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Chapter 11
Circuits and Tunnels
Figure 11-9
Primary source
Vendor A
Secondary source
Several rules apply to secondary sources and destinations:
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•
•
•
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 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 path protection 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 path protection drop-and-continue connection is created at the source node.
11.16 Manual Circuit Routing
Routing circuits manually allows you to:
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•
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CTC imposes the following rules on manual routes:
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78-18106-01
Secondary Sources and Destinations
network
CTC does not allow a secondary destination for unidirectional circuits because you can always
specify additional destinations after you create the circuit.
The sources and destinations cannot be DS-3, DS3XM, or DS-1-based STS-1s or VT1.5s.
Secondary sources and destinations are permitted only for regular STS/VT1.5 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 destinations.
Choose a specific path, not necessarily the shortest path.
Choose a specific STS/VT1.5 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 path protection
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.
If you enabled Fully Path Protected, choose a diverse protect (alternate) path for every unprotected
segment
(Figure
11-10).
ONS 15454 network
Cisco ONS 15454 Reference Manual, R8.5
11.16 Manual Circuit Routing
Primary destination
Vendor B
network
Secondary destination
11-29
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