Timing Parameters - Cisco ONS 15454 Reference Manual

Timing
This chapter provides information about Cisco ONS 15454 SONET timing. To provision timing, refer to
the Cisco ONS 15454 Procedure Guide.
Chapter topics include:
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10.1 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 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.
However, if you assign all three references to other timing sources, the internal clock is always available
as a backup timing reference. The internal clock is a Stratum 3 (ST3), so if an ONS 15454 node becomes
isolated, timing is maintained at the ST3 level.
The CTC Maintenance > Timing > Report tabs show current timing information for an ONS 15454,
including the timing mode, clock state and status, switch type, and reference data.
OL-9217-01
10.1 Timing Parameters, page 10-1
10.2 Network Timing, page 10-2
10.3 Synchronization Status Messaging, page 10-3
The building integrated timing supply (BITS) pins on the ONS 15454 backplane.
An OC-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 trunk (span) cards.
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Cisco ONS 15454 Reference Manual, R7.0.1
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