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PTP Clocks

SUMMARY The IEEE 1588v2 standard defines Precision Time Protocol (PTP), which is used to synchronize with accuracy the real-time clocks of the devices in a network. The clocks are organized in a hierarchical primary/client architecture for the distribution of time-of-day.

Configure PTP Clocking

In a distributed network, you can configure Precision Time Protocol (PTP) primary and client clocks to help synchronize the timing across the network. The synchronization is achieved through packets that are transmitted and received in a session between the primary clock and the client clock or clock client.

To configure Precision Time Protocol (PTP) options:

  1. In configuration mode, go to the [edit protocols ptp] hierarchy level.
  2. Specify the clock as a boundary or ordinary clock. The boundary option signifies that the clock can be both a primary clock and a client clock. The ordinary option signifies that the clock is a client clock.
  3. (Optional) Enable PHY Timestamping. The PHY timestamping is disabled by default.
  4. (Optional) Configure the PTP domain with values from 0 through 127. The default value is 0.
  5. (Optional) Specify the DiffServ code point (DSCP) value (0 through 63) for all PTP IPv4 packets originated by the router. The default value is 56.
  6. Specify the primary clock parameters.

    For details about configuring the primary clock parameters, see Configure PTP Primary Boundary Clock Parameters.

  7. (Optional) Configure the priority value of the clock (0 through 255). This value is used in selecting the best primary clock. The priority1-value is advertised in the primary clock’s announce message to clock clients. The default value is 128.

  8. (Optional) Configure the tie-breaker in selecting the best primary clock (0 through 255). The priority2 value differentiates and prioritizes the primary clock to avoid confusion when the priority1-value is the same for different primary clocks in a network. The default value is 128.
  9. Specify the PTP client clock parameters.

    For information about configuring the client clock options, see Configure PTP Primary Boundary Clock Parameters

  10. (Optional) Enable unicast negotiation. Unicast negotiation is a method by which the announce, synchronization, and delay response packet rates are negotiated between the primary clock and the clock client before a PTP session is established.
    Note:

    Unicast negotiation, when enabled, does not allow you to commit packet rate–related configurations.

PTP Boundary Clock Overview

An IEEE 1588v2 boundary clock has multiple network connections and can act as a source (primary) and a destination (client) for synchronization messages. It synchronizes itself to a best primary clock through a client port and supports synchronization of remote clock clients to it on primary ports.

PTP Boundary Clock

Boundary clocks can improve the accuracy of clock synchronization by reducing the number of 1588v2-unaware hops between the primary and the client. Boundary clocks can also be deployed to deliver better scale because they reduce the number of sessions and the number of packets per second on the primary.

The boundary clock intercepts and processes all PTP messages and passes all other traffic. The best primary clock algorithm (BMCA) is used by the boundary clock to select the best configured acceptable primary clock that a boundary client port can see. To configure a boundary clock, include the boundary statement at the [edit protocols ptp clock-mode] hierarchy level and at least one primary with the master statement and at least one client with the slave statement at the [edit protocols ptp] hierarchy level.

ACX5448 router supports PTP boundary clocks for phase and time synchronization using IEEE-1588 Precision Timing Protocol (PTP). The ACX5448 router supports the following features:

  • PTP over IPv4 (IEEE-1588v2)

  • PTP ordinary and boundary clocks

  • One step clock mode operation for PTP Primary

  • 10Mhz and 1PPS output for measurement purpose

All PTP packets uses the best-effort queue instead of network control queue.

If clksyncd-service restart is initiated, then the show ptp lock status detail CLI command output of Clock reference state and 1pps reference state fields shows incorrect information. The following is a sample of output for show ptp lock status detail:

Figure 1 illustrates two boundary clocks in a network in which the clock flow is from the upstream node (BC-1) to the downstream node (BC-2). This figure also applies to MX Series routers and QFX Series switches.

Figure 1: Boundary Clocks in a Network Boundary Clocks in a Network

The first boundary clock—BC-1—has four ports. Each port is configured as follows:

  • BC-1 P-1 and BC-1 P-4 are boundary client ports connected to two reference clocks—OC-1 and OC-5. The reference clocks are included as the clock sources in the client port configurations. From the packets received on the client ports, BC-1 selects the best primary, synchronizes its clock, and generates PTP packets, which are sent over the primary ports—BC-1 P-2 and BC-1 P-3—to the downstream clients.

  • BC-1 P-2, a primary port, is connected to OC-2, an ordinary remote client. OC-2 is included as a clock client in BC-1 P-2’s primary configuration, and so receives PTP packets from BC-1 P-2.

  • BC-1 P-3, a primary port, is connected to BC-2 P-1, a remote boundary client port. In this situation, the primary port—BC-1 P-3—is included as a clock source in the configuration of the boundary client port—BC-2 P-1. In addition, the boundary client port—BC-2 P-1—is included as a clock client in the configuration of the primary port—BC-1 P-3. With this configuration, the boundary client—BC-2 P1—receives PTP packets from BC-1 P3.

The second boundary clock—BC-2—has three ports. Each port is configured as follows:

  • BC-2 P-1 is a boundary client port connected to the upstream primary port—BC-1 P3. As described previously, BC-2 P-1 receives PTP packets from BC-1 P3. The primary ports—BC-2 P-2 and BC-2 P-3—synchronize their time from the packets received from BC-2 P1.

  • BC-2 P-2 and BC-2 P-3, boundary primary ports, are connected to ordinary remote slaves—OC-3 and OC-4. OC-3 and OC-4 are included as clock clients in the configuration of the primary ports—BC-2 P2 and BC-2 P-3. Both slaves receive PTP packets from the primary boundary port to which they are connected.

In this example, the boundary clock synchronizes its clock from the packets received on its client ports from the upstream primary. The boundary clock then generates PTP packets, which are sent over the primary port to downstream clients. These packets are timestamped by the boundary clock by using its own time, which is synchronized to the selected upstream primary.

Clock Clients

A clock client is the remote PTP host, which receives time from the PTP primary and is in a client relationship to the primary.

Note:

The term client is sometimes used to refer to the clock client.

An device acting as a primary boundary clock supports the following types of downstream clients:

  • Automatic client—An automatic client is configured with an IP address, which includes the subnet mask, indicating that any remote PTP host belonging to that subnet can join the primary clock through a unicast negotiation. To configure an automatic client, include the subnet mask in the clock-client ip-address statement at the [edit protocols ptp master interface interface-name unicast-mode] hierarchy level.

  • Manual client—A manual client is configured with the manual statement at the [edit protocols ptp master interface interface-name unicast-mode clock-client ip-address local-ip-address local-ip-address] hierarchy level. A manual client does not use unicast negotiation to join the primary clock. The manual statement overrides the unicast negotiation statement configured at the [edit protocols ptp] hierarchy level. As soon as you configure a manual client, it starts receiving announce and synchronization packets.

  • Secure client—A secure client is configured with an exact IP address of the remote PTP host, after which it joins a primary clock through unicast negotiation. To configure a secure client, include the exact IP address in the clock-client ip-address statement at the [edit protocols ptp master interface interface-name unicast-mode] hierarchy level.

Note:

You can configure the maximum number of clients (512 ) in the following combination:

  • Automatic clients 256.

  • Manual and secure clients 256—Any combination of manual and secure clients is allowed as long as the combined total amounts to 256.

PTP Boundary Clock Over IRB for Broadcast Profiles

The IEEE 1588 PTP boundary clock (BC) applications for broadcast media often requires many PTP streams to use a common local IP address. These packets are forwarded through L2 switching. In these use cases, there are no physical interface IFLs created for each PTP physical interface, as would be usually expected for PTP configurations on physical interfaces. Configuration over integrated routing and bridging (IRB) interfaces allows you to meet this requirement. Currently, there is an existing feature that supports multicast-mode with physical interfaces. PTP over IRB for broadcast profiles will extend this support for physical interfaces on IRB interfaces. PTP BC over IRB for broadcast profiles will support SMPTE/AES67/AES67-SMPTE profiles (multicast PTP over IP). This new interface type is added to the multicast profiles. The PTP multicast-mode supports IRB interfaces using the IPv4 transport type that is used with physical interfaces.

Note:

PTP BC features developed for QFX5110 and QFX5200 are still available. Support is extended to IRB interfaces for PTP BC over multicast for broadcast profiles.

CLI Configuration

A new CLI configuration is added to this feature for multicast mode to identify the L2 interface that needs to be transported. This new interface type is supported in the example configuration statements below.

IPv4 Configuration Example

Multiple IRB IPv4 Configuration Example

CLI Commands

There are no new operational commands being added. Areas in the display output that show an interface name will show the appropriate name for the IRB interface and will be expanded to include the L2 IFL name for IRB interfaces.

Note:

Available vty commands that are used to help diagnose the operation of the clksyncd and PTP protocol stack will not change, but will support the new interface types and information.

show ptp lock-status detail

show ptp primary detail

show ptp slave detail

show ptp statistics

show ptp statistics detail

Configure PTP Primary Boundary Clock

A Precision Time Protocol (PTP) primary boundary clock sends PTP messages to the clients (ordinary and boundary) so that they can establish their relative time offset from this primary’s clock or clock reference. You cannot configure an ordinary primary clock on a device. The primary boundary clock synchronizes time through a boundary client port. To configure a primary boundary clock, you must include the boundary statement at the [edit protocols ptp clock-mode] hierarchy level and at least one primary with the master statement and at least one client with the slave statement at the [edit protocols ptp] hierarchy level. ACX5048 and ACX5096 routers do not support ordinary and boundary clock.

To configure a PTP primary boundary clock, complete the following tasks:

Configure PTP Primary Boundary Clock Parameters

To configure the parameters of a PTP primary boundary clock:

  1. Configure the clock mode.
  2. Configure the primary clock.
  3. (Optional) Specify the log mean interval between announce messages—from 0 through 4. By default, one announce message is sent every two seconds. This configuration is used for manual clock clients. The primary boundary clock sends announce messages to manual clock clients as specified in the announce-interval value.
  4. Configure the interface on which to respond to downstream PTP clients and slaves.
  5. (Optional) Specify the maximum log mean interval between announce messages—from 0 through 4. The default value is 4.
  6. (Optional) Specify the maximum log mean interval between delay-response messages—from –7 through 4. The default value is 4.
  7. (Optional) Specify the maximum log mean interval between synchronization messages—from –7 through 4. The default value is 4.
  8. (Optional) Specify the minimum log mean interval between announce messages—from –0 through 4. The default value is 0.
  9. (Optional) Specify the minimum log mean interval between delay-response messages—from –7 through 4. The default value is –7.
  10. (Optional) Specify the minimum log mean interval between synchronization messages—from –7 through 4. The default value is –7.
  11. (Optional) Specify the log mean interval between synchronization messages—from –7 through 4. The default value is –6. This configuration is used for manual clock clients. The primary boundary clock sends synchronization messages to manual clock clients as specified in the syn-interval-value statement.

After you have configured the PTP primary boundary clock parameters, enter the commit command from configuration mode. To complete the configuration of the primary boundary clock, complete Configure a PTP Primary Boundary Clock Interface.

Configure a PTP Primary Boundary Clock Interface

After you have configured the primary boundary clock parameters, complete the configuration of the primary boundary clock by configuring an interface to act in the role of the primary clock.

To configure a PTP primary boundary clock interface:

  1. Configure the interface on which to respond to downstream PTP slaves or clients.
    Note:

    For the configuration to work, the interface you specify must be configured at the [edit interfaces interface-name] hierarchy level.
  2. On this interface, configure downstream PTP clients.
  3. Configure the IP address of the remote PTP host, or configure a subnet mask so that any host belonging to that subnet can join the primary clock. You can configure up to 512 clients for each primary boundary clock.
    Note:

    You can configure the maximum number of clients (512 ) in the following combination:

    • Automatic clients 256.

    • Manual and secure clients 256—Any combination of manual and secure clients is allowed as long as the combined total amounts to 256.
    Note:

    When you toggle from a secure client to an automatic client or vice versa in the PTP configuration of a boundary clock, you need to delete the existing PTP configuration and issue the commit command, and then you add a new PTP configuration and issue the commit command.
  4. Configure the IP address of the interface acting as the local PTP primary.
  5. (Optional) When the unicast-negotiation statement is configured at the [edit protocols ptp] hierarchy level, configure a clock client to immediately receive announce and synchronization messages from the primary boundary clock without unicast negotiation.
  6. Specify the encapsulation type for PTP packet transport—IPv4. This statement is mandatory.

After you have configured the PTP primary clock interface, enter the commit command from configuration mode.

Example: Configure PTP Boundary Clock

This example shows how to configure a Precision Timing Protocol (PTP) boundary clock. A boundary clock must include the configuration of at least one primary and at least one client. The boundary primary receives time from a remote primary through the client, and in turn passes that time on to clock clients, which are in a client relationship to the boundary primary. In this example, you configure a primary, client, clock source, and clock client.

Note:

ACX5048 and ACX5096 routers do not support boundary clock.

Requirements

This example uses the following hardware and software components:

Note:

This example also applies to QFX Series switches. QFX Series switches do not support Gigabit Ethernet interfaces. Instead, configure PTP boundary clock parameters on 10-Gigabit Ethernet interfaces.

  • An ACX Series router

  • Junos OS Release 12.3 or later

Overview

In this example, the client clock or clock client immediately receives announce and synchronization packets after completion of the configuration.

Configuration

Procedure

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level:

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy.

To configure a boundary clock without unicast negotiation:

  1. Configure the clock mode.

  2. Configure the client interface.

  3. Configure the upstream unicast PTP primary clock source parameters.

  4. Configure the encapsulation type for PTP packet transport.

  5. Configure the IP address of the primary interface.

  6. Specify the IP address and subnet of the remote PTP host, and the IP address of the local PTP primary interface.

    Note:

    For the configuration to work, the primary interface you specify must be configured with this IP address at the [edit interfaces interface-name] hierarchy level.

  7. Configure the encapsulation type for PTP packet transport.

Results

From configuration mode, confirm your configuration by entering the show command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

After you have configured the device, enter the commit command from configuration mode.

Example: Configure PTP Boundary Clock With Unicast Negotiation

This example shows how to configure a boundary clock with unicast negotiation turned on and a mixture of manual, secure and automatic clock clients, which have a client relationship to the primary boundary clock. The unicast negotiation applies to clock sources, which are configured on the client or clock client. Clock clients, configured on the primary, are not affected by unicast negotiation.

Note:

ACX5048 and ACX5096 routers do not support boundary clock.

In this example, unicast-negotiation is applicable only to clock-sources. For clock clients, the statement unicast-negotiation at the [edit protocols ptp] hierarchy level is not effective.

Requirements

This example uses the following hardware and software components:

Note:

This example also applies to QFX Series switches. QFX Series switches do not support Gigabit Ethernet interfaces. Instead, configure PTP boundary clock parameters on 10-Gigabit Ethernet interfaces.

  • An ACX Series router

  • Junos OS Release 12.3 or later

Overview

A PTP client clock or clock client can join a primary clock with and without unicast negotiation. With unicast negotiation, the announce, synchronization, and delay response packet rates are negotiated between the primary and the client before a PTP session is established. Without unicast negotiation and after it is configured, the client or client immediately receives announce and synchronization packets.

A clock client is the remote PTP host, which receives time from the PTP primary. The following clock clients are configured in this example:

  • Secure client—A secure client is configured with an exact IP address, after which, it joins a primary clock through unicast negotiation. In this example, the clock client clock-client 117.117.117.117/32 local-ip-address 109.109.109.53 is a secure client, which means that only this specific host from the subnet can join the primary clock through a unicast negotiation .

  • Automatic client—An automatic client is configured with an IP address, which includes a subnet mask, indicating that any PTP host belonging to that subnet, can join the primary clock through a unicast negotiation. In this example, the clock client clock-client 109.109.109.0/24 local-ip-address 109.109.109.53 is an automatic client. Additionally, this automatic client is configured on the same primary clock interface—109.109.109.53—as the secure client.

  • Manual client—A manual client does not use unicast negotiation to join the primary clock. The manual statement overrides the unicast-negotiation statement configured at the [edit protocols ptp] hierarchy level. As soon as you configure a manual client, it starts receiving announce and synchronization packets. In this example, the clock client clock-client 7.7.7.7 local-ip-address 7.7.7.53 manual is the manual client and is configured on a second primary clock interface.

Configuration

A boundary clock must include the configuration of at least one primary and at least one client. The boundary primary receives time from a remote primary through the client, and in turn passes that time on to clock clients, which are in a client relationship to the boundary primary. In this example, you configure a boundary client, two Precision Time Protocol (PTP) boundary primaries with three different kinds of clock clients—automatic, manual, and secure. Two of the clock clients are configured on the same boundary primary.

Procedure

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level:

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure a boundary clock with unicast negotiation:

  1. Configure the clock mode.

  2. Enable unicast negotiation.

  3. Configure the local client interface from which the boundary primary receives time and passes it on to the configured clock clients.

  4. Configure the upstream unicast PTP primary clock source parameters.

  5. Configure the encapsulation type for PTP packet transport.

  6. Configure the PTP primary parameters by specifying the IP address of the PTP primary clock and the IP address of the local interface.

  7. Configure the first primary interface in this example.

  8. On the first primary interface, configure the downstream PTP clock clients.

  9. On the first primary interface, configure the encapsulation type for PTP packet transport.

  10. On the first primary interface, configure the PTP primary parameters by specifying the exact IP address of the remote PTP host and the IP address of the local PTP primary interface.

  11. On the first primary interface, configure a second PTP primary by specifying the IP address and subnet of the second remote PTP host and the IP address of the local PTP primary interface.

  12. Configure the second primary interface with the following parameters: the encapsulation type, the downstream PTP host, the IP address of the local PTP primary interface, and the manual statement so that this client does not use unicast negotiation.

Results

From configuration mode, confirm your configuration by entering the show command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

After you have configured the device, enter the commit command from configuration mode.

Configure PTP Member Clock

The client port that you configure can be a Precision Time Protocol (PTP) boundary or ordinary clock, depending on the configuration of the clock-mode statement at the [edit protocols ptp] hierarchy level. An ordinary or boundary client clock performs frequency and phase recovery based on received and requested timestamps from a primary clock—a reference or a boundary clock primary.

Note:

In ACX Series routers, the reference clock functionality is supported only on ACX500 router.

To configure a PTP member clock, complete the following tasks:

Configure the PTP Member Clock Parameters

To configure a PTP member clock parameters:

Note:

The clock-class-to-quality-level-mapping quality-level, convert-clock-class-to-quality-level, and grant-duration statements are not supported on the QFX10002 switch.
  1. Configure the clock mode:
  2. Configure the client clock.
  3. (Optional) Specify the rate of announce messages that a PTP client requests from the primary during a unicast-negotiation session—from 0 through 4. The default value is 1.
    Note:

    The configuration of the announce-interval statement is effective only when the unicast-negotiation statement is also configured at the [edit protocols ptp] hierarchy level.
  4. (Optional) Specify the number of announce messages that a client—configured on an ACX Series router—must miss before an announce timeout is declared—from 2 through 10. The default value is 3.
  5. (Optional) Override the default PTP clock class to Ethernet Synchronization Message Channel (ESMC) mapping and specify the quality level for the PTP timing source.
  6. (Optional) Enable retrieval of ESMC information from the PTP clock class.
  7. (Optional) Specify the logarithmic mean interval in seconds between the delay request messages sent by the client to the primary—from –6 through 3. The default value is 0.
  8. (Optional) Specify the grant duration value. When unicast negotiation is enabled, the local PTP client requests announce, synchronization, and delay-response messages from the primary. In each request, the client asks for the packets to be sent at a specified rate and the client provides a duration for which the rate is valid. The grant-duration value is specified in seconds. The default grant duration is 300 seconds.
  9. Configure the interface for the client.

    For details about configuring the member clock interface, see Configure the PTP Member Clock Interface.

  10. (Optional) Configure the log mean interval between synchronization messages—from –6 through -3. The default value is –6 or 64 synchronous interval messages sent per second

After you have configured the PTP client clock parameters, enter the commit command from configuration mode. To complete the configuration of the client clock, complete Configure the PTP Member Clock Interface.

Configure the PTP Member Clock Interface

The member clock interface responds to the upstream PTP primary clock.

To configure the PTP member clock interface:

  1. Configure the interface for the client clock.
    Note:

    On the QFX Series, you can configure an aggregated Ethernet interface and its configured IP address for PTP streams acting as slaves or primaries.

    For example, to configure a client using an aggregated Ethernet interface:

    Note:

    On the QFX Series, you can configure a loopback interface (there is only one loopback interface, and it is lo0.0) and its corresponding IP addresses for PTP streams acting as slaves or primaries. Although the loopback interface is the same for both primaries and slaves, the IP addresses must be unique.

    For example, to configure a client using the loopback interface:

  2. Configure the upstream unicast PTP primary clock source parameters.
  3. Configure the IP address of the primary, which acts as a source of time for this client.
    Note:

    To configure additional primary clock sources for the client, include the clock-source statement up to four times. However, synchronization is to only one primary clock.
  4. Specify the IP address of the interface acting as the local PTP client port.
    Note:

    For the configuration to work, the interface you specify must be configured with this IP address at the [edit interfaces interface-name] hierarchy level.
  5. Configure the encapsulation type for PTP packet transport. This statement is mandatory.

After you have configured the PTP member clock interface, enter the commit command from configuration mode.

Example: Configure Ordinary Member Clock With Unicast-Negotiation

This example shows the base configuration of a Precision Time Protocol (PTP) ordinary client clock with unicast-negotiation on an ACX Series router.

Note:

ACX5048 and ACX5096 routers do not support ordinary clock.

Requirements

This example uses the following hardware and software components:

Note:

This example also applies to QFX Series switches. QFX Series switches do not support Gigabit Ethernet interfaces. Instead, configure PTP boundary clock parameters on 10-Gigabit Ethernet interfaces.

  • One ACX Series router

  • Junos OS Release 12.2 or later

Overview

In this configuration, the ordinary client clock uses unicast-negotiation and compensates for some network asymmetry.

Note:

The values in this example are for illustration purposes only. You can set the values for each parameter according to your requirements.

Configuration

To configure an ordinary client clock with unicast-negotiation, perform these tasks:

CLI Quick Configuration

Configuring an ordinary client clock with unicast-negotiation

Step-by-Step Procedure

  1. Configure the clock mode, domain, and unicast-negotiation:

  2. Configure the announce timeout and the announce interval:

  3. Configure the synchronization interval and the grant duration:

  4. Configure the client interface:

  5. Configure the unicast transport mode:

  6. Configure the clock source:

  7. Configure the asymmetric path:

  8. Verify the configuration:

    See the output for the show command in the Results section.

Results

The following output shows the configuration of unicast-negotiation and compensation for some network asymmetry. The unicast-negotiation statement includes the parameters for the delay request, announce interval, synchronization interval, and grant duration values. Interface ge-0/1/0.0 is configured to compensate for an asymmetric path to the PTP master by subtracting 4.5 microseconds from the client-to-master direction delay calculations.

Example: Configure Ordinary Member Clock Without Unicast Negotiation

This example shows the base configuration of a Precision Time Protocol (PTP) ordinary client clock without unicast-negotiation on an ACX Series router.

Note:

ACX5048 and ACX5096 routers do not support ordinary clock.

Requirements

This example uses the following hardware and software components:

Note:

This example also applies to QFX Series switches. QFX Series switches do not support Gigabit Ethernet interfaces. Instead, configure PTP boundary clock parameters on 10-Gigabit Ethernet interfaces.

  • One ACX Series router

  • Junos OS Release 12.2 or later

Overview

In this configuration, unicast-negotiation is not configured, so the PTP client has no control over the rate of the negotiation. The PTP primary (a Brilliant Reference Clock or an MX Series router) must be configured with the parameters of the PTP client, such as announce, synchronization, and delay-response packets to control the rate of the negotiation.

Note:

The values in this example are for illustration purposes only. You can set the values for each parameter according to your requirements.

Configuration

To configure an ordinary client clock without unicast-negotiation, perform these tasks:

Note:

The ipv4-dscp statement is not supported on the QFX10002 switch.

CLI Quick Configuration

Configuring an ordinary client clock without unicast-negotiation

Step-by-Step Procedure

  1. Configure the clock mode:

  2. Configure the Differentiated Services code point (DSCP) value for all PTP IPv4 packets originated by the device:

    Note:

    The ipv4-dscp 46 statement is not supported on QFX Series switches.

  3. Configure the client interface:

  4. Configure the unicast transport mode:

  5. Configure the clock source:

  6. Verify the configuration:

    See the output for the show command in the Results section.

Results

In this example, the PTP client on the local interface ge-0/2/0 is assigned a local IP address of 12.1.1.5. Unicast-negotiation is not configured so the PTP master must be explicitly configured with the details of the PTP client (12.1.1.5).

PTP Transparent Clocks

The Precision Time Protocol (PTP) standardized by IEEE 1588 improves the current methods of synchronization used within a distributed network. You can use PTP across packet-based networks including, but not limited to, Ethernet networks. Queuing and buffering delays in the switch can cause variable delay to packets, which affects path delay measurements. Queuing delays vary based on the network load and also depend on the architecture of the switch or the router.

Transparent clocks measure and adjust for packet delay. The transparent clock computes the variable delay as the PTP packets pass through the switch or the router.

The QFX5100, EX4600, ACX5048, ACX5096, ACX6360-OR, and PTX10001-20C devices act as transparent clocks only and operate between the primary and client clocks in a distributed network. Transparent clocks improve synchronization between the primary and client clocks and ensure that the primary and client clocks are not impacted by the effects of packet delay variation. The transparent clock measures the residence time (the time that the packet spends passing through the switch or the router), and adds the residence time into the correction field of the PTP packet. The client clock accounts for the packet delay by using both the timestamp of when it started and the information in the correction field.

ACX5048 , ACX5096, ACX6360-OR, and PTX10001-20C devices support end-to-end transparent clocks. With an end-to-end transparent clock, only the residence time is included in the correction field of the PTP packets. The residence timestamps are sent in one packet as a one-step process. In a two-step process, which is not supported on ACX6360-OR, and PTX10001-20C devices, estimated timestamps are sent in one packet, and additional packets contain updated timestamps.

Note:

ACX5048 , ACX5096, ACX6360-OR, and PTX10001-20C devices support only the one-step process, which means that the timestamps are sent in one packet.

You can enable or disable a transparent clock globally for the switch or router. With a global configuration, the same configuration is applied to each interface. If the transparent clock is disabled, PTP packet correction fields are not updated. If the transparent clock is enabled, the PTP packet correction fields are updated.

On QFX5100, EX4600, and EX4400 switches, PTP over Ethernet, IPv4, IPv6, unicast, and multicast for transparent clocks are supported. EX4400 switches also support IRB and LAG. EX4300 and EX4300-MP switches do not support PTP transparent clock on virtual chassis mode.

Note:

ACX5048 and ACX5096 routers do not support PTP over IPv6 for transparent clocks.

Note:

ACX6360-OR, PTX10001-20C, and PTX10001-36MR devices support PTP over IPv6 for transparent clocks.

ACX5048 and ACX5096 routers do not support the following:

  • Boundary clock

  • Ordinary clock

  • Transparent clock over MPLS switched path

  • Transparent clock with more than two VLAN tags

ACX6360-OR and PTX10001-20C devices do not support the following:

  • Boundary, ordinary, primary, and client clocks

  • Transparent clock over MPLS switched path

  • Transparent clock with more than two VLAN tags

  • PTP over Ethernet

  • PTP over IPv4

  • PTP multicast mode

  • Configuration of unicast and broadcast modes.

    Unicast mode is enabled by default.

  • Transparent clock in transponder mode

  • PTP while MACSec is enabled

  • Two-step process

Note:

You might notice higher latency when you use copper SFP ports instead of fiber SFP ports. In this case, you must compensate the latency introduced by the copper SFP ports for the accurate CF (correction factor) measurement.

Configure PTP Transparent Clock

ACX Series routers supports transparent clock functionality. A Precision Time Protocol (PTP) Transparent clock measures the residence time of PTP packets as they pass through router. This residence time is added to the Correction Field of the PTP packet.

Note:

Starting in Junos OS Release 17.1 onwards, to configure transparent clock, include the e2e-transparent CLI command at the [edit protocols ptp] hierarchy level. Prior to Junos OS Release 17.1, to configure transparent clock, include the transparent-clock CLI command at the [edit protocols ptp] hierarchy level.

In a distributed network, you can configure transparent clock for Precision Time Protocol (PTP) for synchronizing the timing across the network. Junos OS supports the e2e-transparent CLI statement at the [edit protocols ptp] hierarchy level to configure transparent clock for Precision Time Protocol (PTP).

The following points need to be considered while configuring a PTP transparent clock in ACX routers:

  • Domain numbers—Transparent clock functionality would compute the residence time for PTP packets belonging to all domains.

  • PTP-over-MPLS—Transparent clock functionality do not support PTP carried over MPLS in ACX routers.

The PTP transparent clock functionality is supported on PTP-over-IP and PTP-over-Ethernet (PTPoE).

Note:

ACX routers do not support PTPoE over VLANs when it works in ordinary clock or boundary clock mode.
Note:

When the IGMP snooping-enabled routers and switches that are configured with PTP Transparent clock fail to perform the IGMP snooping, use the static IGMP configuration to forward the PTP traffic.

To configure a PTP transparent clock:

  1. Configure the clock mode:

  2. Configure the transparent clock: