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Configuring Precision Time Protocol

 

You can configure the master clock and the slave clock for Precision Time Protocol (PTP) to help synchronize clocks in a distributed system. This time synchronization is achieved through packets that are transmitted and received in a session between the master clock and the slave clock.

Configuring PTP Options

To configure PTP options:

  1. In configuration mode, go to the [edit protocols ptp] hierarchy level:
  2. Configure the clock mode as either boundary or ordinary. This attribute is mandatory and has no default value.

    The boundary option signifies that the clock can be both a master clock and a slave clock. The ordinary option signifies that the clock is either a master clock or a slave clock.

  3. Configure the PTP domain option with values from 0 through 127. The default value is 0.
  4. Configure the priority1 option with values from 0 through 254. The default value is 128.

    The priority1 value determines the best master clock. The priority1-value is also advertised in the master clock’s announce message to other slaves.

  5. Configure the priority2 option with values from 0 through 255. The default value is 128.

    The priority2 value differentiates and prioritizes the master clock to avoid confusion when priority1-value is the same for different master clocks in a network.

  6. Configure the unicast-negotiation option to enable unicast negotiation.

    Unicast negotiation is a method by which the announce, sync, and delay response packet rates are negotiated between the master clock and the slave clock before a PTP session is established.

    Note

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

Configuring Slave Clock Options

Configure the following options after the aforementioned PTP options have been set.

  1. Configure the slave clock.
  2. Configure the announce-timeout option in the slave node with values from 2 through 10. The default value is 3.

    The announce timeout value signifies the number of times an announce interval message has to pass through the slave without receiving the announce message—that is, the timeout period for announce messages.

  3. Configure the delay-request option in the slave node with values from –6 through 6. The default value is –4.

    The delay request value is the logarithmic mean interval in seconds between the delay request messages sent by the slave to the master.

  4. Configure the frequency-only option to enable only frequency synchronization in the slave.
    Note

    This option is configured only when PTP is used for frequency synchronization and not for phase synchronization. Also, note that this option can only be set for an ordinary clock acting as slave.

  5. Configure the interface for the slave.
  6. Configure the unicast-mode option for the slave. You can set this option when PTP unicast mode of messaging is needed.
  7. Configure the transport option in unicast mode as IPv4.

    The encapsulation type for PTP packet transport is IPv4.

  8. Configure the IP address of the slave.
  9. Configure the IP address of the interface acting as the local PTP slave port.
    Note

    You must configure this IP address at the [edit interfaces interface-name] hierarchy level.

  10. You can configure PTP over IPv4 over a link aggregation group for MPC2E NG, MPC3E NG, MPC5E, MPC6E, MPC7E-10G, MPC7E-MRATE, MPC8E, and MPC9E.

    For each aggregated Ethernet link configured as PTP slave, you can specify one member link of the aggregated Ethernet bundle as primary and another as secondary.

  11. Starting in Junos OS Release 15.2R1, you can configure multicast mode option for the slave port. In this mode, PTP over Ethernet uses multicast addresses and a slave port can automatically start receiving the multicast announce messages transmitted by the master ports on a network. The slave port can start communicating with the master port with minimal or no configuration.
  12. Configure Ethernet as the encapsulation type of transport for the PTP packets. You can further enable 802.3 Ethernet encapsulation to use a specific set of multicast MAC addresses while transmitting the PTP packets over Ethernet.
    Note

    It is mandatory to use the transport statement while configuring the multicast-mode for master and slave interfaces.

  13. You can configure PTP over Ethernet over a link aggregation group for MPC5E, MPC6E, MPC7E-10G, MPC7E-MRATE, MPC8E, and MPC9E line cards.

    For each aggregated Ethernet link configured as PTP slave, you can specify one member link of the aggregated Ethernet bundle as primary and another as secondary.

Configuring Master Clock Options

Configure the following options after the aforementioned PTP options and slave clock options have been set.

  1. Configure the master clock.
  2. Configure the announce interval option for the master with values from 0 through 4. The default value is 1.

    The announce interval is the logarithmic mean interval between announce messages that is sent by the master. By default, one announce message is sent in every two seconds.

  3. Configure the clock step option as either one-step or two-step for the master. The default value is one-step.

    The clock step determines whether the timing information is sent along with the sync message only (one-step) or a subsequent follow-up message (two-step) is sent corresponding to the previous sync message.

  4. Configure the sync interval option for the master clock with values from –6 through 6. The default value is –6.

    The sync interval is the logarithmic mean interval between synchronous messages that is sent by the master. By default, 64 synchronous interval messages are sent per second.

  5. Configure the interface for the master.
  6. Configure the unicast mode option for the master. You can set this option when PTP unicast mode of messaging is needed.
  7. Configure the transport option in unicast mode as IPv4.

    The encapsulation type for PTP packet transport is IPv4.

  8. Configure the IP address for the slave.
  9. Configure the IP address of the interface acting as the local PTP master port.
  10. You can configure PTP over IPv4 over a link aggregation group for MPC2E NG, MPC3E NG, MPC5E, MPC6E, MPC7E-10G, MPC7E-MRATE, MPC8E, and MPC9E.

    For each aggregated Ethernet link configured as PTP master, you can specify one member link of the aggregated Ethernet bundle as primary and another as secondary.

  11. Starting with Junos OS Release 15.2R1, you can configure multicast mode option for the master port. In this mode, PTP over Ethernet uses multicast addresses and a slave port can automatically start receiving the multicast announce messages transmitted by the master ports on a network. The slave port can start communicating with the master port with minimal or no configuration.
  12. Configure Ethernet as the encapsulation type of transport for the PTP packets. You can further enable 802.3 Ethernet encapsulation to use a specific set of multicast MAC addresses while transmitting the PTP packets over Ethernet.
    Note

    It is mandatory to use the transport statement while configuring the multicast-mode for master and slave interfaces.

  13. You can configure PTP over Ethernet over a link aggregation group for MPC5E, MPC6E, MPC7E-10G, MPC7E-MRATE, MPC8E, and MPC9E line cards.

    For each aggregated Ethernet link configured as PTP master, you can specify one member link of the aggregated Ethernet bundle as primary and another as secondary.

Release History Table
Release
Description
Starting in Junos OS Release 15.2R1, you can configure multicast mode option for the slave port.
Starting with Junos OS Release 15.2R1, you can configure multicast mode option for the master port.