to 1 messages per second) | -7 | 0 | - | |||
Announce (from 8 to 1 messages per second) | -3 | 0 | - | |||
R (Renewal Invited) | Set FALSE on transmission; ignored on reception. | FALSE | FALSE | 6.6 | ||
logQueryInterval | Slaves must wait a minimum of 1 second before repeating a unicast negotiation request. Note: If three consecutive requests are denied or not answered, slaves must wait 60s before repeating the request to the same master. | 1 | 6.6 | |||
number of TLVs | Master must accept multiple unicast request TLVs in the same signaling message Slaves may include multiple unicast request TLVs in the same signaling message Master may include multiple unicast grant TLVs in the same signaling message Slaves must accept multiple unicast grant TLVs in the same signaling message | 1 | 3 | 6.6 | ||
Best Master Clock Algorithm (BMCA) | ||||||
BMCA type: | Alternate BMCA (modified default BMCA) | 6.7 | ||||
State decision algorithm | Based on default state decision algorithm, adding check for new parameter masterOnly | 6.7.8 | ||||
Data set comparison algorithm | Based on default data set comparison with following changes: - moves check on GM clockIdentity to end - removes check on GM priority1 values - adds check for new parameter localPriority value (after GM priority2) | 6.7.9 | ||||
Additional flags/fields | ||||||
PTSF-lossSync | If the slave no longer receives the timing messages sent by a master (i.e., Sync and subsequently Follow_up and Delay_Resp messages), then a PTSF‑lossSync associated to this master must occur. | FALSE | TRUE | FALSE | 6.7.11 | |
PTSF-unusable | If the PTP packet timing signal is not usable for the slave to achieve the performance target, then a PTSF-unusable associated to this master must occur. | FALSE | TRUE | FALSE | 6.7.11 | |
Profile-specific TLVs | ||||||
PTP Interface Rate | Optional TLV communicating the bit rate of the master port. Used to determine rate asymmetry on the path between master and slave port, allowing the slave port to compensate for the resulting delay asymmetry. Attached to the signalling message containing the GRANT_UNICAST_TRANSMISSION TLV. | Annex D |
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