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Appendix A
Circuit Routing
Figure A-2
Secondary source
Several rules apply to secondary sources and drops:
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For bidirectional circuits, CTC creates a UPSR connection at the source node that allows traffic to be
selected from one of the two sources on the ONS 15454 network. If you check the Fully Path Protected
option during circuit creation, traffic is protected within the ONS 15454 network. At the destination,
another UPSR connection is created to bridge traffic from the ONS 15454 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 UPSR drop-and-continue connection is created at the source node.
Manual Circuit Routing
Routing circuits manually allows you to:
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CTC imposes the following rules on manual routes:
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November 2001
Secondary sources and drops
Primary source
Vendor A
network
CTC does not allow a secondary destination for unidirectional circuits because you can always
specify additional destinations (drops) 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
The sources and drops cannot be DS-3, DS3XM, or DS-1 based STS-1s or VTs
Secondary sources and destinations are permitted only for regular STS/VT connections (not for VT
tunnels and multicard EtherSwitch circuits)
For point-to-point (straight) Ethernet circuits, only SONET STS endpoints can be specified as
multiple sources or drops
Choose a specific path, not just the shortest path chosen by automatic routing
Choose a specific STS/VT on each link along the route
Create a shared packet ring for Multicard EtherSwitch circuits
Choose a protected path for Multicard EtherSwitch circuits, allowing virtual UPSR segments
All circuits, except Multicard EtherSwitch circuits in a shared packet ring, should have links with a
direction that flows from source to destination. This is true for Multicard EtherSwitch circuits that
are not in a shared packet ring (see
ONS 15454 network
Figure
A-1).
Cisco ONS 15454 Installation and Operations Guide
Manual Circuit Routing
Primary destination
Vendor B
network
Secondary destination
A-3
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