Cisco Cisco ONS 15454 SONET Multiservice Provisioning Platform (MSPP) Guía De Diseño

OL-4556-01

BITS input pins on the backplane of Node 1. 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 Access Multiplexer.

In the example, Slots 5 and 6 contain the OC-N trunk cards in each node. Timing at Nodes 2, 3,
and 4 is set to line, and the timing references are set to the port of the trunk OC-N cards based
on distance from the BITS source. NE Reference 1 is set to the port of the OC-N trunk card
closest to the BITS source. At Node 2, the NE Reference 1 is the port of the OC-N card in Slot 5,
because it is connected to Node 1. At Node 4, the NE Reference 1 is set to the port of the OC-N
card in Slot 6, because it is connected to Node 1. At Node 3, the NE Reference 1 could be the
port of either OC-N trunk card because they are equal distance from Node 1.

Figure 2-19: An ONS 15454 Network Timing Example

Failure Switching

Depending on the network condition, the ONS 15454 will operate in one of the following
synchronization modes.

Normal Mode

: The system clock is synchronized to a reference source. The output frequency of

the clock is the same as the input reference frequency over the long term. The Sync LED on the
TCC card indicates Normal Mode.

Fast Start Mode

: Used for fast pull-in of a reference clock, Fast Start is active when the internal

reference frequency is offset from the external reference clock. If the frequency is offset by more