User guide
3-18
Configuration Guide for Cisco DSLAMs with NI-2
OL-2074-03
Chapter 3 Initially Configuring the Cisco DSLAM
Configuring Network Clocking
Priority 2 clock source: No clock
Priority 3 clock source: No clock
Priority 4 clock source: No clock
Priority 5 clock source: System clock
Current clock source:System clock, priority:5
Nettime Config Register Contents:
NDIV:FF SRC:2, SLOCK:0, TLOCK:0, NFAIL:0, E1:0, NSEL:0
Trunk LED Register CLK_SEL:3
BITS Register Contents:
CR1: CB, CR2: 0, CR3: 0, ICR: 0, TSR: C1, PSR: 31, ESR: 77, CR4: 0
BITS Source configured as: T1 Short Haul, 0-133ft/0.6db pulse, 100 ohm cable, 1n
This example displays the clock source configuration of ATM 0/2:
DSLAM# show running-config interface atm 0/2
Building configuration...
Current configuration : 62 bytes
!
interface ATM0/2
no keepalive
atm manual-well-known-vc
atm access-group tod1 in
atm pvc 0 35 rx-cttr 3 tx-cttr 3 interface ATM0/2 0 any-vci encap qsaal
atm route-optimization soft-vc interval 360 time-of-day 18:0 5:0
clock-source network-derived
!
Providing Clock Synchronization Services
Any module in a DSLAM chassis capable of receiving and distributing a network timing signal can
propagate that signal to any similarly capable module in the chassis. These modules are capable of
receiving and distributing a primary reference source (PRS) for the clock:
• A BITS clock through the I/O card
• An OC-3 in a DSLAM chassis
• A quad DS3 module in a DSLAM chassis that derives the clock from the trunk interface
Note A trunk port can propagate a clocking signal in either direction.
If you issue the network-clock-select command with the appropriate parameters, you can define a
particular port in a DSLAM chassis (subject to the above limitations) to serve as the source of a PRS for
the entire chassis or for other devices in the networking environment. This command is described in the
“Configuring Network Clock Priorities and Sources” section on page 3-16.
You can also use the network-clock-select command to designate a particular port in a DSLAM chassis
to serve as a master clock source for distributing a single clocking signal throughout the chassis or to
other network devices. You can distribute this reference signal in any location the network needs to
globally synchronize the flow of constant bit rate (CBR) data.