Optical Network Design and Planning
Oriented towards practical implementation, this guide takes a pragmatic approach to deploying state-of-the-art optical networking equipment in metro-core and backbone networks.
TABLE OF CONTENTS Optical Network Design and Planning
7.1: Dedicated vs. Shared Protection
7.1 Dedicated vs. Shared Protection
One of the basic dichotomies among protection schemes is whether the protection is dedicated or shared, This dichotomy exists with protection at any network layer, not just optical protection. For ease of discourse, this section compares dedicated and shared protection in relation to link/node failures (as opposed to, e.g., equipment failures). Furthermore, it assumes the protection mechanism is path-based, where recovery is provided by moving the connection to an alternative end-to-end path; however, the dedicated vs. shared paradigm applies to more general protection schemes. (Path-based protection is discussed further in Section 7.4, along with alternative schemes.)
7.1.1 Dedicated Protection
In dedicated protection, spare resources are specifically allocated for a particular demand. If a demand is brought down by a failure, it is guaranteed that there will be available resources to recover from the failure, assuming the backup resources have not failed also.
Dedicated protection generally falls into one of two categories. In 1+1 dedicated protection, the backup path is active ; i.e., there are two live connections between the source and destination, and the destination is equipped with decision circuitry to select the better of the two paths. In contrast, in 1:1 dedicated protection, the backup path does not become active until after a failure has occurred on the primary path. After the failure is repaired, the connection may return to the primary path (i.e., revertive mode) or may remain on the backup path (i.e., nonrevertive mode).
There are several advantages to operating dedicated...
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