Datasheet

CHAPTER
10-1
Cisco ONS 15454 SDH Reference Manual, R7.0
October 2008
10
Timing
This chapter provides information about Cisco ONS 15454 SDH users and SDH timing. To provision
security and timing, refer to the Cisco ONS 15454 SDH Procedure Guide.
Chapter topics include:
• 10.1 Timing Parameters, page 10-1
• 10.2 Network Timing, page 10-2
• 10.3 Synchronization Status Messaging, page 10-3
10.1 Timing Parameters
SDH timing parameters must be set for each ONS 15454 SDH. Each ONS 15454 SDH independently
accepts its timing reference from one of three sources:
• The building integrated timing supply (BITS) pins on the MIC-C/T/P coaxial connectors.
Note For more information on BITS timing, see the “2.3.1 TCC2P Functionality” section on
page 2-10.
• An STM-N card installed in the ONS 15454 SDH. The card is connected to a node that receives
timing through a BITS source.
• The internal ST3 clock on the TCC2/TCC2P card.
You can set ONS 15454 SDH timing to one of three modes: external, line, or mixed. If timing is coming
from the BITS pins, set the ONS 15454 SDH timing to external. If the timing comes from an STM-N
card, set the timing to line. In typical ONS 15454 SDH networks:
• One node is set to external. The external node derives its timing from a BITS source wired to the
BITS MIC-C/T/P coaxial connectors. 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 STM-N trunk (span) cards. The MSTP normally derives timing from the line using an OSCM or
OSC-CSM card located inside an STM-1 channel.
You can set three timing references for each ONS 15454 SDH. 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 SDH TCC2/TCC2P