Chapter 10 Timing - Cisco ONS 15454 Reference Manual

10.2 10.2 Network Timing
Mixed timing allows you to select both external and line timing sources. However, Cisco does not
Caution
recommend its use because it can create timing loops. Use this mode with caution.
10.2 Network Timing
Figure 10-1
timing references are set to BITS. These are Stratum 1 timing sources wired to the BITS input pins on
the Node 1 backplane. The third reference is set to internal clock. The BITS output pins on the backplane
of Node 3 are used to provide timing to outside equipment, such as a digital access line multiplexer.
In the example, Slots 5 and 6 contain the trunk (span) cards. Timing at Nodes 2, 3, and 4 is set to line,
and the timing references are set to the trunk cards based on distance from the BITS source. Reference 1
is set to the trunk card closest to the BITS source. At Node 2, Reference 1 is Slot 5 because it is
connected to Node 1. At Node 4, Reference 1 is set to Slot 6 because it is connected to Node 1. At
Node 3, Reference 1 could be either trunk card because they are an equal distance from Node 1.
Figure 10-1
Node 4
Timing Line
Ref 1: Slot 6
Ref 2: Slot 5
Ref 3: Internal (ST3)
Cisco ONS 15454 Reference Manual, R7.0.1
10-2
shows an ONS 15454 network timing setup example. Node 1 is set to external timing. Two
ONS 15454 Timing Example
Slot 6
Slot 5
BITS1 BITS2
source source
Node 1
Timing External
Ref 1: BITS1
Ref 2: BITS2
Ref 3: Internal (ST3)
Slot 5 Slot 6
Slot 5
Slot 6
Slot 6
Slot 5
Node 3
Timing Line
BITS1 BITS2 Ref 1: Slot 5
Ref 2: Slot 6
out out
Ref 3: Internal (ST3)
Third party
equipment
Chapter 10 Timing
Node 2
Timing Line
Ref 1: Slot 5
Ref 2: Slot 6
Ref 3: Internal (ST3)
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