A-3
Cisco ONS 15454 Installation and Operations Guide
November 2001
AppendixA Circuit Routing
Manual Circuit Routing
FigureA-2 Secondary sources and drops
Several rules apply to secondary sources and drops:
•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
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 Fu lly 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 fr om the ON S 1 545 4 n etw ork t o the tw o
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:
•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
CTC imposes the following rules on manual routes:
•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 FigureA-1).
55402
Primary source
Secondary source
Primary destination
Secondary destination
Vendor A
network Vendor B
network
ONS 15454 network