Cisco Systems ONS 15600 manual Network Timing

Chapter 6 Timing

6.2 Network Timing

6.2 Network Timing

Figure 6-1shows an ONS 15600 network timing example. Node 1 is set to external timing. Two timing references 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. In the event of a failure of one of the TSC modules, the redundant TSC module provides timing for BITS out. There are some restrictions on the provisioning of BITS out:

If the system is BITS timed:

•BITS-1 Out can have one reference if a 1+1 protected pair is chosen or two references can be selected if unprotected line sources are chosen.

•BITS-2 Out can have one reference if a 1+1 protected pair is chosen or two references can be selected if unprotected line sources are chosen.

If system is LINE timed:

•BITS-1 Out can have one unprotected line source and either or both of the NE references.

•BITS-2 Out can have one unprotected line source and either or both of the NE references. If the system is in mixed mode:

•BITS-1 Out can have one unprotected line source and any line source selected as NE reference Ref-1 or Ref-2.

•BITS-2 Out can have one unprotected line source and any line source selected as NE reference Ref-1 or Ref-2.

In the example, Slots 11 and 12 of Node 1 contain the trunk (span) cards. Timing at Nodes 2, 3, and 4 is set to line, and the timing references are set to the trunk cards according to the distance from the BITS source. Reference 1 is set to the trunk card closest to the BITS source. At Node 2, Reference 1 is Slot 11/Port 1 because it is connected to Node 1. At Node 4, Reference 1 is set to Slot 12/Port 1 because it is connected to Node 1. At Node 3, Reference 1 could be either trunk card because they are an equal distance from Node 1.

Cisco ONS 15600 Reference Manual, R7.2

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