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Cisco ONS 15600 Reference Manual, R7.2
Chapter 7 Circuits and Tunnels
7.10.1 Bandwidth Allocation and Routing
7.10.1 Bandwidth Allocation and Routing
Within a given network, CTC routes circuits on the shortest possible path between source and destination
based on the circuit attributes, such as protection and type. CTC considers using a link for the circuit
only if the link meets the following requirements:
•
The link has sufficient bandwidth to support the circuit.
•
The link does not change the protection characteristics of the path.
•
The link has the required time slots to enforce the same time slot restrictions for BLSR.
If CTC cannot find a link that meets these requirements, an error appears.
7.10.2 Secondary Sources and Destination
CTC supports secondary sources and destinations (drops). Secondary sources and destinations typically
interconnect two third-party networks, as shown in Figure 7-6. Traffic is protected while it traverses a
network of ONS 15600s.
Figure 7-6 Secondary Sources and Drops
Several rules apply to secondary sources and destinations:
•
CTC does not allow a secondary destination for unidirectional circuits because you can specify
additional destinations after you create the circuit.
•
Primary and secondary sources should be on the same node.
•
Primary and secondary destinations should be on the same node.
•
Secondary sources and destinations are permitted only for regular STS connections.
For bidirectional circuits, CTC creates a path protection connection at the source node that allows traffic
to be selected from one of the two sources on the ONS 15600 network. If you check the Fully Path
Protected option during circuit creation, traffic is protected within the ONS 15600 network. At the
destination, another path protection connection is created to bridge traffic from the ONS 15600 network
to the two destinations. A similar but opposite path exists for the reverse traffic flowing from the
destinations to the sources.
For unidirectional circuits, a path protection drop-and-continue connection is created at the source node.
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Primary source
Secondary source
Primary destination
Secondary destination
Vendor A
network
Vendor B
network
ONS 15600 network