Configuring External Clock Synchronization for ACX Series Routers
The ACX Series Universal Metro 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 (QL), and priority considerations. The clock source selection algorithm is used to pick the two best upstream clock sources from among all the various sources, based on system configuration and execution criteria such as QL, priority, and hardware restrictions.
To configure external synchronization on the router, include
the synchronization statement at the [edit chassis] hierarchy level.
Setting the Ethernet equipment clock (EEC) network type
The network type options set the frequency of the configured clock. When bits is configured with option-1 on the ACX router, the Synchronous Ethernet equipment is optimized for 2048 Kbps, the speed of an E1 interface. When bits is configured with option-2 on the ACX router, the Synchronous Ethernet equipment is optimized for 1544 Kbps, the speed of a T1 interface. To set the clock type, use the following command:
set chassis synchronization network-option (option-1 | option-2)
For option-1, QL must be configured for external clocks (gps or bits) whether or not QL is enabled. For option-2, the default QL for external clocks is QL_STU whether or not QL is enabled.
The following output shows an example of the configuration of the network type with option-1:
[edit]
user@host# show chassis
synchronization {
network-option option-1;
}Setting the clock mode
Clock mode sets the selection of the clock source from a free-running local oscillator or from an external qualified clock. The default clock mode is auto-select, which uses the best clock source. To set the clock mode, use the following command:
set chassis synchronization clock-mode (free-run | auto-select)
The following output shows an example of the configuration of the free-run option:
[edit]
user@host# show chassis
synchronization {
clock-mode free-run;
}Automatic clock selection does not apply to the IEEE 1588v2 recovered clock.
Setting the quality mode
Specify the expected quality of the incoming clock on this source. The default is disable. To set the synchronization quality mode, use the following command:
set chassis synchronization quality-mode-enable
The following output shows the configuration of the quality-mode-enable statement:
[edit]
user@host# show chassis
synchronization {
quality-mode-enable;
}Setting the selection mode
The selection mode specifies whether the clock source selection algorithm should use the configured or received ESMC SSM quality level for clock selection. In both selection modes (configured-quality and received-quality), the interface qualifies for clock source selection only when the received ESMC SSM quality level on the interface is equal to or greater than the configured ESMC SSM quality level for the interface. To configure the ESMC SSM quality-based clock source selection mode, use the following command:
set chassis synchronization selection-mode (configured-quality | received-quality)
The following output shows the configuration of the selection-mode statement with the configured-quality option and the mandatory quality-mode-enable statement:
[edit]
user@host# show chassis
synchronization {
selection-mode configured-quality;
quality-mode-enable;
}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 time interval before a new clock source is selected
For routers operating with Synchronous Ethernet , set the time interval to wait before the router selects a new clock source. After a change in the configuration, the time to wait is between 15 and 60 seconds. After a reboot (restart), the time to wait is from 60 to 180 seconds. After clock recovery (switchover), the time to wait is from 30 to 60 seconds. The default switchover time is 30 seconds and cold boot time is 120 seconds. To set the time interval before a new clock source is selected, use the following command:
set chassis synchronization hold-interval (configuration-change | restart | switchover) seconds
The following output shows the configuration of the hold-interval statement with the configuration-change option:
[edit]
user@host# show chassis
synchronization {
hold-interval {
configuration-change 20;
}
}Setting the synchronization switching mode
The configured switching mode determines the clock source used. 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. To set the synchronization switchover mode, use the following command:
set chassis synchronization switchover-mode (revertive | non-revertive)
The following output shows the configuration of the switchover-mode statement with the non-revertive option:
[edit]
user@host# show chassis
synchronization {
switchover-mode non-revertive;
}Setting the clock source
The configured clock source is the candidate for selection by the clock selection algorithm. The clock source can be the router’s BITS T1 or E1 interface, GPS, or an interface with an upstream clock source. To set the clock source, use the following command:
set chassis synchronization source (bits | gps | interfaces interface-name)
The following output shows the configuration of the source statement with the bits option and the mandatory network-option statement. When bits is configured with option-1 on the ACX2000 router, the Synchronous Ethernet equipment is optimized
for 2048 Kbps, the speed of an E1 interface.
[edit]
user@host# show chassis
synchronization {
network-option option-1;
source {
bits;
}
}For the source statement configuration to take
effect, you must set the network-option (option-1 | option-2) statement at the [edit chassis synchronization] hierarchy
level.
The bits option is not supported on the ACX1000 router.
Setting ESMC transmit interface
The ESMC transmit interface is the interface on which ESMC transmit messages are permitted. To enable ESMC packet transmit, use the following command:
set chassis synchronization esmc-transmit interfaces interface-name
The following output shows the configuration of the esmc-transmit statement:
[edit]
user@host# show chassis
synchronization {
esmc-transmit {
interfaces ge-0/1/0;
}
}
You can also enable ESMC on all interfaces with the interfaces
all statement at the preceding hierarchy level.
Setting the synchronization source quality level
Specify the expected quality of the incoming clock on this source. Specific quality-level options are valid depending on the configured network-option; option-1 or option-2. Both option-1 and option-2 SSM quality levels are supported. To set the synchronization source quality level, use the following command:
set chassis synchronization source (bits | gps | interfaces interface-name) quality-level (prc | prs |sec | smc | ssu-a | ssu-b | st2 | st3 | st3e | st4 | stu | tnc)
The following output shows the configuration of the quality-level statement configured with the prc option:
[edit]
user@host# show chassis
synchronization {
source {
bits {
quality-level prc;
}
}
}Setting the synchronization source priority
Specify a priority level between 1 and 5. When not specified, gps has a higher priority than bits,and bits has a higher default priority than other Gigabit Ethernet or 10 Gigabit Ethernet clock sources, which have the lowest priority. To set the synchronization source priority, use the following command:
set chassis synchronization source (bits | gps | interfaces interface-name) priority number
The following output shows the configuration of the priority statement:
[edit]
user@host# show chassis
synchronization {
source {
bits {
priority 2;
}
}
}Setting the synchronization source wait to restore time
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.
To set the synchronization source wait-to-restore time, use the following command:
set chassis synchronization source interfaces interface-name wait-to-restore minutes
The following output shows the configuration of the wait-to-restore statement:
[edit]
user@host# show chassis
synchronization {
network-option option-1;
source {
interfaces ge-0/1/0 {
wait-to-restore 2;
}
}
}Setting the synchronization source lockout
A lockout may be configured for any source. When a lockout is configured for a source, that source will not be considered by the selection process. To set the synchronization source lockout, use the following command:
set chassis synchronization source (bits | gps | interfaces interface-name) request lockout
The following output shows the configuration of the request
lockout statement:
[edit]
user@host# show chassis
synchronization {
network-option option-1;
source {
bits {
request lockout;
}
}
}Setting the forced switch
Force a switch to the source provided that the source is enabled and not locked out. Only one configured source may be force-switched. To set the forced switch, use the following command:
set chassis synchronization source (bits | gps | interfaces interface-name) request force-switch
The following output shows the configuration of the request
force-switch statement:
[edit]
user@host# show chassis
synchronization {
network-option option-1;
source {
bits {
request force-switch;
}
}
}