Specifications

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Cisco ONS 15454 Installation and Operations Guide, R3.2
March 2002
Chapter 3 Node Setup
Setting Up ONS 15454 Timing
b. In the Selected Group section, verify that the protect card is in standby mode. If it is in standby
mode, continue with Step 3. If it is active, complete Step c.
c. If the working card is in standby mode, manually switch traffic back to the working card. In the
Selected Group pane, click the working card, then click Manual. Verify that the protect card
switches to standby mode and the working card is active. If it does, continue with Step 3. If the
protect card is still active, do not continue. Begin troubleshooting procedures or call technical
support.
Step 3 From the node view, click the Provisioning > Protection tabs.
Step 4 In the Protection Groups section, click a protection group.
Step 5 Click Delete.
3.6 Setting Up ONS 15454 Timing
SONET timing parameters must be set for each ONS 15454. Each ONS 15454 independently accepts its
timing reference from one of three sources:
• The BITS (Building Integrated Timing Supply) 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 TCC+ 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 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 GPS signal.
• The other nodes are set to line. The line nodes derive timing from the externally-timed node through
the OC-N trunk cards.
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 the internal clock provided on every ONS 15454 TCC+ card. This clock is a Stratum
3 (ST3). If an ONS 15454 becomes isolated, timing is maintained at the ST3 level.
Caution Mixed timing allows you to select both external and line timing sources. However, Cisco does not
recommend its use because it can create timing loops. Use this mode with caution.
3.6.1 Network Timing Example
Figure 3-8 shows an ONS 15454 network timing setup example. Node 1 is set to external timing. Two
timing references are set to BITS. These are Stratum 1 timing sources wired to the BITS input pins on
the Node 1 backplane. 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.