Precision Time Protocol (PTP) synchronizes time among devices. It provides greater accuracy than other time synchronization protocols such as NTP. It can also be used for frequency synchronization. For more information about NTP, see "Configuring NTP."

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.

· IEEE 802.1AS—802.1AS is introduced based on IEEE 1588. It specifies a profile for use of IEEE 1588-2008 for time synchronization over a virtual bridged local area network (as defined by IEEE 802.1Q). 802.1AS supports point-to-point full-duplex Ethernet, IEEE 802.11, and IEEE 802.3 EPON links.

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

Besides the three 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, but you must activate the PTP port role configuration to make the master-member/subordinate relationship take effect.

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.

A GM can be manually configured, or it can be elected through the BMC algorithm by following this procedure:

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.

Local clock

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

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 carries the Sync message residence time on it to the downstream clock node.

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. The two clock nodes (BC, TC, or OC) implementing 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 and participate in delay calculation. The link delays and Sync message residence time on the TCs are carried to downstream nodes.

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 = [(t4 – t1) -(t3 – t2)] / 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 Sync 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

· IEEE P802.1AS, Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks

Compatibility information

Feature and hardware compatibility

The PTP feature is supported only on the following devices:

· S6800-54HF switch

· S6800-54HT switch

· S6800-2C-FC switch

· Switches labeled with the following product codes:

¡ LS-6800-32Q-H1

¡ LS-6800-54QF-H1

¡ LS-6800-54QT-H1

¡ LS-6800-2C-H1

¡ LS-6800-4C-H1

¡ LS-6800-54QF-H3

¡ LS-6800-54QT-H3

Feature and software version compatibility

The PTP feature is available in R2612 and later.

Restrictions and guidelines

In a PTP domain that runs the IEEE 1588 version 2 or IEEE 802.1AS PTP profile, specify the BC or OC clock node type for the devices in the domain as a best practice. A TC clock node is mainly used for forwarding PTP messages. When receiving a PTP message, a TC multicasts the message from all its PTP interfaces except the inbound interface of the PTP message. To deploy a TC in the domain, plan the TC location and number and location of PTP interfaces on the TC manually to prevent PTP forwarding loops.

Configuration task list

Before performing the following configurations, define the scope of the PTP domain and the role of every clock node.

Tasks at a glance
(Required.) Configuring PTP Specifying a PTP standard
The PTP standard is IEEE 1588 version 2: (Required.) Specifying a clock node type (Optional.) Specifying a PTP domain (Optional.) Configuring an OC to operate only as a member clock (Optional.) Configuring the role of a PTP port (Optional.) Specifying a delay measurement mechanism for a BC or an OC (Optional.) Configuring the port type for a TC+OC (Optional.) Setting the interval for sending announce messages and the interval timeout (Optional.) Setting the interval for sending Pdelay_Req messages (Optional.) Setting the interval for sending Sync messages (Optional.) Setting the minimum interval for sending Delay_Req messages (Optional.) Configuring the MAC address for non-pdelay messages (Optional.) Specifying the IPv4 UDP transport protocol for PTP messages (Optional.) Configuring the source IP address for multicast PTP message transmission over (Optional.) Configuring the destination IP address for unicast PTP message transmission over (Optional.) Setting the delay correction value (Optional.) Setting the cumulative offset between the UTC and TAI (Optional.) Setting the correction date of the UTC (Optional.) Configuring a priority for a clock (Optional.) Setting a DSCP value for PTP messages transmitted over (Optional.) Specifying a VLAN tag for PTP messages (Optional.) Specifying the system time protocol as PTP (Required.) Enabling PTP on a port
The PTP standard is IEEE 802.1AS (802.1AS): (Required.) Specifying a clock node type (Optional.) Specifying a PTP domain (Optional.) Configuring an OC to operate only as a member clock (Optional.) Configuring the role of a PTP port (Optional.) Configuring the port type for a TC+OC (Optional.) Setting the interval for sending announce messages and the interval timeout (Optional.) Setting the interval for sending Pdelay_Req messages (Optional.) Setting the interval for sending Sync messages (Optional.) Setting the delay correction value (Optional.) Setting the cumulative offset between the UTC and TAI (Optional.) Setting the correction date of the UTC (Optional.) Configuring a priority for a clock (Optional.) Specifying a VLAN tag for PTP messages (Optional.) Specifying the system time protocol as PTP (Required.) Enabling PTP on a port

Tasks at a glance

(Required.) Configuring PTP

Specifying a PTP standard

The PTP standard is IEEE 1588 version 2:

(Required.) Specifying a clock node type

(Optional.) Specifying a PTP domain

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

(Optional.) Configuring the role of a PTP port

(Optional.) Specifying a delay measurement mechanism for a BC or an OC

(Optional.) Configuring the port type for a TC+OC

(Optional.) Setting the interval for sending announce messages and the interval timeout

(Optional.) Setting the interval for sending Pdelay_Req messages

(Optional.) Setting the interval for sending Sync messages

(Optional.) Setting the minimum interval for sending Delay_Req messages

(Optional.) Configuring the MAC address for non-pdelay messages

(Optional.) Specifying the IPv4 UDP transport protocol for PTP messages

(Optional.) Configuring the source IP address for multicast PTP message transmission over

(Optional.) Configuring the destination IP address for unicast PTP message transmission over

(Optional.) Setting the delay correction value

(Optional.) Setting the cumulative offset between the UTC and TAI

(Optional.) Setting the correction date of the UTC

(Optional.) Configuring a priority for a clock

(Optional.) Setting a DSCP value for PTP messages transmitted over

(Optional.) Specifying a VLAN tag for PTP messages

(Optional.) Specifying the system time protocol as PTP

(Required.) Enabling PTP on a port

The PTP standard is IEEE 802.1AS (802.1AS):

(Required.) Specifying a clock node type

(Optional.) Specifying a PTP domain

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

(Optional.) Configuring the role of a PTP port

(Optional.) Configuring the port type for a TC+OC

(Optional.) Setting the interval for sending announce messages and the interval timeout

(Optional.) Setting the interval for sending Pdelay_Req messages

(Optional.) Setting the interval for sending Sync messages

(Optional.) Setting the delay correction value

(Optional.) Setting the cumulative offset between the UTC and TAI

(Optional.) Setting the correction date of the UTC

(Optional.) Configuring a priority for a clock

(Optional.) Specifying a VLAN tag for PTP messages

(Optional.) Specifying the system time protocol as PTP

(Required.) Enabling PTP on a port

Configuring PTP

Specifying a PTP standard

For PTP to operate correctly, specify a PTP standard before you configure PTP. Changing the PTP standard for the device clears all PTP configurations defined by the standard.

To specify a PTP standard:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Specify a PTP standard.	ptp profile { 1588v2 \| 8021as }	By default, no PTP standard is configured, and PTP is not running on the device.

Specifying a clock node type

You can configure only one of the following types of clock nodes for a device: OC, BC, E2ETC, P2PTC, E2ETC+OC, or P2PTC+OC.

Follow these guidelines when you specify a clock node type:

· Before you specify the clock node type, specify a PTP standard.

· If the PTP standard is IEEE 802.1AS, the clock node type cannot be E2ETC or E2ETC+OC.

· Changing the clock node type clears all PTP configurations except the PTP standard.

To specify a clock node type:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
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.

Specifying a PTP domain

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

To specify a PTP domain:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Specify a PTP domain for the device.	ptp domain value	By default, PTP devices are in PTP domain 0.

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.

This task is applicable only to OCs.

This configuration is automatically cleared after you change the clock node type for the device.

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

To configure an OC to operate only as a member clock:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure the OC to operate only as a member clock.	ptp slave-only	By default, the OC is not configured to operate only as a member clock.

Configuring a priority for a clock

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

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure the priority for the specified clock for GM election through BMC.	ptp priority clock-source local { priority1 priority1 \| priority2 priority2 }	If the PTP profile is IEEE 1588 version 2, the default value is 128 for both priority 1 and priority 2. If the PTP profile is IEEE 802.1AS, the default value is 246 for priority 1 and 248 for priority 2.

Step

Command

Remarks

1. Enter system view.

system-view

N/A

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

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

If the PTP profile is IEEE 1588 version 2, the default value is 128 for both priority 1 and priority 2.

If the PTP profile is IEEE 802.1AS, the default value is 246 for priority 1 and 248 for priority 2.

Configuring the role of a PTP port

Follow these guidelines when you configure the role of a PTP port:

· Only one subordinate port is allowed to be configured for a device.

· This task is also applicable to an OC that operates in slave-only mode.

· By default, the PTP port roles are automatically negotiated based on the BMC algorithm. If you use the ptp force-state command to change the role of one PTP port, all the other PTP ports in the PTP domain stop working. For these PTP ports to function, you must specify roles for each of them by using the ptp force-state command. As a best practice, enable automatic negotiation of PTP port roles based on the BMC algorithm.

To configure the PTP port role on an OC, BC, E2ETC+OC, or P2PTC+OC:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Configure the role of the PTP port.	ptp force-state { master \| passive \| slave }	By default, the PTP port role is automatically specified through BMC.
4. Quit interface view.	quit	N/A
5. Activate the port role configuration.	ptp active force-state	By default, the port role configuration is not activated.

Specifying a delay measurement mechanism for a BC or an OC

PTP defines two transmission delay measurement mechanisms: Request_Response and Peer Delay. Ports on the same link must share the same delay measurement mechanism. Otherwise, they cannot communicate with one another.

BCs and OCs do not have a default delay measurement mechanism. You must specify a delay measurement mechanism for them.

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

This task is applicable only to BCs and OCs.

If the PTP standard is IEEE 802.1AS, only Peer Delay mode is supported.

To specify a delay measurement mechanism for a BC or an OC:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Specify a delay measurement mechanism for a BC or an OC.	ptp delay-mechanism { e2e \| p2p }	By default, the delay measurement mechanism might vary depending on the PTP standard.

Configuring the port type for a TC+OC

All ports on a TC+OC (E2ETC+OC or P2PTC+OC) are TCs by default. This feature allows you to configure one of the ports as an OC. This task is applicable only to E2ETC+OCs and P2PTC+OCs.

When a TC+OC is synchronizing time to a downstream clock node through a TC, do not enable an OC to synchronize with the downstream clock node. Otherwise, time synchronization might be affected.

To configure the port type for a TC+OC as OC:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Configure the port type for a TC+OC as OC.	ptp port-mode oc	By default, the port type for all ports on a TC+OC is TC.

Setting the interval for sending announce messages and the interval timeout

A master node sends announce messages to the member nodes at the specified interval. If a member node does not receive any announce messages from the master node within the specified interval, it determines that the master node is invalid. The timeout = timeout multiplier × interval at which the master node sends announce messages.

To set the announce message sending interval and the interval timeout:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Set the interval for sending announce messages.	ptp announce-interval interval	By default: · The interval is 2 (21) seconds if the PTP standard is IEEE 1588 version 2. · The interval is 1 (20) second if the PTP standard is IEEE 802.1AS.
4. Set the number of intervals before a timeout occurs.	ptp announce-timeout multiple-value	By default, a timeout occurs when three intervals are reached.

For IEEE 1588 version 2, the timeout for receiving announce messages is the announce message sending interval for the subordinate node × multiple-value. For IEEE 802.1AS, the timeout for receiving announce messages is the announce message sending interval for the master node × multiple-value.

Setting the interval for sending Pdelay_Req messages

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. (Optional.) Set the interval for sending Pdelay_Req messages.	ptp pdelay-req-interval interval	The default is 1 (20) second.

Setting the interval for sending Sync messages

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Set the interval for sending Sync messages.	ptp syn-interval interval	By default: · The interval is 1 (20) second if the PTP standard is IEEE 1588 version 2. · The interval is 1/8 (2-3) seconds if the PTP standard is IEEE 802.1AS.

Setting the minimum interval for sending Delay_Req messages

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Set the minimum interval for sending Delay_Req messages.	ptp min-delayreq-interval interval	The default is 1 (20) second. When receiving a Sync or Follow_Up message, an interface can send Delay_Req messages only when the minimum interval is reached.

Configuring 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.

To configure the destination MAC address for non-Pdelay messages on every clock node:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Configure the destination MAC address for non-Pdelay messages.	ptp destination-mac mac-address	The default is 011B-1900-0000. This command takes effect only if PTP messages are encapsulated in IEEE 802.3/Ethernet packets.

Specifying the IPv4 UDP transport protocol for PTP messages

PTP messages can be transported over IEEE 802.3/Ethernet or IPv4 UDP.

To configure the IPv4 UDP transport protocol for PTP messages:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Configure the IPv4 UDP transport protocol for PTP messages.	ptp transport-protocol udp	By default, PTP messages are transported over IEEE 802.3/Ethernet.

Configuring the source IP address for multicast PTP message transmission over IPv4 UDP

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure the source IP address for multicast PTP message transmission over IPv4 UDP.	ptp source ip-address [ vpn-instance vpn-instance-name ]	By default, no source IP address is configured for multicast PTP messages. This command takes effect only when multicast PTP messages are transmitted over IPv4 UDP. The ptp unicast-destination command has precedence over the ptp source command.

Step

Command

Remarks

1. Enter system view.

system-view

N/A

2. Configure the source IP address for multicast PTP message transmission over IPv4 UDP.

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

By default, no source IP address is configured for multicast PTP messages.

This command takes effect only when multicast PTP messages are transmitted over IPv4 UDP.

The ptp unicast-destination command has precedence over the ptp source command.

Configuring the destination IP address for unicast PTP message transmission over IPv4 UDP

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Configure the destination IP address for unicast PTP message transmission over IPv4 UDP.	ptp unicast-destination ip-address	By default, no destination IP address is configured for unicast PTP message transmission. You must use this command on the current interface, and make sure the interface and the peer PTP interface can reach each other. This command takes effect only when unicast PTP messages are transmitted over IPv4 UDP. This command has precedence over the ptp source command.

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.

To set the delay correction value for every clock node:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. (Optional.) Set delay correction value.	ptp asymmetry-correction { minus \| plus } value	The default is 0 nanoseconds, which means delay correction is not performed.

Setting the cumulative offset between the UTC and TAI

The time displayed on a device is based on the Coordinated Universal Time (UTC). There is an offset between UTC and TAI (International Atomic Time, in English), which is made public periodically. This task allows you to adjust the offset between the UTC and TAI on the device. It is applicable only to the GM.

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

To set the cumulative offset between the UTC and TAI:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Set the cumulative offset between the UTC and TAI.	ptp utc offset utc-offset	The default is 0 seconds.

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.

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

To set the correction date of the UTC:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
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. If you execute this command multiple times, the most recent configuration takes effect. This command takes effect only on the GM.

Step

Command

Remarks

1. Enter system view.

system-view

N/A

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.

If you execute this command multiple times, the most recent configuration takes effect.

This command takes effect only on the GM.

Setting a DSCP value for PTP messages transmitted over IPv4 UDP

The DSCP value determines the sending precedence of a packet.

To set a DSCP value for PTP messages transmitted over IPv4 UDP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Set a DSCP value for PTP messages transmitted over IPv4 UDP.	ptp dscp dscp	By default, the DSCP value is 56.

Specifying a VLAN tag for PTP messages

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view.	interface interface-type interface-number	N/A
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.

Specifying the system time protocol as PTP

Make sure you use the clock protocol command to specify the time protocol as PTP. For more information about the clock protocol command, see Fundamentals Command Reference.

To specify the system time protocol as PTP:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Specify the system time protocol as PTP.	clock protocol ptp	By default, the device uses NTP to obtain time.

Enabling PTP on a port

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

To enable PTP on a Layer 2 Ethernet interface, make sure the VLAN interface for the VLAN to which the Layer 2 interface belongs is not associated with any VPN instance (the ip binding command not configured on the VLAN interface).

To enable PTP on a port:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter Layer 2 Ethernet interface view or Layer 3 Ethernet interface view.	interface interface-type interface-number	N/A
3. Enable PTP on the port.	ptp enable	By default, PPP is disabled on a port.

Displaying and maintaining 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 ]

PTP configuration examples

PTP configuration example (IEEE 1588 version 2, IEEE 802.3/Ethernet encapsulation, multicast transmission)

Network requirements

As shown in Figure 4, configure PTP (IEEE 1588 version 2, IEEE 802.3/Ethernet transport, multicast transmission) to enable time synchronization between the devices.

· Specify the IEEE 1588 version 2 PTP profile and the IEEE 802.3/Ethernet transport protocol for PTP messages on Device A, Device B, and Device C.

· Assign Device A, Device B, and Device C to the same PTP domain. 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 in the PTP domain.

· Use the default Request_Response delay measurement mechanism on Device A and Device C.

Figure 4 Network diagram

‌

Configuration procedure

1. Configure Device A:

# Specify the PTP standard as IEEE 1588 version 2.

<DeviceA> system-view

[DeviceA] ptp profile 1588v2

# Specify the clock node type as OC.

[DeviceA] ptp mode oc

# 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 PTP standard as IEEE 1588 version 2.

<DeviceB> system-view

[DeviceB] ptp profile 1588v2

# Specify the clock node type as E2ETC.

[DeviceB] ptp mode e2etc

# 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 PTP standard as IEEE 1588 version 2.

<DeviceC> system-view

[DeviceC] ptp profile 1588v2

# Specify the clock node type as OC.

[DeviceC] ptp mode oc

# 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

4. Verify 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

PTP configuration example (IEEE 1588 version 2, IPv4 UDP transport, multicast transmission)

Network requirements

As shown in Figure 5, configure PTP (IEEE 1588 version 2, IPv4 UDP transport, multicast transmission) to enable time synchronization between the devices.

· Specify the IEEE 1588 version 2 PTP profile for Device A, Device B, and Device C.

· Specify multicast IPv4 UDP transport for PTP messages.

· Assign Device A, Device B, and Device C to the same PTP domain. Specify the OC clock node type for Device A and Device C, and P2PTC clock node type for Device B. All clock nodes elect a GM through BMC in the PTP domain.

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

Figure 5 Network diagram

‌

Configuration procedure

1. Configure Device A:

# Specify the PTP standard as IEEE 1588 version 2.

<DeviceA> system-view

[DeviceA] ptp profile 1588v2

# Specify the clock node type as OC.

[DeviceA] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over IPv4 UDP.

[DeviceA] ptp source 11.10.10.1

# On Ten-GigabitEthernet 1/0/1, specify the IPv4 UDP transport protocol for PTP messages, specify the peer delay measurement mechanism, 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 PTP standard as IEEE 1588 version 2.

<DeviceB> system-view

[DeviceB] ptp profile 1588v2

# Specify the clock node type as P2PTC.

[DeviceB] ptp mode p2ptc

# Configure the source IP address for multicast PTP message transmission over IPv4 UDP.

[DeviceB] ptp source 10.10.10.2

# On Ten-GigabitEthernet 1/0/1, specify the IPv4 UDP transport protocol for PTP messages 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 IPv4 UDP transport protocol for PTP messages 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 PTP standard as IEEE 1588 version 2.

<DeviceC> system-view

[DeviceC] ptp profile 1588v2

# Specify the clock node type as OC.

[DeviceC] ptp mode oc

# Configure the source IP address for multicast PTP message transmission over IPv4 UDP.

[DeviceC] ptp source 10.10.10.3

# On Ten-GigabitEthernet 1/0/1, specify the IPv4 UDP transport protocol for PTP messages and the peer delay measurement mechanism, 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

4. Verify 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

PTP configuration example (IEEE 802.1AS, IEEE 802.3/Ethernet transport, multicast transmission)

Network requirements

As shown in Figure 6, configure PTP (IEEE 802.1AS, IEEE 802.3/Ethernet transport, multicast transmission) to enable time synchronization between Device A, Device B, and Device C.

· Specify the IEEE 802.1AS PTP profile for Device A, Device B, and Device C.

· Assign Device A, Device B, and Device C to the same PTP domain. Specify the OC clock node type for Device A and Device C, and P2PTC clock node type for Device B. The clock nodes elect a GM through BMC in the PTP domain.

· Use the peer delay measurement mechanism on all clock nodes in the PTP domain.

Figure 6 Network diagram

‌

Configuration procedure

1. Configure Device A:

# Specify the PTP standard as IEEE 802.1AS.

<DeviceA> system-view

[DeviceA] ptp profile 802.1AS

# Specify the clock node type as OC.

[DeviceA] ptp mode oc

# 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 PTP standard as IEEE 802.1AS.

<DeviceB> system-view

[DeviceB] ptp profile 802.1AS

# Specify the clock node type as P2PTC.

[DeviceB] ptp mode p2ptc

# 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 PTP standard as IEEE 1588 802.1AS.

<DeviceC> system-view

[DeviceC] ptp profile 802.1AS

# Specify the clock node type as OC.

[DeviceC] ptp mode oc

# 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

4. Verify 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 802.1AS

PTP mode : OC

Slave only : No

Clock ID : 000FE2-FFFE-FF0000

Clock type : Local

Clock domain : 0

Number of PTP ports : 1

Priority1 : 246

Priority2 : 248

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 16640

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 802.1AS

PTP mode : P2PTC

Slave only : No

Clock ID : 000FE2-FFFE-FF0001

Clock type : Local

Clock domain : 0

Number of PTP ports : 2

Priority1 : 246

Priority2 : 248

Clock quality :

Class : 248

Accuracy : 254

Offset (log variance) : 16640

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

11-Network Management and Monitoring Configuration Guide

Basic concepts

PTP profile

PTP domain

Clock node and PTP port

Master-member/subordinate relationship

Grandmaster clock

Local clock

Request_Response

Peer Delay

Specifying a PTP domain

Configuring an OC to operate only as a member clock

Setting the interval for sending announce messages and the interval timeout

Configuring the source IP address for multicast PTP message transmission over IPv4 UDP

Configuring the destination IP address for unicast PTP message transmission over IPv4 UDP

Setting a DSCP value for PTP messages transmitted over IPv4 UDP

Specifying the system time protocol as PTP

PTP configuration example (IEEE 1588 version 2, IEEE 802.3/Ethernet encapsulation, multicast transmission)

Network requirements

Configuration procedure

Network requirements

Configuration procedure

PTP configuration example (IEEE 802.1AS, IEEE 802.3/Ethernet transport, multicast transmission)

Network requirements

Configuration procedure

Cloud & AI

InterConnect

Intelligent Terminal Products

Product Support Services

Technical Service Solutions

Resource Center

Policy

Online Help

Become a Partner

Partner Resources

Partner Business Management

Company Information

News & Events

Contact Us