Bandwidth Allocation And Routing; Secondary Sources And Destination; Figure 7-6 Secondary Sources And Drops - Cisco ONS 15600 Reference Manual

7.9.1 Bandwidth Allocation and Routing

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7.9.1 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:
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If CTC cannot find a link that meets these requirements, an error appears.

7.9.2 Secondary Sources and Destination

CTC supports secondary sources and destinations (drops). Secondary sources and destinations typically
interconnect two third-party networks, as shown in
network of ONS 15600s.
Figure 7-6
Secondary source
Several rules apply to secondary sources and destinations:
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Cisco ONS 15600 Reference Manual, R6.0
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If you do not choose fully path protected during circuit creation, circuits can still contain protected
segments. Because circuit routing always selects the shortest path, one or more links and/or
segments can have some protection. CTC does not look at link protection while computing a path
for unprotected circuits.
Circuit routing does not use links that are down. If you want all links to be considered for routing,
do not create circuits when a link is down.
Circuit routing computes the shortest path when you add a new drop to an existing circuit. It tries to
find the shortest path from the new drop to any nodes on the existing circuit.
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.
Secondary Sources and Drops
Primary source
Vendor A
network
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.
Figure 7-6. Traffic is protected while it traverses a
ONS 15600 network
Chapter 7 Circuits and Tunnels
Primary destination
Vendor B
network
Secondary destination