NOTE: The default setting is QL disable.
•
QL enabled—In this mode, the best clock is selected based on the incoming ESMC
SSM QL as long as the incoming QL is at least as good as the source’s configured QL.
If the QLs are equal, the clock selection is based on the configured priority. If both the
received QL and the priority are equal, one of the sources is selected randomly.
Selection Mode for the Incoming ESMC Quality
Depending on the configuration, the clock source selection algorithm uses the configured
or received ESMC SSM quality level for clock selection. In both configured and received
selection modes, 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.
Related
Documentation
External Clock Synchronization Overview for ACX Series Routers on page 226•
• Configuring External Clock Synchronization for ACX Series Routers on page 228
• synchronization on page 1739
Clock Sources
Clocking is an important feature on the ACX Series routers. The ACX Series routers can
be directly connected to different types of base stations (for example, base transceiver
station (BTS) in 2G, NodeB in 3G, and eNodeB in 4G networks) and different types of
routers that hand off time-division multiplexing (TDM, ATM, and Ethernet traffic to the
base station controller. ACX Series routers must extract the network clock from these
sources and pass on synchronization information to the base stations to help the routers
synchronize with the base station controller.
The ACX Series router timing hardware includes two external clock inputs (BITS and
GPS), T1 and E1 ports (FPC 0, PIC 0), Gigabit Ethernet ports (RJ45), Gigabit Ethernet
ports (SFP), and 10-Gigabit Ethernet ports.
NOTE: ACX500 routers do not support TDM, BITS, ATM, T1 or E1, SONET,
and 10-Gigabit Ethernet interfaces.
ACX Series router hardware and software support various clocking options:
•
The ACX series has an OCXO (Stratum 3E) type of oscillator.
•
External clocking includes PPS, a choice of GPS-based clock recovery (10 MHz), or
BITS-T1 or E1 line synchronization (1.544 MHz and 2.048 MHz).
225Copyright © 2017, Juniper Networks, Inc.
Chapter 9: Configuring Timing and Synchronization
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