Cisco ONS 15454 DWDM Reference Manual page 559

Timing Reference
This chapter provides information about Cisco ONS 15454 users and node timing. To provision timing,
refer to the Cisco ONS 15454 DWDM Procedure Guide.
Unless otherwise specified, "ONS 15454" refers to both ANSI and ETSI shelf assemblies.
Note
Chapter topics include:
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14.1 Node Timing Parameters
SONET timing parameters must be set for each ONS 15454. Each ONS 15454 independently accepts its
timing reference from one of three sources:
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You can set ONS 15454 timing to one of three modes: external, line, or mixed. If timing is coming from
the BITS pins, set ONS 15454 timing to external. If the timing comes from an OC-N/STM-N card, set
the timing to line. In typical ONS 15454 networks:
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You can set three timing references for each ONS 15454. The first two references are typically two
BITS-level sources, or two line-level sources optically connected to a node with a BITS source. The third
reference is usually assigned to the internal clock provided on every ONS 15454 TCC2/TCC2P card.
78-18343-02
14.1 Node Timing Parameters, page 14-1
14.2 Network Timing, page 14-2
14.3 Synchronization Status Messaging, page 14-3
The building integrated timing supply (BITS) pins on the ONS 15454 backplane (ANSI) or
MIC-C/T/P coaxial connectors (ETSI).
An OC-N/STM-N card installed in the ONS 15454. The card is connected to a node that receives
timing through a BITS source.
The internal ST3 clock on the TCC2/TCC2P card.
One node is set to external. The external node derives its timing from a BITS source wired to the
BITS backplane pins. The BITS source, in turn, derives its timing from a primary reference source
(PRS) such as a Stratum 1 clock or global positioning satellite (GPS) signal.
The other nodes are set to line. The line nodes derive timing from the externally timed node through
the OC-N/STM-N trunk (span) cards. The DWDM node normally derives timing from the line using
the OSCM or OSC-CSM card that are inside an OC-3/STM-1 channel.
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C H A P T E R
Cisco ONS 15454 DWDM Reference Manual, R8.5
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