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Configuring Clock Synchronization Interface for MX Series Routers

MX5-T, MX10-T, MX40-T, MX80, MX80-T, MX240, MX480, and MX960 routers support external clock synchronization using Synchronous Ethernet.

Configuring external clock synchronization requires making clock selection, quality level (QL), and priority considerations. The clock selection algorithm is used to pick the two best clock sources, primary and secondary, from among all the various sources, based on system configuration and execution criteria such as QL, priority, hardware restrictions, and so on, and is achieved using the following logic and restrictions:

  • QL must be configured for non-external clocks, whether or not QL is enabled.
  • In the case of option-1, QL must be configured for external clocks (external-a or external-b), whether or not QL is enabled.
  • In the case of option-2, the default QL for the external clocks is QL_STU, whether or not QL is enabled.
  • Starting with Junos OS Release 12.2R1, the quality level (QL) parameter for a Synchronous Ethernet interface is optional when quality-mode is enabled and the selection-mode is set to receive-quality. The default QL for a Synchronous Ethernet interface is SEC for the option-1 network type and ST3 for the option-2 network type.
  • When QL is enabled, the received QL must be equal to or better than the configured QL for that particular source or else that source will not be considered for clock selection. This is so that a downstream client is guaranteed clock quality of a certain level (that ‘certain level’ being the configured QL).
  • Configuring priority is optional. When not specified, external-a has a higher default priority than external-b, and external-b has a higher default priority than Ethernet based sources such as ge or xe clock sources, which have the lowest default priority. Configured priority is higher than any default priority.
  • The 10-Gigabit Ethernet MIC with XFP supports Synchronous Ethernet, which requires both the MIC and interface configured in LAN framing mode. In LAN mode, the LAN frequency is directly supplied by the MIC's on-board clocking circuitry.

  • During clock selection:

    • The active source with highest QL is selected.
    • If QL is the same for two or more sources, then the source with highest priority wins.
    • If two or more sources have the same QL and priority, then currently active source, if any, among these sources wins.
    • If two or more sources have the same QL and priority, and none of these is currently active, then any one of these may be picked.
    • The configured (or default) QL of the selected clock source is used for Ethernet Synchronization Messaging Channel (ESMC).
    • If the primary clock source is ge|xe-x/y/z, where y is even (0 or 2), then the secondary cannot be ge|xe-x/y/* or ge|xe-x/y + 1/*. E.g., if ge-1/2/3 is the primary clock source, then the secondary cannot be ge-1/2/* or ge-1/3/* for an MX80 or MX240 router.
    • If the primary clock source is ge|xe-x/y/z, where y is odd (1 or 3), then the secondary cannot be ge|xe-x/y/* or ge|xe-x/y - 1/*. E.g., if xe-2/3/4 is the primary, then the secondary cannot be xe-2/2/* or xe-2/3/* for an MX80 or MX240 router.
    • If the primary clock source is ge|xe-x/y/z, then the secondary cannot be ge|xe-x/y/* in the case of 12-16x10G DPC on an MX Series router e.g., if ge-0/1/2, is primary, then ge-0/1/* cannot be the secondary clock source, but ge-0/0/* may be the secondary.
    • In order to receive or transmit ESMC messages out of an interface, at least one logical interface should be configured on that interface. If the interface is currently not configured with a logical interface, you may do so using the set interfaces interface-name unit 0 statement at the edit hierarchy level.

Setting the clock type

To set the clock type, use the following command:

set chassis synchronization network-option (option-1 | option-2)

EEC-1 maps to G.813 option 1 and EEC-2 maps to G.812 type IV clock.

Setting the clock mode

To set the mode of operation to select the clock source either from free-run local oscillator or from an external qualified clock, use the following command:

set chassis synchronization clock-mode (free-run | auto-select)

For MX80 routers, the free-run clock is provided by the local oscillator..

For MX240 routers, the free-run clock is provided by the SCB..

The default for both routers is auto-select mode.

Setting the quality mode

To set the synchronization quality mode, use the following command:

set chassis synchronization quality-mode-enable

The default is disable.

Setting the selection mode

To configure the ESMC or SSM quality-based clock selection mode, use the following command:

set chassis synchronization selection-mode (configured-quality|received-quality)

When the selection-mode statement is set as configured-quality, the clock source selection algorithm uses the ESMC or SSM quality level configured for a qualifying interface.

When the selection-mode statement is set as received-quality, the clock source selection algorithm uses the ESMC or SSM quality level received on the qualifying interface.

Note: For the selection-mode statement configuration to take effect, you must set the quality-mode-enable statement at the [edit chassis synchronization] hierarchy level.

Setting the switchover, config-change, or reboot times

To set the switchover, configuration-change, or restart time, use the following command:

set chassis synchronization hold-interval (configuration-change | restart | switchover) seconds

This sets the time interval to wait before selecting the new clock source during.

The default switchover time is 30 seconds and cold boot time is 120 seconds.

Setting the synchronization switching mode

To set the synchronization switchover mode, use the following command:

set chassis synchronization switchover-mode (revertive | non-revertive)

In revertive mode, the system switches from a lower to a higher quality clock source whenever the higher clock source becomes available.

In non-revertive mode, the system continues to use the current clock source as long as it is valid.

The default mode is revertive.

Setting the clock source

To set the clock source, use the following command:

set chassis synchronization source (external-a | external-b | interfaces interface-name)

The clock source is specified using the clock selection process.

Setting ESMC packet transmit

To enable ESMC packet transmit, use the following command:

set chassis synchronization esmc-transmit interfaces interface-name

Setting the synchronization source quality level

To set the synchronization source quality level, use the following command:

set chassis synchronization source (external-a | external-b | interfaces interface-name) quality-level (prc | prs |sec | smc | ssu-a | ssu-b | st2 | st3 | st3e | st4 | stu | tnc)

Both option I and option II SSM quality levels are supported.

The quality level is set to DNU for network-option 1 and set to DUS for network-option 2, if quality-level not configured and no ESMC messages received.

On selected active source (primary or secondary which is active), even if ESMC transmit is not enabled, a DNU ESMC will be sent out if network-option is 1, and DUS ESMC will be sent out if network-option is 2. This is applicable only for Ethernet interface type sources. This is done to avoid the source looping, as per the standard requirement.

Setting the synchronization source priority

To set the synchronization source priority, use the following command:

set chassis synchronization source (external-a | external-b | interfaces interface-name) priority number

Setting the synchronization source wait to restore time

To set the synchronization source wait to restore time, use the following command:

set chassis synchronization source interfaces interface-name wait-to-restore minutes

A wait-to-restore time can be configured for each port. When a port’s signal transitions out of the signal fail state it must be fault free for the wait-to-restore time before it is again considered by the selection process.

The range is from 0 through 12 minutes.

The default time is 5 minutes.

Setting the synchronization source lockout

To set the synchronization source lockout, use the following command:

set chassis synchronization source (external-a | external-b | interfaces interface-name) request lockout

Lockout may be configured for any source. When configured, that source will not be considered by the selection process.

Setting the forced switch

To set the forced switch, use the following command:

set chassis synchronization source (external-a | external-b | interfaces interface-name) request force-switch

Forces a switch to the source provided the source is enabled and not locked out. Only one configured source may be force-switched.

Setting the MIC level framing mode for the 10-Gigabit Ethernet MIC with XFP

To configure the LAN framing mode on the 10-Gigabit Ethernet MIC with XFP, use the following command:

set chassis fpc fpc-slot pic pic-slot framing <lan>

Operation in LAN framing mode on the 10-Gigabit Ethernet MIC with XFP also requires interface framing mode configuration of the MIC interface.

Setting the interface framing mode for the 10-Gigabit Ethernet MIC with XFP

To configure the interface framing mode on the 10-Gigabit Ethernet MIC with XFP, use the following command:

set interfaces xe-fpc/pic/port framing-mode <lan-phy | wan-phy>

Operation in LAN framing mode on the 10-Gigabit Ethernet MIC with XFP also requires MIC level framing mode configuration.

To verify the configuration, see Example: Configuring Synchronous Ethernet on MX Series Routers.

 

Related Documentation

 

Published: 2013-03-07

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