Why is the IEEE 1588 PTP delay/offset measurement is inconsistent on Triple Speed Ethernet Intel® FPGA IP ? Description. Due to a problem with the Intel® Quartus® Prime software version 21.2 and earlier, the result of Triple Speed Ethernet Intel® FPGA IP internal latency measurement could potentially drift when Tx cloc The way the PTP equations were set up, the offset is subtracted from the current time, so the slave will have to decrease its clock by -1:55, or advance it by 1:55. With the asymmetric delay, PTP gave averaged out the message latencies, resulting in an offset of -1:55 instead of the correct value of -2:00 The basic principle of PTP is as follows: Slave time = master time + propagation delay + offset. The purpose of the protocol is to align the slave and the master time so that the gap between them is the propagation delay of the packet PTP is capable of synchronizing multiple clocks to better than 100 nanoseconds on a network specifically designed for IEEE-1588. A Network Time Server with PTP is typically referred to as an IEEE-1588 Grandmaster or PTP Grandmaster. One way delay or Offset = ((T2 - T1) - (T4 - T3)) / ptp4l [1434165.342]: selected / dev / ptp4 as PTP phc2sys [1434344.651]: CLOCK_REALTIME phc offset 450 s2 freq-39119 delay 1354 phc2sys [1434344.776]: CLOCK_REALTIME phc offset 499 s2 freq-38620 delay 1344 phc2sys [1434344.902]: CLOCK_REALTIME phc offset 485 s2 freq-38484 delay 1347 phc2sys [1434345.027]: CLOCK_REALTIME phc offset 476 s2 freq-38348 delay 1346 phc2sys [1434345.153]: CLOCK.
PTP monitoring records PTP information including offset from master, mean path delay, and skew values, which can then be viewed using a show comm and. When this feature is enabled, PTP Syslog messages will also be generated for those metrics for which threshold values have been configured on the switch. PTP monitoring is enabled by default Oh no! Some styles failed to load. Please try reloading this pag
The short answer is that the peer-to-peer delay measurement mechanism is best in an engineered network, where all switches (and routers if there are any) can be guaranteed to be 1588 capable, i.e. they are either transparent clocks or boundary clocks The Precision Time Protocol, PTP, defined by IEEE 1588-2008 works by exchanging messages between master clocks and slave clocks. Figure 1. Sequence diagram showing the exchange of messages between a PTP master clock and a PTP slave clock. The departure and arrival times of the Sync and Delay_Request messages are saved as the four timestamps t1-t4 There are two mechanisms used in PTP to measure the propagation delay between PTP ports: The Delay Request-Response Mechanism This mechanism uses the messages Sync, Delay_Req, Delay_Resp and, if required, Follow_Up. the propagation delay will be measured less than the clock offset correction. (1). PTP IEEE 1588 stack for Linux Brought to you by: rcochran. Summary Files Reviews Support Code Mailing Lists Menu. 5 One-Way Delay and PTP (IEEE 1588v2) Test Applications Use Case: Perform 1 PPS Wander Analysis In this use case, the provider must verify that the 1PPS service provided by the PTP slave is accurately traceable to external reference equipment
PTP messages and measure packet delay variation (PDV) stability over time which is a key parameter to maintain the quality. Case Study I: Set up a PTP Synchronization Network The PTP protocol requires the establishment of time synchronization be-tween master and slave nodes during the handshaking. This process occur 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 Synchronization in PTP PTP uses sync messages and delay request messages to measure round- trip delay And delay response message to get t. 4. timestamp back to slave Master to slave delay is calculated as: Delay = [(t. 4 - t. 1) - (t. 3 - t. 2)] / 2 Subtracts time slave took to respond to sync message from roundtrip delay seem by maste
The offset delay between PTP Master Device and PTP Slave Device should be near to 9 nanoseconds as per the theoretical achievable granularity for this configuration. The current implementation is able to achieve the +/-500 ns granularity and will be optimized for the better granularity While it is possible to use master-slave mode in PTP, this requires an awkward message exchange and is not likely to be used in practice. 3.2. Broadcast Mode. In broadcast mode for both NTP and PTP, the offset expression has an inverted sign, while the delay calculation is the same
PTP monitoring records PTP information including offset from master, mean path delay, and skew values, which can then be viewed using a show command. When this feature is enabled, PTP Syslog messages will also be generated for those metrics for which threshold values have been configured on the switch. PTP monitoring is enabled by default PTP header Bits Length [octets] Offset [octets] 7 6 5 4 3 2 1 0 transportSpecific = 0000: messageType Sync = 0 Delay_Req = 1 Follow_Up = 8 Delay_Resp = 9: 1: 0 reserved: versionPTP = 2: 1: 1 messageLength including header, body, suffix: 2: 2 domainNumber same on communicating device # ptp4l -m -i eth0 selected eth0 as PTP clock port 1: INITIALIZING to LISTENING on INITIALIZE port 0: INITIALIZING to LISTENING on INITIALIZE port 1: new foreign master 00a152.fffe.0b334d-1 selected best master clock 00a152.fffe.0b334d port 1: LISTENING to UNCALIBRATED on RS_SLAVE master offset -25937 s0 freq +0 path delay 12340 master offset -27887 s0 freq +0 path delay 14232 master offset. Still, the delay attack on PTP messages is one of the frailties of these solutions. The reason is that due to the property of PTP messages (size, direction, and period of transmission), an attacker can launch a delay attack even on encrypted messages. This paper presents a solution to detect delay attacks
ptp4l[537898.093]: master offset 641 s2 freq -8446 path delay 513 ptp4l[537899.093]: master offset 570 s2 freq -8324 path delay 533 ptp4l[537900.093]: master offset 389 s2 freq -8334 path delay 533 Offset between Master and Slave(PHC PTP typically uses the same epoch as Unix time (start of 1 January 1970). While the Unix time is based on Coordinated Universal Time (UTC) and is subject to leap seconds, PTP is based on International Atomic Time (TAI). The PTP grandmaster communicates the current offset between UTC and TAI, so that UTC can be computed from the received PTP time Thus; PTP clock messages can get stuck and delayed in the backbone; in the switches between your devices. As previously mentioned, v2 is not backwards compatible with v1. When the AES67 interoperability standard was published, it mandated the use of PTPv2 Dear All, I am using PTP Time Sync via Solarflare network card. It is difficult to use because of the high PTP Offset. If you change it to Onboard NIC and use it, the Offset falls within the normal range. When using linuxptp, the offset corresponds to the normal range. Use X2522-25G (Solarflare Xt..
PTP Delay Mechanism# The delay measurement mechanism defines how PTP delay measurement messages are sent and received within the network. GevIEEE1588OffsetFromMaster: Indicates the estimated temporal offset between the master clock and the clock of the current PTP device in ticks (1 tick = 1 nanosecond) 3 PTP Accuracy Now the Slave clock can calculate both the clock offset and the transmission delay using both timestamp differences. 3 PTP Accuracy ; The overall accuracy depends on several factors, the most obvious one being the precision with which the timestamps can be taken Defined in IEEE Std 1588™-2008 (1588v2), Precision Time Protocol (PTP) is a protocol that distributes frequency, phase and time over packet based networks 1. It is also important to note how the equation for offset uses the mean_path_delay. If the delays in the two directions are actually different,. ptp4l[59.974]: path delay 215360 229562 ptp4l[60.188]: master offset 625645199 s0 freq +18054 path delay 215360 ptp4l[61.188]: master offset 625657327 s0 freq +18054 path delay 215360 ptp4l[61.965]: port 1: delay timeout ptp4l[61.966]: path delay n 221227 e c 22122 SCAA055 Defining Skew, Propagation-Delay, Phase Offset (Phase Error) 7 In general, not all-skew parameters are of interest, but their discussion is included for illustration. The goal is to minimize skew to an acceptable value. The rule of thumb is that clock ske
delay : 网络延时（报文在网络中传输带来的延时） 从时钟可以通过 t1,t2,t3,t4 四个精确时间戳信息，得到主从时钟偏差 offset 和传输延时 delay: 从时钟得到 offset 和 delay 之后就可以通过修正本地时钟进行时间同步。 PTP报文分 1.2 Definition and Derivation of Two-Way Delay and Offset The most fundamental purpose of PTP is to synchronize the time between clocks, so the foundation of PTP is the Delay Calculation. To synchronize between two clocks, the master clock sends timestamps to the slave clock using one of two methods, One-Way Delay or Two-Way Delay PTP P2P Transparent Clock Switch/Router Switch function Residence Time Bridge Peer to Peer Transparent Clocks •Peer to peer messages measure the round trip link delay •Link delay and residence time added to the correction field •At the slave, the value of the correction field represents the total delay from master to slav There are two elements to synchronize: offset and delay. Offset . First the slaves corrects the offset depending on a messages received from the master. This message called Sync contains the current time of the master. To include the exact time of transmission (moment when the first byte of the message is placed on the transmission line) in a message, special hardware (like the NS DP83640.
The offset information reported by phc2sys shows the time offset between the PHC and the System clock. If phc2sys consistently reports offset lower than 100 ns, the System clock is synchronized. To verify the TAI offset set by the pmc command above has been correctly propagated to the kernel, read this offset value using the adjtimex() system call Offset and delay measurement—sync message, follow-up message The telegram propagation time is determined cyclically in a sec ond transmission process between the slave and the master (delay telegrams). The PTP protocol can be implemented completely in software using a standard Ethe rnet module Clause 6: PTP Clock Synchronization Model QUESTION: How do we take a collection of clocks, message types, clock properties, networks, etc. and produce MS_difference = offset + MS delay SM_difference = - offset + SM delay We get: offset = {(MS_difference - SM_difference) - (MS delay - S ~]# ptp4l -i eth3 -m selected eth3 as PTP clock port 1: INITIALIZING to LISTENING on INITIALIZE port 0: INITIALIZING to LISTENING on INITIALIZE port 1: new foreign master 00a069.fffe.0b552d-1 selected best master clock 00a069.fffe.0b552d port 1: LISTENING to UNCALIBRATED on RS_SLAVE master offset -23947 s0 freq +0 path delay 11350 master offset -28867 s0 freq +0 path delay 11236 master offset.
tux > sudo ptp4l -m -i eth0 selected eth0 as PTP clock port 1: INITIALIZING to LISTENING on INITIALIZE port 0: INITIALIZING to LISTENING on INITIALIZE port 1: new foreign master 00a152.fffe.0b334d-1 selected best master clock 00a152.fffe.0b334d port 1: LISTENING to UNCALIBRATED on RS_SLAVE master offset -25937 s0 freq +0 path delay 12340 master offset -27887 s0 freq +0 path delay 14232 master. (PTP 1-Step path delay measurement do not carry T2 back to the PDelay requester, for a accurate path delay measurement neighbor frequency offset is important) => another reason why gPTP use 2-Step Path Delay measurement ¾2-Step PathDealy measurement One & Two Ste 11) PTP two-step clock request-responsedelay measurement is performed repeatedly (t1, t2, t3, t4). WR Slave calculates M-to-S delay and clock offset and adjusts its time counters. A. WR Link Delay Model Sub-nanosecond synchronization requires a precise knowl-edge of one-way M-to-S delay (delay ms). PTP measures the round-trip delay (delay MM)
Hi, I am testing the Qbv scheduling and running the PTP synchronization using the below command. ptp4l -i eth0 -p /dev/ptp0 -m -l 7 -t 1000 But I am getting a huge delay most of the time. So, I want to set the NXP LS1021ATSN device as a. PTP (Precision Time Protocol) is the de facto protocol used by broadcasters, media network operators and service providers to synchronize device clocks in complex media networks to achieve accurately synchronized video, audio and meta-data streams. time. The DataMiner PTP app allows efficient 360° real-time monitoring of a PTP stack E2E和P2P上一篇文章介绍了1588的E2E链路延迟测量机制，本文顺带把P2P的链路延迟测量机制也一起介绍一下，这也便于以后介绍E2E透明时钟和P2P透明时钟。E2E就是End-to-End，它是由Slave clock发起的测量链路延迟的机制，而P2P（Peer-to-Peer）则是把每一个clock看作是对等的，每一个clock都会发起的链路延迟测量. Slave sends Delay Request frame to PTP Master and stores T3. Master sends Delay Response T4 time which is time of received T3. The adjustment for slave can be represented as: adj = -[(T2-T1) - (T4-T3)]/2. 从钟根据 t1 、 t2 、 t3 、 t4 计算时间偏移 (offset) 以及传输延时 ( delay) ,即 t2 -t1 = offset + delay t4 - t3 = delay. The master finally answers with a Delay_Response message (t 4). Having these four timestamps, the slave device can estimate the propagation delay and calculate its own offset from the master. The following formulas are used in the slave to establish the time at the master: Equation 1: PTP Delay and Offset calculatio
delay_filter Select the algorithm used to filter the measured delay and peer delay. 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),. Precision Time Protocol is used to synchronize clocks throughout the network. On a local area network, it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems. RouterOS supports IEEE 1588-2008, PTPv2. Support is hardware dependant, please see the supported device list below
Sync Xavier with PTP master. cuongm March 18, 2020, 10:41pm #1. I'm trying to time sync the system clock on the Jetson Xavier board with a PTP master without success. The PTP slave syncs OK with ptpv4l but the system clock couldn't converge (using phc2ys) ptp4l eth0 -m. ptp4l [17332.505]: selected /dev/ptp0 as PTP clock PTP assumes the path is symmetric in order to compute the time offset at the slave end. That is, Frequency transfer accuracy is impaired by transit delay variation, or PDV. The PTP slave device uses the interval of time between timestamps in PTP sync or follow-up packets to derive frequency synchronization
ideal alignment point for that frame rate is calculated based on the PTP epoch. Finally, the offset between the ST 2022-6 signal and the ideal alignment is displayed. The display shows both the absolute time and the time parsed into lines or horizontal delay as time and pixels. One use for the Timing application is to measure the delay in a gatewa Nov 11 16:18:04 arc-switch142 ptp4l: [3083.530] PTP [Debuggability]: PTP Grandmaster clock has changed from ec0d9a.fffe.603848 to 248a07.fffe.9e9adc Nov 11 16:18:04 arc-switch142 ptp4l: [3083.530] port 1: Interface Eth1/10 state changed from MASTER to UNCALIBRATED on RS_SLAVE Nov 11 16:18:05 arc-switch142 ptp4l: [3084.404] PTP slave port Eth1/10 High offset from Master -58705983752 (ns) Nov 11. ~]# ptp4l -i em3-m selected em3 as PTP clock port 1: INITIALIZING to LISTENING on INITIALIZE port 0: INITIALIZING to LISTENING on INITIALIZE port 1: new foreign master 00a069.fffe.0b552d-1 selected best master clock 00a069.fffe.0b552d port 1: LISTENING to UNCALIBRATED on RS_SLAVE master offset -23947 s0 freq +0 path delay 11350 master offset -28867 s0 freq +0 path delay 11236 master offset. PTPd Source Code Documentation. This is a brief overview of PTPd's source code intended to aid developers looking through PTPd. This documentation is incomplete, and it will be worked on as time permits. More information, particularly on PTPd's clock servo, is available in this paper written for the 2005 Conference on IEEE 1588.. The IEEE 1588 Precision Time Protoco Some PTP hardware clocks have a adjust phase mode that has a built-in hardware filtering capability. The adjust phase mode uses a phase offset control word instead of a frequency offset control word. Adjust phase support was introduced into the Linux PHC subsystem in Linux kernel v5.8
To generate the proper offset for the PTP timestamp at the CM output, the delay between the PTP input at the CMTS through the DOCSIS HFC network to the CM PTP output must be understood. In DOCSIS, the MAC protocol uses a ranging procedure to determine the timing offset of each CM from the CMTS, so that packets sent from CMs at different distances appear at the CMTS without overlapping timeslots # ntpq -p remote refid st t when poll reach delay offset jitter ===== *ns1.proserve.nl 193.67.79.202 2 u 21 64 377 31.420 10.742 3.689 -pomaz.hu 84.2.46.19 3 u 22 64 377 59.133 13.719 5.958 +server.104media 193.67.79.202 2 u 24 64 377 32.110 13.436 5.222 +public-timehost 193.11.166.20 2 u 28 64 377 57.214 9.304 6.311 # ntpstat synchronised to NTP server (80.84.224.85) at stratum 3 time correct.
IEEE® 1588 Precision Time Protocol (PTP) on the Offset and Delay Measurement — Sync Message, Follow-Up Message The telegram propagation time is determined cyclically in a sec ond transmission process between the slave and the master (delay telegrams) and the queue delay of the switches affected by network traffic. The following plots shown include the PTP Slave offset from the GPS Grandmaster (Figure 8) and the Histogram of the PTP Slave locked to the GPS Grandmaster (Figure 9). The Slave measured by the GPS time compare shows a 5.24 microseconds RM
The PTP protocol engine is able to select one of the available time stamp points as the source to calculate offset and delay. The synchro-nization behaviour and accuracy of different con. Large instantaneous delays cause large slave clock offset errors and are likely to be picked up by PTP slave daemons, so incremental delay over time must be used. Most of the intermediate nodes (Router1, Router2, Router3, Router4, TC1, TC2, and TC3) are points from which to launch a packet delay manipulation attack (red stars number 3, as shown in Fig. 2 ), for example —Round Trip Delay =25-10=15 —Clock Offset= [(T2-T1)-(T4-T3)]/2 —PTP profiles are created to allow organizations to specify selections of attribute values and optional features of PTP that, when using the same transport protocol, inter-works and achieve a performance that meets the requirements o In Hardware Timestamping, we are getting >1000 nanoseconds offset from the master which is far larger than the expected value of around 50 ns of PTP H/W Timestamping. For Software Timestamping, we are getting the expected offsets from the master which is <100 μs. Details of setup and execution This compensates for the delay and significantly improves the performance of the PTP network coexisting with other network traffic. Two step and One step In PTP, the most important issue is to determine the exact time at which the PTP Sync message is transmitted, which is received by the Ethernet interfaces of the slave clocks
Increase in bandwidth requirements on wireless backhaul networks and the need to reduce costs and to improve flexibility have triggered the need for a packet-based backhaul infrastructure. Traditional metro deployments do not cater to the delivery of synchronization services, and this leaves operators with no other choice than to keep older parallel infrastructure Andreas looks at how accurate RTP delivery is achieved, dealing with offset values, populating the timestamp from the PTP clock for realties streams and he explains how the playout delay is calculated from the link offset. Finally, he shows the relatively simple process of synchronisation art the playout device Sync and Delay_Req messages, time-stamping the arrival and departure times of each one (T1, T2, T3, and T4 in Figure 2). Figure 2 PTP Synchronization Messages The Follow_Up and Delay_Resp mes-sages convey precise T1 and T4 from the master to the slave. The slave uses T1, T2, T3, and T4 to cal-culate its offset and one-way delay rela Figure6 shows the output of the PTP demonstration. Results shows the offset and the path delay. It can be observed that after few seconds the LAN7430 tightly follows the GPS 1588 clock where the offset and the path delay are in single digit. FIGURE 6: LAN7430 PTP RESULT
PTP cannot distinguish changes in delay asymmetry from changes in clock offset between the Master and Slave. This is illustrated by an event that occurred outside the selected day. At approximately 23:43 the network latency between A and PTP Client uses Sync and Delay Response for PTP Synchronization. It includes 2 phases: 1) Offset correction (Difference between primary clock and client clock the Del_req_message equals the clock offset minus the transmission delay: Now the Slave clock is able to calculate both the clock offset and the transmission delay using both timestamp differences: Figure 1: PTP Message flow Master Slave 12:00 T 2 T 1 T 3 T 4 Offset M,S Sync Delay Request Delay Response Delay M,S Delay S,M Follow_u PTP primary and PTP secondary configuration are expected to satisfy only the O-DU side of requirements and provide the best-effort PTP primary for O-RU. Pre-configured Transport Delay Method: (time offset) Supported: Y: Y: N.
PTP Message Ethernet Header Client Data Field Ethernet FCS Ethernet Frame IP Data IP Header Offset . Bits header (13.3) receiveTimestamp requestingportldentity Offset Fallo,v Message Format Delay — Slave Clock .01 03 .02 (t4) Delay_Resp Propogation Delay Message Exchang The CPU goes through the complete IEEE 1588 procedure of exchanging PTP messages to calculate offset from the master. Note: The procedure of exchanging PTP messages is repeated several times and a packet delay variation (PDV) filtering algorithm is applied to filter out delay variation The slave updates its local time t with the estimated clock offset ^oms, see Equations (3) and (4). o^ms:= t2 t1 + ^ (3) t := t o^ms (4) PTP provides accuracy in the sub-microsecond range [1]. Problems in accuracy stem from the assumption of symmetrical delay, which when violated invalidates th One Way Delay Current value of one-way delay (or mean path delay) in seconds, calculated by PTPd in slave state from the Delay Request - Delay Response message exchange. Note: if this value remains at zero, this usually means that no Delay Response messages are being received, likely due to a network issue. Offset From Maste
Device# show ptp clock PTP CLOCK INFO PTP Device Type: Boundary clock PTP Device Profile: Default Profile Clock Identity: 0xCC:46:D6:FF:FE:C5:24:0 <<clock identity of this switch>> Clock Domain: 0 Number of PTP ports: 52 Priority1: 128 Priority2: 128 Clock Quality: Class: 248 Accuracy: Unknown Offset (log variance): 16640 Offset From Master(ns): 0 Mean Path Delay(ns): 0 Steps Removed: The PTP and NTP protocols have much in common; both develop four timestamps, although in different ways. These timestamps are used to compute the clock offset and roundtrip delay for a client relative to a server Sync Delay_Req t3 t2 t1 t4 Master clock time Slave clock time Introduction www.ti.com 1 Introduction Texas Instruments DP83640 precision PHYTER™ implements time-criticalportions of the IEEE 1588 Precision Time Protocol (PTP), allowing high precision IEEE 1588 node implementations 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
IEEE 1588v2 PTP Support. IEEE 1588v2 Precision Time Protocol (PTP) is a packet-based two-way message exchange protocol for synchronizing clocks between nodes in a network, thereby enabling an accurate time distribution over a network.This document explains how to configure IEEE 1588v2 PTP on the Cisco ASR 1002-X Routers Introduction: IEEE 1588 V2(Precise Time Protocol -PTP) Master time Slave time t 1 t 2 t 3 t 4 t‐ms t‐sm s y n c f oll o w _ u p d el a y _ r e s p d e l a y _ r e q t 2 t 1 t 2 t 1 t 2 t 3 t 1 t 2 t 3 t 4 Timestamps knownby slave Delay+Offset= t 2 -t 1 Delay‐Offset = t 4 -t 3 2 (t t ) (t t ) Delay = 2 − 1 + 4 − 3 2 (t t ) (t t. PTP Message types and rates Sync message, Follow -up, Announce, Delay_Request , and Delay_Response Fixed packet rate of 16 packets per second for Sync, Delay_Req and Delay_Resp messages for the case where physical layer frequency support (e.g. Synchronous Ethernet) is used The message rate for Announce message needs to be define offset (IEEE1588-2008 Annex L) Message Rates Sync & Follow-up Delay_request/response Announce Peer Delay_request/response Signaling Management ITU-T PTP Telecom Profile for Phase/Time (G.8275.1 Annex A) Time distribution to better than ±1.5 s ITU-T PTP profile for phase/time distribution with full timing support from the network. 1.0 00-19-A7.
path delay mechanism could be removed. This one-way operation mode is allowed by IEEE 1588-2019 and it is optional within ITU-T G.8265.1. PTP operation has to be compatible with existing telecommunication networks which may not in-clude specific support for PTP. Actually, it is as-sumed that the network may be completely unaware of PTP admin@N3550-F> config timesync ptp 0 Using PTP on management interface To check the status of the PTP timesync, use the show timesync command: admin@N3550-F> show timesync Sync method : ptp PTP domain : 0 PTP state : SLAVE Best master : 192.168.220.13 Last offset : 0.000000400 s Clock eth0 : state LOCKED, adev 2308.405000 Clock syst : state LOCKED, adev 61.97000 PTP协议里Offset和PathDelay的计算. 图片引自Cisco的文档 纠错: 标黄色的一个是t3, 一个是t4, 图上标错 Select the delay mechanism automatically. Start with E2E and switch to P2P whena peer delay request is received.-E Select the delay request-response (E2E) mechanism. This is the defaultmechanism. All clocks on single PTP communication path must use the samemechanism It is for sure that the GPS clock does not know the ingress latency of the. Endace card. According to the one of the GPS clock manufacturer, their egress latency. should be less than 100 ns. To sum up the installation of Linuxptp on Ubuntu: 1. Check the kernel version of Ubuntu by command uname -a
the PTP reference. time offset Alignment Point (AP), Epoch-Aware From Black Burst (Non-Epoch-Aware) VSYNC EXTRACT FROM SDI INPUT PTP EXTRACT AP Sender A Receiver Sender B Delay Response (t 4) Delay Response (t) PTP. Riedel Communications GmbH Co. KG Uellendahler Str. 210 Wuppertal Germany .riedel.ne The Video tab shows the Video-PTP offset which is a graphical plot of the Timing displays variation. The Video-RTP offset shows timing of the received signal relative to the embedded RTP time stamp. The Audio tab shows the Aud-Video offset that can indicate the amount of delay that must be applied to realign the signals
