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Configuring Clock Synchronization Interface on MX Series Routers

MX Series routers support external clock synchronization for Synchronous Ethernet, T1 or E1 line timing sources, and external inputs. Configuring external clock synchronization requires making clock selection, quality level, and priority considerations. The clock source selection algorithm is used to pick the two best upstream clock sources from among the various sources on the basis of system configuration and execution criteria such as quality level, priority, and hardware restrictions. For information about the clock synchronization options, see Understanding Clock Synchronization.

The following sections explain configuring clock synchronization options for MX Series routers:

Note:

Starting with Junos OS Release 13.3, the following scenarios occur when you configure Synchronous Ethernet without the clock-class-to-quality-level-mapping statement at the [edit protocols ptp slave] hierarchy level:

  • Qualified clock source quality level (that is the secondary clock source quality level) is transmitted out of the external interface and the Ethernet interface during clock reference switchover when two clock sources on different MICs of the same FPC exist or when two clock sources on two different FPCs exist.

  • Lower quality level is transmitted out the external interface and the Ethernet interface during clock reference switchover when two clock sources on the same MIC of an FPC exist due to hardware limitation.

Before you remove the SCBE from the router, you must delete the configuration under the [edit chassis synchronization] hierarchy level. Similarly, before you remove the SCBE2 from the router, you must delete the configuration under the [edit chassis synchronization] hierarchy level.

On SCBE2, the external-0/0 interface is located on SCB0 and the external-1/0 interface is located on SCB1.

Configuring Clock Synchronization Options

To configure the clock synchronization options.

  1. In configuration mode, go to the [edit chassis synchronization] hierarchy level.
  2. Configure the Synchronous Ethernet clock selection mode as auto-select or free-run.
  3. Configure the ESMC transmit parameters on all the interfaces or on selected interfaces.
  4. Configure the hold interval as configuration-change, which is the wait time (from 15 seconds through 60 seconds) after a change in configuration; restart, which is the wait time (from 60 seconds through 180 seconds) after reboot of the router; and switchover, which is the switchover wait time (from 30 seconds through 60 seconds) after clock recovery.
  5. Configure the options for the external interfaces on the basis of the type of Enhanced Switch Control Board on your MX Series router.

    The SCBE has only one external interface. Configure the following options for SCBE:

    1. Go to the [edit chassis synchronization interfaces external] hierarchy level.
    2. Configure all the E1 interface-specific options—the framing statement as g704 or g704-no-crc, the line-encoding statement as ami or hdb3, and the sabit statement from 4 bits through 8 bits.
    3. Configure the pulse-per-second-enable statement to enable the pulse per second (PPS) signal to be received on the GPS interface.
    4. Configure the frequency for the provided reference clock as 1 MHz, 5 MHz, 10 MHz, 2048 kHz, e1, or t1.
    5. Configure the T1 interface-specific options—the framing statement as esf or sf and the line-encoding statement as ami or b8zs.

    The SCBE2 Control Board has two external interfaces—external-0/0 and external-1/0. Configure the following options for SCBE2 Control Board:

    1. Go to the [edit chassis synchronization interfaces external-0/0] or [edit chassis synchronization interfaces external-1/0] hierarchy level.

      OR

    2. Configure all the E1 interface-specific options—the framing statement as g704 or g704-no-crc, the line-encoding statement as ami or hdb3, and the sabit statement from 4 bits through 8 bits-—on the external-0/0 interface or the external-1/0 interface.
    3. Configure the pulse-per-second-enable statement to enable the pulse per second (PPS) signal to be received on the GPS interface of the router.
    4. Configure the frequency for the provided reference clock as 1 MHz, 5 MHz, 10 MHz, 2048 kHz, e1, or t1.
    5. Configure the T1 interface-specific options—the framing statement as esf or sf and the line-encoding statement as ami or b8zs.

    The MX2020 Control Board has two external interfaces—external-a and external-b. Configure the following options for MX2020 Control Board:

    1. Go to the [edit chassis synchronization interfaces external-a] or [edit chassis synchronization interfaces external-b] hierarchy level.

      OR

    2. For BITS interface, configure all the E1 interface-specific options—the framing statement as g704 or g704-no-crc, the line-encoding statement as ami or hdb3, and the sabit statement from 4 bits through 8 bits-—on the external-a interface or the external-b interface.
    3. Configure the pulse-per-second-enable statement to enable the pulse per second (PPS) signal to be received on the GPS interface of the router.
    4. Configure the frequency for the provided reference clock as 1 MHz, 5 MHz, or 10 MHz for GPS interface and 2048 kHz, e1, or t1 for BITS interface.
    5. For BITS interface, configure the T1 interface-specific options—the framing statement as esf or sf and the line-encoding statement as ami or b8zs.
  6. Configure the maximum transmit quality level as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc.
  7. Configure the EEC synchronization networking type as option-1 or option-2.
  8. Configure the options for the external clock interface output on the basis of the type of Enhanced Switch Control Board on your MX Series router.

    For SCBE:

    1. Go to the [edit chassis synchronization output interfaces external] hierarchy level.
    2. Configure all the external clock interface output options. The options include the holdover-mode-disable statement; the minimum-quality statement, which can be set as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the source-mode statement, which can be set as chassis or line; the tx-dnu-to-line-source-enable statement; and the wander-filter-disable statement.

    For SCBE2:

    1. Go to the [edit chassis synchronization output interfaces external-0/0] hierarchy level or the [edit chassis synchronization output interfaces external-1/0] hierarchy level.
    2. Configure all the external clock interface output options on the external-0/0 interface or the external-1/0 interface. The options include the holdover-mode-disable statement; the minimum-quality statement, which can be set as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the source-mode option, which can be set as chassis or line; the tx-dnu-to-line-source-enable statement; and the wander-filter-disable statement.

    For MX2020 Control Board:

    1. Go to the [edit chassis synchronization output interfaces external-a] hierarchy level or the [edit chassis synchronization output interfaces external-b] hierarchy level.
    2. Configure all the external clock interface output options on the external-a interface or the external-b interface. The options include the holdover-mode-disable statement; the minimum-quality statement, which can be set as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the source-mode option, which can be set as chassis or line; the tx-dnu-to-line-source-enable statement; and the wander-filter-disable statement.
  9. Configure the time-of-day message format as ASCII on the auxiliary port that receives the external clock signals.
  10. Configure the quality-mode-enable statement to enable Synchronous Ethernet ESMC quality mode.
  11. Configure the selection mode for the incoming ESMC quality as configured-quality or received-quality.
  12. Configure the options for the ESMC source related external clock source interface on the basis of the type of Enhanced Switch Control Board on your MX Series router.

    For SCBE:

    1. Go to the [edit chassis synchronization source interfaces external] hierarchy level or the [edit chassis synchronization source interfaces ethernet-interface-name] hierarchy level.

      OR

    2. Configure the external clock interface and the Ethernet interface with their options. Configure the priority statement from 1 through 5; the quality-level statement as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the request statement as force-switch or lockout; the wait-to-restore statement from 0 minutes to 12 minutes; and the hold-off-time statement from 300 through 1800 milliseconds. You can configure the same options for the Ethernet interfaces as well.

    For SCBE2 Control Board:

    1. Go to the [edit chassis synchronization source interfaces (external-0/0] hierarchy level or the [edit chassis synchronization source interfaces (external-1/0] hierarchy level.

      OR

    2. Configure the options on the external-0/0 interface or the external-1/0 interface. Set the priority statement from 1 through 5; the quality-level statement as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the request statement as force-switch or lockout; the wait-to-restore statement from 0 minutes to 12 minutes; and the hold-off-time statement from 300 through 1800 milliseconds.

    For MX2020 Control Board:

    1. Go to the [edit chassis synchronization source interfaces (external-a] hierarchy level or the [edit chassis synchronization source interfaces (external-b] hierarchy level.

      OR

    2. Configure the options on the external-a interface or the external-b interface. Set the priority statement from 1 through 5; the quality-level statement as prc, prs, sec, ssu-a, ssu-b, st2, st3e, stu, or tnc; the request statement as force-switch or lockout; the wait-to-restore statement from 0 minutes to 12 minutes; and the hold-off-time statement from 300 through 1800 milliseconds.
  13. Configure the switchover mode as revertive or non-revertive.

Display the External Clock Synchronization Configuration for SCB

Purpose

Display the options for external clock synchronization for SCB.

Action

Execute the show command at [edit chassis] hierarchy level.

Display the External Clock Synchronization Configuration for SCBE

Purpose

Display the options for external clock synchronization for SCBE. Note that the SCBE has only one external interface.

Action

Execute the show command at [edit chassis] hierarchy level.

Display the External Clock Synchronization Configuration for SCBE2

Purpose

Display the options for external clock synchronization for SCBE2. SCBE2 has two external interfaces, external-0/0 and external-1/0.

Action

Execute the show command at [edit chassis] hierarchy level.

Displaying the External Clock Synchronization Configuration for MX2020 Control Board

Purpose

Display the options for external clock synchronization for MX2020 Control Board. MX2020 Control Board has two external interfaces, external-a and external-b.

Action

Execute the show command at [edit chassis] hierarchy level.