Precision Time Protocol (PTP) provides time synchronization among devices with submicrosecond accuracy. It provides also precise frequency synchronization.

Basic concepts

PTP profile

PTP profiles (PTP standards) include:

· IEEE 1588 version 2—1588v2 defines high-accuracy clock synchronization mechanisms. It can be customized, enhanced, or tailored as needed. 1588v2 is the latest version.

· SMPTE ST 2059-2—ST2059-2 is introduced based on IEEE 1588. It specifies a profile specifically for the synchronization of audio or video equipment in a professional broadcast environment. It includes a self-contained description of parameters, their default values, and permitted ranges.

PTP domain

A PTP domain refers to a network that is enabled with PTP. A PTP domain has only one reference clock called "grandmaster clock (GM)." All devices in the domain synchronize to the clock.

Clock node and PTP port

A node in a PTP domain is a clock node. A port enabled with PTP is a PTP port. PTP defines the following types of basic clock nodes:

· Ordinary Clock (OC)—A PTP clock with a single PTP port in a PTP domain for time synchronization. It synchronizes time from its upstream clock node through the port. If an OC operates as the clock source, it sends synchronization time through a single PTP port to its downstream clock nodes.

· Boundary Clock (BC)—A clock with more than one PTP port in a PTP domain for time synchronization. A BC uses one of the ports to synchronize time from its upstream clock node. It uses the other ports to synchronize time to the relevant upstream clock nodes. If a BC operates as the clock source, such as BC 1 in Figure 1, it synchronizes time through multiple PTP ports to its downstream clock nodes.

· Transparent Clock (TC)—A TC does not keep time consistency with other clock nodes. A TC has multiple PTP ports. It forwards PTP messages among these ports and performs delay corrections for the messages, instead of performing time synchronization. TCs include the following types:

¡ End-to-End Transparent Clock (E2ETC)—Forwards non-P2P PTP packets in the network and calculates the delay of the entire link.

¡ Peer-to-Peer Transparent Clock (P2PTC)—Forwards only Sync, Follow_Up, and Announce messages, terminates other PTP messages, and calculates the delay of each link segment.

Figure 1 shows the positions of these types of clock nodes in a PTP domain.

Figure 1 Clock nodes in a PTP domain

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In addition to these basic types of clock nodes, PTP introduces hybrid clock nodes. For example, a TC+OC has multiple PTP ports in a PTP domain. One port is the OC type, and the others are the TC type.

A TC+OC forwards PTP messages through TC-type ports and performs delay corrections. In addition, it synchronizes time through its OC-type port. TC+OCs include these types: E2ETC+OC and P2PTC+OC.

Master-member/subordinate relationship

The master-member/subordinate relationship is automatically determined based on the Best Master Clock (BMC) algorithm. You can also manually specify a role for the clock nodes.

The master-member/subordinate relationship is defined as follows:

· Master/Member node—A master node sends a synchronization message, and a member node receives the synchronization message.

· Master/Member clock—The clock on a master node is a master clock (parent clock). The clock on a member node is a member clock.

· Master/Subordinate port—A master port sends a synchronization message, and a subordinate port receives the synchronization message. The master and subordinate ports can be on a BC or an OC.

A port that neither receives nor sends synchronization messages is a passive port.

Grandmaster clock

As shown in Figure 1, the clock nodes in a PTP domain are organized into a master-member hierarchy, where the GM operates as the reference clock for the entire PTP domain. Time synchronization is implemented through exchanging PTP messages.

Clock source

The clock nodes support the following clock sources:

· Local clock—38.88 MHz clock signals generated by a crystal oscillator inside the clock monitoring module.

· External clock—Clock signals generated by an external clock and received and sent by a 1PPS/ToD port on the MPU. The device sends the received signals to the clock monitoring module, which then sends them to all interface cards on the device. You can configure a time class and accuracy for an external clock.

Grandmaster clock selection and master-member/subordinate relationship establishment

A GM can be manually specified. It can also be elected through the BMC algorithm as follows:

1. The clock nodes in a PTP domain exchange announce messages and elect a GM by using the following rules in descending order:

a. Clock node with higher priority 1.

b. Clock node with higher time class.

c. Clock node with higher time accuracy.

d. Clock node with higher priority 2.

e. Clock node with a smaller port ID (containing clock number and port number).

The master nodes, member nodes, master ports, and subordinate ports are determined during the process. Then a spanning tree with the GM as the root is generated for the PTP domain.

2. The master node periodically sends announce messages to the member nodes. If the member nodes do not receive announce messages from the master node, they determine that the master node is invalid, and they start to elect another GM.

Synchronization mechanism

After master-member relationships are established between the clock nodes, the master and member clock nodes exchange PTP messages and record the message transmit and receive time. Based on the timestamps, each member clock calculates the path delay and time offset between them and the master clock and adjusts their time accordingly for time synchronization with the master clock.

PTP defines two path delay measurement mechanisms: Request_Response_ and Peer Delay, both of which are based on network symmetry.

Request_Response

The Request_Response mechanism measures the average path delay between the master and member clock nodes by using the PTP messages as shown in Figure 2. A TC between master and member clock nodes does not calculate the path delay. It forwards PTP messages and makes residence time correction on the Sync messages.

This mechanism can be implemented in one of the following two modes:

· Two-step mode—t1 is carried in the Follow_Up message as shown in Figure 2.

· Single-step mode—t1 is carried in the Sync message, and no Follow_Up message is sent.

Figure 2 shows the Request_Response mechanism in two-step mode.

1. The master clock sends a Sync message to the member clock, and records the sending time t1. Upon receiving the message, the member clock records the receiving time t2.

2. After sending the Sync message, the master clock immediately sends a Follow_Up message that carries time t1.

3. The member clock sends a Delay_Req message to the master clock, and records the sending time t3. Upon receiving the message, the master clock records the receiving time t4.

4. The master clock returns a Delay_Resp message that carries time t4.

After this procedure, the member clock obtains all the four timestamps and can make the following calculations:

· Round-trip delay between the master and member clocks: (t2 – t1) + (t4 – t3)

· One-way delay between the master and member clocks: [(t2 – t1) + (t4 – t3)] / 2

· Offset between the member and master clocks: (t2 – t1) – [(t2 – t1) + (t4 – t3)] / 2 or [(t2 – t1) – (t4 – t3)] / 2

Figure 2 Request_Response mechanism (two-step node)

Peer Delay

The Peer Delay mechanism measures the average path delay between two clock nodes by using Pdelay messages. The two clock nodes (BC, TC, or OC) using this mechanism send Pdelay messages to each other, and calculate the one-way link delay between them independently. The message interaction process and delay calculation method are identical on the two nodes. TCs that exist between master and member clock nodes divide the synchronization path into multiple links. Each TC makes link delay and residence time corrections on the Sync messages.

This mechanism can be implemented in one of the following two modes:

· Two-step mode

As shown in Figure 3, Pdelay messages include Pdelay_Req, Pdelay_Resp, and Pdelay_Resp_Follow_Up messages. t2 is carried in the Pdelay_Resp message, and t3 is carried in the Pdelay_Resp_Follow_Up message.

· Single-step mode:

Pdelay messages include Pdelay_Req and Pdelay_Resp messages. t3 – t2 is carried in the Pdelay_Resp, and no Pdelay_Resp_Follow_Up message is sent.

Figure 3 uses Clock node B as an example to describe the Peer Delay mechanism.

1. Clock node B sends a Pdelay_Req message to Clock node A, and records the sending time t1. Upon receiving the message, Clock node A records the receiving time t2.

2. Clock node A sends a Pdelay_Req message that carries t2 to Clock node B, and records the sending time t3. Upon receiving the message, Clock node B records the receiving time t4.

3. Clock node A immediately sends a Pdelay_Resp_Follow_Up message carrying t3 to Clock node B after sending the Pdelay_Req message.

After this procedure, Clock node B obtains all the four timestamps and can make the following calculations:

· Round-trip delay between Clock node A and Clock node B: (t2 – t1) + (t4 – t3)

· One-way delay between Clock node A and Clock node B: [(t2 – t1) + (t4 – t3)] / 2 = [(t3 – t2) + (t4 – t1)] / 2

· Time offset between the member clock and the master clock: Sync message receiving time on the member clock – Sync message sending time on the master clock – Total one-way delays on all links – Total PTP message residence time on all TCs.

Figure 3 Peer Delay mechanism (two-step mode)

Protocols and standards

· IEEE 1588-2008, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems

Restrictions and guidelines: PTP configuration

Before configuring PTP, determine the PTP profile and define the scope of the PTP domain and the role of every clock node.

PTP tasks at a glance

Configuring PTP (IEEE 1588 version 2)

1. Specifying PTP for obtaining the time

2. Specifying a PTP profile

Specify the IEEE 1588 version 2 PTP profile.

3. Configuring clock nodes

¡ Specifying a clock node type

¡ (Optional.) Configuring an OC to operate only as a member clock

4. (Optional.) Specifying a PTP domain

5. Enabling PTP on a port

6. Configuring PTP ports

¡ (Optional.) Configuring the role of a PTP port

¡ Configuring the mode for carrying timestamps

¡ Specifying a delay measurement mechanism for a BC or an OC

¡ Configuring one of the ports on a TC+OC clock as an OC-type port

7. (Optional.) Configuring PTP message transmission and receipt

¡ Setting the interval for sending announce messages and the timeout multiplier for receiving announce messages

¡ Setting the interval for sending Pdelay_Req messages

¡ Setting the interval for sending Sync messages

¡ Setting the minimum interval for sending Delay_Req messages

8. (Optional.) Configuring parameters for PTP messages

¡ Specifying the protocol for encapsulating PTP messages as UDP

¡ Configuring a source IP address for multicast PTP message transmission over UDP

¡ Configuring a destination IP address for unicast PTP message transmission over UDP Configuring a destination IP address for

¡ Configuring the MAC address for non-Pdelay messages

¡ Setting a DSCP value for PTP messages transmitted over UDP

¡ Specifying a VLAN tag for PTP messages

9. (Optional.) Adjusting and correcting clock synchronization

¡ Setting the delay correction value

¡ Setting the cumulative offset between UTC and TAI

¡ Setting the correction date of the UTC

10. (Optional.) Configuring a priority for a clock

Configuring PTP (SMPTE ST 2059-2)

1. Specifying PTP for obtaining the time

2. Specifying a PTP profile

Specify the SMPTE ST 2059-2 PTP profile.

3. Configuring clock nodes

¡ Specifying a clock node type

¡ (Optional.) Configuring an OC to operate only as a member clock

4. (Optional.) Specifying a PTP domain

5. Enabling PTP on a port

6. Configuring PTP ports

¡ (Optional.) Configuring the role of a PTP port

¡ Configuring the mode for carrying timestamps

¡ Specifying a delay measurement mechanism for a BC or an OC

7. (Optional.) Configuring PTP message transmission and receipt

¡ Setting the interval for sending announce messages and the timeout multiplier for receiving announce messages

¡ Setting the interval for sending Pdelay_Req messages

¡ Setting the interval for sending Sync messages

¡ Setting the minimum interval for sending Delay_Req messages

8. (Optional.) Configuring parameters for PTP messages

¡ Configuring a source IP address for multicast PTP message transmission over UDP

¡ Configuring a destination IP address for unicast PTP message transmission over UDP

¡ Setting a DSCP value for PTP messages transmitted over UDP

¡ Specifying a VLAN tag for PTP messages

9. (Optional.) Adjusting and correcting clock synchronization

¡ Setting the delay correction value

¡ Setting the cumulative offset between UTC and TAI

¡ Setting the correction date of the UTC

10. (Optional.) Configuring a priority for a clock

Specifying PTP for obtaining the time

1. Enter system view.

system-view

2. Specify PTP for obtaining the time.

clock protocol ptp

By default, the device uses NTP to synchronize the system time.

For more information about the clock protocol command, see device management commands in Fundamentals Command Reference.

Specifying a PTP profile

Restrictions and guidelines

You must specify a PTP profile before configuring PTP settings. Changing the PTP profile clears all settings under the profile.

Procedure

1. Enter system view.

system-view

2. Specify a PTP profile.

ptp profile { 1588v2 | st2059-2 }

By default, no PTP profile is configured, and PTP is not running on the device.

Configuring clock nodes

Specifying a clock node type

Restrictions and guidelines

You can specify only one clock node type for the device. The clock node types include OC, BC, E2ETC, P2PTC, E2ETC+OC, and P2PTC+OC.

Before you specify a clock node type, specify a PTP profile.

For the SMPTE ST 2059-2 PTP profile, you cannot specify the E2ETC+OC or P2PTC+OC clock node type.

Changing or removing the clock node type restores the default settings of the PTP profile.

Procedure

1. Enter system view.

system-view

2. Specify a clock node type for the device.

ptp mode { bc | e2etc | e2etc-oc | oc | p2ptc | p2ptc-oc }

By default, no clock node type is specified.

Configuring an OC to operate only as a member clock

About configuring an OC to operate only as a member clock

An OC can operate either as a master clock to send synchronization messages or as a member clock to receive synchronization messages. This task allows you to configure an OC to operate only as a member clock.

If an OC is operating only as a member clock, you can use the ptp force-state command to configure its PTP port as a master port or passive port.

Restrictions and guidelines

This task is applicable only to OCs.

Procedure

1. Enter system view.

system-view

2. Configure the OC to operate only as a member clock.

ptp slave-only

By default, an OC operates as a master or member clock.

Specifying a PTP domain

About PTP domains

Within a PTP domain, all devices follow the same rules to communicate with each other. Devices in different PTP domains cannot exchange PTP messages.

Procedure

1. Enter system view.

system-view

2. Specify a PTP domain for the device.

ptp domain value

The default setting varies by PTP profile:

¡ IEEE 1588 version 2—The device is in PTP domain 0.

¡ SMPTE ST 2059-2—The device is in PTP domain 127.

Enabling PTP on a port

About enabling PTP on a port

A port enabled with PTP becomes a PTP port.

Restrictions and guidelines

You can enable PTP on only one port on an OC.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Enable PTP on the port.

ptp enable

By default, PTP is disabled on a port.

Configuring PTP ports

Configuring the role of a PTP port

About configuring the role of a PTP port

You can configure the master, passive, or slave role for a PTP port.

For an OC that operates in slave-only mode, you can perform this task to change its PTP port role to master or slave.

Restrictions and guidelines

By default, the PTP port roles are automatically computed by the BMC algorithm. If you use this command to forcibly modify the role of a PTP port, all the other PTP ports in the PTP domain stop working and you must specify a role for each of them manually. As a best practice, enable the device to use the BMC algorithm to determine the roles of PTP ports.

You can specify only one slave port on the device.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure the role of the PTP port.

ptp force-state { master | passive | slave }

By default, the PTP port role is automatically calculated through BMC.

4. Return to system view.

quit

5. Activate the port role configuration.

ptp active force-state

By default, the port role configuration is not activated.

Configuring the mode for carrying timestamps

About the mode for carrying timestamps

Timestamps can be carried in either of the following modes:

· Single-step mode—The following messages contain the message sending time:

¡ Sync message in the Request_Response and Peer Delay mechanisms.

¡ Pdelay_Resp message in the Peer Delay mechanism.

· Two-step mode—All messages contain the message sending time, except for the following messages:

¡ Sync message in the Request_Response and Peer Delay mechanisms.

¡ Pdelay_Resp message in the Peer Delay mechanism.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure the mode for carrying timestamps.

ptp clock-step { one-step | two-step }

By default, the two-step mode is used for carrying timestamps.

Specifying a delay measurement mechanism for a BC or an OC

About the delay measurement mechanism

PTP defines two transmission delay measurement mechanisms: Request_Response and Peer Delay. For correct communication, ports on the same link must share the same delay measurement mechanism.

The delay measurement mechanism is Request_Response for E2ETCs and E2ETC+OCs and Peer Delay for P2PTCs and P2PTC+OCs. You cannot change the delay measurement mechanism for these clock nodes

Restrictions and guidelines

This task is applicable only to BCs and OCs.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Specify a delay measurement mechanism for a BC or an OC.

ptp delay-mechanism { e2e | p2p }

The default delay measurement mechanism depends on the PTP profile.

Configuring one of the ports on a TC+OC clock as an OC-type port

About configuring one of the ports on a TC+OC clock as an OC-type port

All ports on a TC+OC (E2ETC+OC or P2PTC+OC) are TC-type ports by default. This feature allows you to configure one of the ports on a TC+OC clock as an OC-type port.

Restrictions and guidelines

This task is applicable only to E2ETC+OCs and P2PTC+OCs.

This task is not available for the SMPTE ST 2059-2 PTP profile.

When a TC+OC is synchronizing time to a downstream clock node through a TC-type port, prevent it from synchronizing with the downstream clock node through an OC-type port.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure the port type as OC.

ptp port-mode oc

By default, the port type for all ports on a TC+OC is TC.

Configuring PTP message transmission and receipt

Setting the interval for sending announce messages and the timeout multiplier for receiving announce messages

About the interval for sending announce messages and the timeout multiplier for receiving announce messages

A master node periodically sends announce messages to the member nodes. If a member node does not receive any announce messages from the master node before the timeout timer expires, it determines that the master node is invalid.

The timeout timer for receiving announce messages is the announce message sending interval configured on the member node × timeout multiplier. The timeout multiplier is the number of announce message sending intervals that the member device will wait for receiving an announce message before a timeout occurs.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set the interval for sending announce messages.

ptp announce-interval interval

The default settings vary by PTP profile.

¡ IEEE 1588 version 2—The interval argument value is 1 and the interval for sending announce messages is 2 (21) seconds.

¡ SMPTE ST 2059-2—The interval argument value is –2 and the interval for sending announce messages is 1/4 (2-2) seconds.

4. Set a timeout multiplier of the announce message sending interval.

ptp announce-timeout multiple-value

By default, the timeout multiplier of the announce message sending interval is 3.

Setting the interval for sending Pdelay_Req messages

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set the interval for sending Pdelay_Req messages.

ptp pdelay-req-interval interval

By default, the interval argument value is 0 and the interval for sending peer delay request messages is 1 (20) second.

For the SMPTE ST 2059-2 PTP profile, set the interval argument to a value in the range of ptp syn-interval interval to ptp syn-interval interval plus 5 as a best practice.

Setting the interval for sending Sync messages

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set the interval for sending Sync messages.

ptp syn-interval interval

The default settings vary by PTP profile.

¡ IEEE 1588 version 2—The interval argument value is 0 and the interval for sending Sync messages is 1 (20) second.

¡ SMPTE ST 2059-2—The interval argument value is –3 and the interval for sending Sync messages is 1/8 (2-3) seconds.

Setting the minimum interval for sending Delay_Req messages

About the minimum interval for sending Delay_Req messages

When receiving a Sync or Follow_Up message, an interface can send Delay_Req messages only when the minimum interval is reached. This task allows you to set the minimum interval for sending Delay_Req messages.

Restrictions and guidelines

In PTP multicast transport mode, this command takes effect only when configured on the master clock. The master clock sends the value to a member clock through PTP messages to control the interval for the member clock to send Delay_Req messages. To view the interval, execute the display ptp interface command on the member clock.

In PTP unicast transport mode, this command takes effect when configured on member clocks. It does not take effect when configured on the master clock.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set the minimum interval for sending Delay_Req messages.

ptp min-delayreq-interval interval

By default, the interval argument value is 0 and the minimum interval for sending delay request messages is 1 (20) second.

For the SMPTE ST 2059-2 PTP profile, set the interval argument to a value in the range of ptp syn-interval interval to ptp syn-interval interval plus 5 as a best practice.

Configuring parameters for PTP messages

Specifying the protocol for encapsulating PTP messages as UDP

About PTP message encapsulation protocols

PTP messages can be encapsulated in IEEE 802.3/Ethernet packets or UDP packets.

Restrictions and guidelines

For the SMPTE ST 2059-2 PTP profile, PTP messages can be encapsulated only in UDP packets. This task is not available for the SMPTE ST 2059-2 PTP profile.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure the protocol for encapsulating PTP messages as UDP.

ptp transport-protocol udp

By default, PTP messages are encapsulated in IEEE 802.3/Ethernet packets.

Configuring a source IP address for multicast PTP message transmission over UDP

About configuring a source IP address for multicast PTP message transmission over UDP

To transport multicast PTP messages over UDP, you must configure a source IP address for the messages.

Restrictions and guidelines

If both a source IP address for multicast PTP message transmission over UDP and a destination address for unicast PTP message transmission over UDP are configured, the system unicasts the messages.

Procedure

1. Enter system view.

system-view

2. Configure a source IP address for multicast PTP message transmission over UDP.

ptp source ip-address [ vpn-instance vpn-instance-name ]

By default, no source IP address is configured for multicast PTP message transmission over UDP.

Configuring a destination IP address for unicast PTP message transmission over UDP

About configuring a destination IP address for unicast PTP message transmission over UDP

To transport unicast PTP messages over UDP, you must configure a destination IP address for the messages.

Restrictions and guidelines

If both a source IP address for multicast PTP message transmission over UDP and a destination address for unicast PTP message transmission over UDP are configured, the system unicasts the messages.

Prerequisites

Configure an IP address for the current interface, and make sure the interface and the peer PTP interface can reach each other.

Procedure

1. Enter system view.

system-view

2. Enter Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure a destination IP address for unicast PTP message transmission over UDP.

ptp unicast-destination ip-address

By default, no destination IP address is configured for unicast PTP message transmission over UDP.

Configuring the MAC address for non-Pdelay messages

About the MAC address for non-Pdelay messages

Pdelay messages include Pdelay_Req, Pdelay_Resp, and Pdelay_Resp_Follow_Up messages. The destination MAC address of Pdelay messages is 0180-C200-000E by default, which cannot be modified. The destination MAC address of non-Pdelay messages is either 0180-C200-000E or 011B-1900-0000.

Restrictions and guidelines

This feature takes effect only when PTP messages are encapsulated in IEEE 802.3/Ethernet packets.

This task is not available for the SMPTE ST 2059-2 PTP profile.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Configure the destination MAC address for non-Pdelay messages.

ptp destination-mac mac-address

The default destination MAC address is 011B-1900-0000.

Setting a DSCP value for PTP messages transmitted over UDP

About DSCP values for PTP messages

The DSCP value determines the sending precedence of PTP messages transmitted over UDP.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set a DSCP value for PTP messages transmitted over UDP.

ptp dscp dscp

By default, the DSCP value is 56.

Specifying a VLAN tag for PTP messages

About specifying a VLAN tag for PTP messages

Perform this task to configure the VLAN ID and the 802.1p precedence in the VLAN tag carried by PTP messages.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view.

interface interface-type interface-number

3. Specify a VLAN tag for PTP messages.

ptp vlan vlan-id [ dot1p dot1p-value ]

By default, PTP messages do not have a VLAN tag.

Adjusting and correcting clock synchronization

Setting the delay correction value

About setting the delay correction value

PTP performs time synchronization based on the assumption that the delays in sending and receiving messages are the same. However, this is not practical. If you know the offset between the delays in sending and receiving messages, you can set the delay correction value for more accurate time synchronization.

Procedure

1. Enter system view.

system-view

2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.

interface interface-type interface-number

3. Set a delay correction value.

ptp asymmetry-correction { minus | plus } value

The default is 0 nanoseconds. Delay correction is not performed.

Setting the cumulative offset between UTC and TAI

About setting the cumulative offset between UTC and TAI

An offset exists between Coordinated Universal Time (UTC) and International Atomic Time (TAI). The device displays the UTC time. However, PTP uses TAI for time synchronization. For the device to synchronize correct time to other clock nodes in the PTP domain when its local clock is selected as the GM, configure this command to correct the offset between UTC and TAI.

Procedure

1. Enter system view.

system-view

2. Set the cumulative offset between UTC and TAI.

ptp utc offset utc-offset

The default is 0 seconds.

Setting the correction date of the UTC

About setting the correction date of the UTC

This task allows you to adjust the UTC at the last minute (23:59) of the specified date.

Restrictions and guidelines

If you configure the setting multiple times, the most recent configuration takes effect.

This setting takes effect only when it is configured on the master clock node and the local clock of the master clock node is the GM.

Procedure

1. Enter system view.

system-view

2. Set the correction date of the UTC.

ptp utc { leap59-date | leap61-date } date

By default, the correction date of the UTC is not configured.

Configuring a priority for a clock

About configuring a priority for a clock

Priorities for clocks are used to elect the GM. The smaller the priority value, the higher the priority.

Procedure

1. Enter system view.

system-view

2. Configure the priority for the specified clock for GM election through BMC.

ptp priority clock-source local { priority1 priority1 | priority2 priority2 }

By default, both the priority 1 and priority 2 values are 128.

Display and maintenance commands for PTP

Execute display commands in any view and the reset command in user view.

Task	Command
Display PTP clock information.	display ptp clock
Display the delay correction history.	display ptp corrections
Display information about foreign master nodes.	display ptp foreign-masters-record [ interface interface-type interface-number ]
Display PTP information on an interface.	display ptp interface [ interface-type interface-number \| brief ]
Display parent node information for the PTP device.	display ptp parent
Display PTP statistics.	display ptp statistics [ interface interface-type interface-number ]
Display PTP clock time properties.	display ptp time-property
Clear PTP statistics.	reset ptp statistics [ interface interface-type interface-number ]

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PTP configuration examples

Example: Configuring PTP configuration (IEEE 1588 version 2, IEEE 802.3/Ethernet encapsulation)

Network configuration

As shown in Figure 4, a PTP domain contains Device A, Device B, and Device C.

· Configure all devices to use the IEEE 1588 version 2 PTP profile.

· Configure PTP messages to be encapsulated in IEEE 802.3/Ethernet packets.

· Specify the OC clock node type for Device A and Device C, and E2ETC clock node type for Device B. All clock nodes elect a GM through BMC based on their respective default GM attributes.

Figure 4 Network diagram

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Procedure

1. Configure Device A:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceA> system-view

[DeviceA] ptp profile 1588v2

# Specify the OC clock node type.

[DeviceA] ptp mode oc

# Specify PTP for obtaining the time.

[DeviceA] clock protocol ptp

# Enable PTP on Ten-GigabitEthernet 1/0/1.

[DeviceA] interface ten-gigabitethernet 1/0/1

[DeviceA-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceA-Ten-GigabitEthernet1/0/1] quit

2. Configure Device B:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceB> system-view

[DeviceB] ptp profile 1588v2

# Specify the E2ETC clock node type.

[DeviceB] ptp mode e2etc

# Specify PTP for obtaining the time.

[DeviceB] clock protocol ptp

# Enable PTP on Ten-GigabitEthernet 1/0/1.

[DeviceB] interface ten-gigabitethernet 1/0/1

[DeviceB-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/1] quit

# Enable PTP on Ten-GigabitEthernet 1/0/2.

[DeviceB] interface ten-gigabitethernet 1/0/2

[DeviceB-Ten-GigabitEthernet1/0/2] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/2] quit

3. Configure Device C:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceC> system-view

[DeviceC] ptp profile 1588v2

# Specify the OC clock node type.

[DeviceC] ptp mode oc

# Specify PTP for obtaining the time.

[DeviceC] clock protocol ptp

# Enable PTP on Ten-GigabitEthernet 1/0/1.

[DeviceC] interface ten-gigabitethernet 1/0/1

[DeviceC-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceC-Ten-GigabitEthernet1/0/1] quit

Verifying the configuration

When the network is stable, perform the following tasks to verify that Device A is elected as the GM, Ten-GigabitEthernet1/0/1 on Device A is the master port, and Device B has synchronized to Device A:

· Use the display ptp clock command to display PTP clock information.

· Use the display ptp interface brief command to display brief PTP statistics on an interface.

# Display PTP clock information on Device A.

[DeviceA] display ptp clock

PTP profile : IEEE 1588 Version 2

PTP mode : OC

Slave only : No

Clock ID : 000FE2-FFFE-FF0000

Clock type : Local

Clock domain : 0

Number of PTP ports : 1

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : 0 (ns)

Mean path delay : 0 (ns)

Steps removed : 0

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device A.

[DeviceA] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

XGE1/0/1 Master E2E Two 0

# Display PTP clock information on Device B.

[DeviceB] display ptp clock

PTP profile : IEEE 1588 Version 2

PTP mode : E2ETC

Slave only : No

Clock ID : 000FE2-FFFE-FF0001

Clock type : Local

Clock domain : 0

Number of PTP ports : 2

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : N/A

Mean path delay : N/A

Steps removed : N/A

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device B.

[DeviceB] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

XGE1/0/1 N/A E2E Two 0

XGE1/0/2 N/A E2E Two 0

Example: Configuring PTP (IEEE 1588 version 2, multicast transmission)

Network configuration

As shown in Figure 5, a PTP domain contains Device A, Device B, and Device C.

· Configure all devices to use the IEEE 1588 version 2 PTP profile.

· Configure the source IP address for multicast PTP message transmission over UDP.

· Specify the OC clock node type for Device A and Device C, and the P2PTC clock node type for Device B. All clock nodes elect a GM through BMC based on their respective default GM attributes.

· Configure the peer delay measurement mechanism (p2p) for Device A and Device C.

Figure 5 Network diagram

‌

Procedure

1. Configure Device A:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceA> system-view

[DeviceA] ptp profile 1588v2

# Specify the OC clock node type.

[DeviceA] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceA] ptp source 10.10.10.1

# Specify PTP for obtaining the time.

[DeviceA] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, specify the PTP transport protocol as UDP, specify the delay measurement mechanism as p2p, and enable PTP.

[DeviceA] interface ten-gigabitethernet 1/0/1

[DeviceA-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp [DeviceA-Ten-GigabitEthernet1/0/1] ptp delay-mechanism p2p

[DeviceA-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceA-Ten-GigabitEthernet1/0/1] quit

2. Configure Device B:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceB> system-view

[DeviceB] ptp profile 1588v2

# Specify the P2PTC clock node type.

[DeviceB] ptp mode p2ptc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceB] ptp source 10.10.10.2

# Specify PTP for obtaining the time.

[DeviceB] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, specify the PTP transport protocol as UDP and enable PTP.

[DeviceB] interface ten-gigabitethernet 1/0/1

DeviceB-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp

[DeviceB-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/1] quit

# On Ten-GigabitEthernet 1/0/2, specify the PTP transport protocol as UDP and enable PTP.

[DeviceB] interface ten-gigabitethernet 1/0/2

[DeviceB-Ten-GigabitEthernet1/0/2] ptp transport-protocol udp

[DeviceB-Ten-GigabitEthernet1/0/2] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/2] quit

3. Configure Device C:

# Specify the IEEE 1588 version 2 PTP profile.

<DeviceC> system-view

[DeviceC] ptp profile 1588v2

# Specify the OC clock node type.

[DeviceC] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceC] ptp source 10.10.10.3

# Specify PTP for obtaining the time.

[DeviceC] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, specify the PTP transport protocol as UDP, specify the delay measurement mechanism as p2p, and enable PTP.

[DeviceC] interface ten-gigabitethernet 1/0/1

[DeviceC-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp [DeviceC-Ten-GigabitEthernet1/0/1] ptp delay-mechanism p2p

[DeviceC-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceC-Ten-GigabitEthernet1/0/1] quit

Verifying the configuration

· Use the display ptp clock command to display PTP clock information.

· Use the display ptp interface brief command to display brief PTP statistics on an interface.

# Display PTP clock information on Device A.

[DeviceA] display ptp clock

PTP profile : IEEE 1588 Version 2

PTP mode : OC

Slave only : No

Clock ID : 000FE2-FFFE-FF0000

Clock type : Local

Clock domain : 0

Number of PTP ports : 1

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : 0 (ns)

Mean path delay : 0 (ns)

Steps removed : 0

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device A.

[DeviceA] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

XGE1/0/1 Master P2P Two 0

# Display PTP clock information on Device B.

[DeviceB] display ptp clock

PTP profile : IEEE 1588 Version 2

PTP mode : P2PTC

Slave only : No

Clock ID : 000FE2-FFFE-FF0001

Clock type : Local

Clock domain : 0

Number of PTP ports : 2

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : N/A

Mean path delay : N/A

Steps removed : N/A

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device B.

[DeviceB] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

XGE1/0/1 N/A P2P Two 0

XGE1/0/2 N/A P2P Two 0

Example: Configuring PTP (SMPTE ST 2059-2, multicast transmission)

Network configuration

As shown in Figure 6, Device A, Device B, and Device C are in a PTP domain. Configure PTP (SMPTE ST 2059-2, multicast transmission) on the three devices as follows for time synchronization:

· Configure the devices to use the SMPTE ST 2059-2 PTP profile.

· Configure the source IP address for multicast PTP message transmission over UDP.

· Specify the OC clock node type for Device A and Device C, and the P2PTC clock node type for Device B. All clock nodes elect a GM through BMC based on their respective default GM attributes.

· Configure the peer delay measurement mechanism (p2p) for Device A and Device C.

Figure 6 Network diagram

‌

Procedure

1. Configure Device A:

# Specify the SMPTE ST 2059-2 PTP profile.

<DeviceA> system-view

[DeviceA] ptp profile st2059-2

# Specify the OC clock node type.

[DeviceA] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceA] ptp source 10.10.10.1

# Specify PTP for obtaining the time.

[DeviceA] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, specify the delay measurement mechanism as p2p and enable PTP.

[DeviceA] interface ten-gigabitethernet 1/0/1

[DeviceA-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp [DeviceA-Ten-GigabitEthernet1/0/1] ptp delay-mechanism p2p

[DeviceA-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceA-Ten-GigabitEthernet1/0/1] quit

2. Configure Device B:

# Specify the SMPTE ST 2059-2 PTP profile.

<DeviceB> system-view

[DeviceB] ptp profile st2059-2

# Specify the P2PTC clock node type.

[DeviceB] ptp mode p2ptc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceB] ptp source 10.10.10.2

# Specify PTP for obtaining the time.

[DeviceB] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, enable PTP.

[DeviceB] interface ten-gigabitethernet 1/0/1

DeviceB-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp

[DeviceB-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/1] quit

# On Ten-GigabitEthernet 1/0/2, enable PTP.

[DeviceB] interface ten-gigabitethernet 1/0/2

[DeviceB-Ten-GigabitEthernet1/0/2] ptp transport-protocol udp

[DeviceB-Ten-GigabitEthernet1/0/2] ptp enable

[DeviceB-Ten-GigabitEthernet1/0/2] quit

3. Configure Device C:

# Specify the SMPTE ST 2059-2 PTP profile.

<DeviceC> system-view

[DeviceC] ptp profile st2059-2

# Specify the OC clock node type.

[DeviceC] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over UDP.

[DeviceC] ptp source 10.10.10.3

# Specify PTP for obtaining the time.

[DeviceC] clock protocol ptp

# On Ten-GigabitEthernet 1/0/1, specify the delay measurement mechanism as p2p and enable PTP.

[DeviceC] interface ten-gigabitethernet 1/0/1

[DeviceC-Ten-GigabitEthernet1/0/1] ptp transport-protocol udp [DeviceC-Ten-GigabitEthernet1/0/1] ptp delay-mechanism p2p

[DeviceC-Ten-GigabitEthernet1/0/1] ptp enable

[DeviceC-Ten-GigabitEthernet1/0/1] quit

Verifying the configuration

When the network is stable, perform the following tasks to verify the PTP configuration:

· Use the display ptp clock command to display PTP clock information.

· Use the display ptp interface brief command to display brief PTP statistics on an interface.

# Display PTP clock information on Device A.

[DeviceA] display ptp clock

PTP profile : SMPTE ST 2059-2

PTP mode : OC

Slave only : No

Clock ID : 000FE2-FFFE-FF0000

Clock type : Local

Clock domain : 0

Number of PTP ports : 1

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : 0 (ns)

Mean path delay : 0 (ns)

Steps removed : 0

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device A.

[DeviceA] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

GE1/0/1 Master P2P Two 0

# Display PTP clock information on Device B.

[DeviceB] display ptp clock

PTP profile : SMPTE ST 2059-2

PTP mode : P2PTC

Slave only : No

Clock ID : 000FE2-FFFE-FF0001

Clock type : Local

Clock domain : 0

Number of PTP ports : 2

Priority1 : 128

Priority2 : 128

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 65535

Offset from master : N/A

Mean path delay : N/A

Steps removed : N/A

Local clock time : Sun Jan 15 20:57:29 2011

# Display brief PTP statistics on Device B.

[DeviceB] display ptp interface brief

Name State Delay mechanism Clock step Asymmetry correction

GE1/0/1 N/A P2P Two 0

GE1/0/2 N/A P2P Two 0

The output shows that Device A is elected as the GM and Ten-GigabitEthernet1/0/1 on Device A is the master port.

11-Network Management and Monitoring Configuration Guide

Basic concepts

PTP profile

PTP domain

Clock node and PTP port

Master-member/subordinate relationship

Grandmaster clock

Clock source

Request_Response

Peer Delay

Specifying PTP for obtaining the time

Specifying a PTP profile

Restrictions and guidelines

Procedure

Restrictions and guidelines

Configuring an OC to operate only as a member clock

About configuring an OC to operate only as a member clock

Restrictions and guidelines

Procedure

About PTP domains

Procedure

About enabling PTP on a port

Restrictions and guidelines

Procedure

About configuring the role of a PTP port

Restrictions and guidelines

Procedure

About the mode for carrying timestamps

Procedure

About the delay measurement mechanism

Restrictions and guidelines

Procedure

About configuring one of the ports on a TC+OC clock as an OC-type port

Restrictions and guidelines

Procedure

Configuring PTP message transmission and receipt

Setting the interval for sending announce messages and the timeout multiplier for receiving announce messages

About the interval for sending announce messages and the timeout multiplier for receiving announce messages

Procedure

About the minimum interval for sending Delay_Req messages

Restrictions and guidelines

Procedure

About PTP message encapsulation protocols

Restrictions and guidelines

Procedure

Configuring a source IP address for multicast PTP message transmission over UDP

About configuring a source IP address for multicast PTP message transmission over UDP

Restrictions and guidelines

Procedure

Configuring a destination IP address for unicast PTP message transmission over UDP

About configuring a destination IP address for unicast PTP message transmission over UDP

Restrictions and guidelines

Prerequisites

Procedure

About the MAC address for non-Pdelay messages

Restrictions and guidelines

Procedure

Setting a DSCP value for PTP messages transmitted over UDP

About DSCP values for PTP messages

Procedure

About specifying a VLAN tag for PTP messages

Procedure

About setting the delay correction value

Procedure

About setting the cumulative offset between UTC and TAI

Procedure

About setting the correction date of the UTC

Restrictions and guidelines

Procedure

About configuring a priority for a clock

Procedure

Example: Configuring PTP configuration (IEEE 1588 version 2, IEEE 802.3/Ethernet encapsulation)

Network configuration

Procedure

Verifying the configuration

Network configuration

Procedure

Verifying the configuration

Network configuration

Procedure