Cisco ONS 15454 DWDM - Page 967

CHAPTER
21-1
Cisco ONS 15454 DWDM Installation and Operations Guide, R6.0
August 2005
21
Timing Reference
This chapter provides information about Cisco ONS 15454 users and node timing. To provision security
and timing, see the “NTP-G23 Create Users and Assign Security” procedure on page 3-5.
Note Unless otherwise specified, “ONS 15454” refers to both ANSI and ETSI shelf assemblies.
Chapter topics include:
• 21.1 Node Timing Parameters, page 21-1
• 21.2 Network Timing, page 21-2
• 21.3 Synchronization Status Messaging, page 21-3
21.1 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:
• 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.
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:
• 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. 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.
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.