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synchronization (MX Series)

Syntax

Hierarchy Level

Release Information

Statement introduced in Junos OS Release 10.4.

Options interfaces, output, and source interfaces external introduced in Junos OS Release 12.3.

Description

(MX5-T, MX10-T, MX40-T, MX80-T, MX240, MX480, and MX960 routers) Configure Synchronous Ethernet parameters. For configuration details, see Configuring Clock Synchronization Interface for MX Series Routers.

(MX240, MX480, and MX960 routers with Enhanced MX SCB) Configure centralized clocking parameters.

• Starting in Junos 12.2, configure distribution of the selected chassis clock source to downstream network elements through supported line interfaces.
• Starting in Junos 12.3, configure an external building-integrated timing supply (BITS) timing source. You can also configure the selected chassis clock, or an incoming Synchronous Ethernet or PTP line source for transmission out the external interface.

For configuration details, see Example: Configuring Centralized Clocking on the Enhanced MX Switch Control Board.

Note: Unified ISSU is not supported when clock synchronization is configured for Synchronous Ethernet.

Options

clock-mode (auto-select | free-run)—Specify the mode of operation to select the clock source either from a free-run local oscillator or from an external qualified clock. On MX240, MX480, and MX960 routers with enhanced MPCs, the free-run clock is provided by a local oscillator. On other MX Series routers, the free-run clock is provided by the SCB. The default setting is auto-select mode.

esmc-transmit interfaces (all | interface-name)—Enable Ethernet Synchronization Message Channel (ESMC) packet transmission.

• configuration-change—Clock select wait time after change in configuration. The range is 15 through 60 seconds. The default is ???
• restart— Clock select wait time after reboot. The range is 60 through 180 seconds. The default is 120 seconds.
• switchover— Switchover wait time after clock recovery. The range is 30 to 60 seconds. The default is 30 seconds.

interfaces external—(Enhanced MX SCB only) Configure the external interface for operating with a connected external device. This interface can be configured as a clock source, which then becomes a candidate for selection as the chassis clock source by the clock source selection algorithm.

• signal-type (2048khz | e1 | t1)—Specify the external interface signal type:
  • 2048khz—2048-KHz clock signal
  • e1—E1-coded 2048-KHz signal on 120-ohm balanced line
  • t1—T1-coded 1.544-MHz signal on 100-ohm balanced line
• e1-options—Specify the E1 options:
  • framing (g704 | g704-no-crc4)—Specify the framing format:
    • g704—G.704 framing format for E1 interfaces
    • g704-no-crc4—G.704 framing with no CRC4 for E1 interfaces
  • line-encoding (ami | hdb3)—Specify the line encoding:
    • ami— Alternate mark inversion (AMI)
    • hdb3—High-d Density bipolar 3 code (HDB3)
  • sabit number—Specify the San synchronization status bit used for exchanging SSN quality. The value can be 4, 5, 6, 7, or 8. The default is 4.
• t1-options—Specify the T1 options:
  • framing (esf | sf)—Specify the framing format:
    • esf—Extended superframe (ESF)
    • sf—Superframe (SF)
  • line-encoding (ami | b8zs)—Specify the line encoding:
    • ami— Alternate mark inversion (AMI)
    • b8zs—8-bit zero suppression, bipolar with 8-zero substitution (B8ZS)

network-option (option-1 | option-2)—Specify the synchronization networking:

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

output interfaces external—(Enhanced MX SCB only) Specify the properties of the external output interface:

• holdover-mode-disable—Disable holdover.
• minimum-quality (prc | prs | sec | smc | ssu-a | ssu-b | st2 | st3 | st3e | st4 | stu | tnc)—Specify the minimum quality level threshold for selection of this clock (see Table 1). If the quality level of the output clock source drops below the configured minimum quality level threshold, the external output clock is squelched.

  • Table 1: Quality Levels

    Quality Level	Description
    prc	Timing quality of a primary reference clock (option-1 only).
    prs	Clock traceable to a primary reference source (option-2 only).
    sec	Timing quality of an SDH equipment clock (option-1 only).
    smc	Clock traceable to a self-timed SONET (option-2 only).
    ssu-a	Timing quality of a type I or IV slave clock (option-1 only).
    ssu-b	Timing quality of a type VI slave clock (option-1 only).
    st2	Clock traceable to Stratum 2 (option-2 only).
    st3	Clock traceable to Stratum 3 (option-2 only).
    st3e	Clock traceable to Stratum 3E (option-2 only).
    st4	Clock traceable to Stratum 4 free-run (option-2 only).
    stu	Clock traceable to an unknown quality (option-2 only).
    tnc	Clock traceable to a transit node clock (option-2 only).

• source-mode (chassis | line)—Specify source mode for selecting source to output:
  • chassis—Chassis clock for output
  • line—Best line clock source for output
• tx-dnu-to-line-source-enable—Set Tx QL to DNU/DUS on line source interface that has been selected as the external output source.
• wander-filter-disable—Disable wander filtering.

quality-mode-enable—Specify the clock selection, quality level, and priority setting. The quality level (QL) parameter for a Synchronous Ethernet interface is optional when quality mode is enabled and the selection mode is set to received-quality. The default QL for a Synchronous Ethernet interface is based on the value of network-option: option-1 selects SEC and option-2 selects ST3. Table 2 shows whether SSM QL is supported for a given external interface signal type and framing. The default setting is disabled.

• Table 2: SSM-QL Support by Signal Type and Framing

  Signal Type	Framing	SSM QL Supported
  E1	G.704	yes
  E1	G.704 no CRC4	no
  T1	ESF	yes
  T1	SF	no
  2048 KHz	Not applicable	no

• 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.

• priority number—Specify a priority level from 1 to 5. When not specified, external-a has higher default priority than external-b, and external-b has higher default priority than other Gigabit Ethernet or 10-Gigabit Ethernet clock sources, which have the lowest default priority. Any priority you configure is higher than any default priority.

• quality-level (prc | prs |sec | smc | ssu-a | ssu-b | st2 | st3 | st3e | st4 | stu | tnc)—Specify the quality-level option based on the configured network-option. For quality level details, see Table 1.

  Note: Starting with Junos OS Release 12.2R1, the quality-level parameter for a Synchronous Ethernet interface is optional when quality mode is enabled and the selection mode is set to received 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.

  • Both option I and option II SSM quality levels (QL) are supported:

    • For option-1, QL must be configured for external clocks (external-a or external-b) whether or not QL is enabled.
    • For option-2, the default QL for external clocks is QL_STU whether or not QL is enabled.
  • QL is set to DNU for network-option 1 and set to DUS for network-option 2, if quality-level is not configured and no ESMC messages are received.
  • On the selected active source (primary or secondary, whichever 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 sources of Ethernet interface type to avoid source looping.
• request force-switch—Force a switch to this source if the source is enabled and not locked out. You can configure only one source to be force-switched.
• request lockout—You can configure lockout for any source. When configured, this source is not considered by the clock selection process.
• wait-to-restore minutes—(interfaces only) Specify a time for each port to be up before opening the ESMC—from 0 through 12 minutes. 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 clock selection process.

• In revertive mode (the default), the system switches from a lower to a higher quality clock source whenever the higher quality clock source becomes available.
• In non-revertive mode, the system continues to use the current clock source as long as it is valid.

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.