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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
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Chapter 9 SDH Topologies and Upgrades
Subnetwork Connection Protection Configurations
Note If a Subnetwork Connection Protection circuit is created manually by TL1, DCCs are not needed.
Therefore, Subnetwork Connection Protection circuits are limited by the cross-connection bandwidth or
the span bandwidth, but not by the number of DCCs.
Because each traffic path is transported around the entire ring, Subnetwork Connection Protection
configurations are best suited for networks where traffic concentrates at one or two locations and is not
widely distributed. Subnetwork Connection Protection capacity is equal to its bit rate. Services can
originate and terminate on the same Subnetwork Connection Protection configuration, or they can be
passed to an adjacent access or interoffice ring for transport to the service-terminating location.
9.1.1 Subnetwork Connection Protection Bandwidth
The span bandwidth consumed by a Subnetwork Connection Protection circuit is two times the circuit
bandwidth, because the circuit is duplicated. The cross-connection bandwidth consumed by a
Subnetwork Connection Protection circuit is three times the circuit bandwidth at the source and
destination nodes only. For the ONS 15310-MA SDH, the spans can be STM1, STM4, or STM16.
9.1.2 Subnetwork Connection Protection Application Example
Figure 9-1 shows a basic Subnetwork Connection Protection configuration. If Node ID 0 sends a signal
to Node ID 2, the working signal travels on the working traffic path through Node ID 1. The same signal
is also sent on the protect traffic path through Node ID 3.
Figure 9-1 Basic Four-Node SNCP Ring
If a fiber break occurs (Figure 9-2), Node ID 2 switches its active receiver to the protect signal coming
through Node ID 3.
15310-MA SDH
Node ID 0
15310-MA SDH
Node ID 1
15310-MA SDH
Node ID 2
15310-MA SDH
Node ID 3
243022
= Fiber 1
= Fiber 2