March 1987 | NTIA Technical Report TR-87-214
Abstract: The objective of this study is to look at fiber optics networks in a predominately functional domain and to assess their potential survivability advantages from that point of view. As a consequence, service survivability is emphasized far more than physical survivability, although physical existence of facilities is a definite prerequisite for all telecommunications services. The need for a quantitative (or formal, or unique, or numerical) definition of the term "survivability" is addressed. The report proposes a partial solution to this problem. It introduces a network–related quantity, defined with the moments of the connectivity cross section histograms, that appears to possess many of the properties wanted for measuring and comparing survivability of different topologies. For lack of a better name, that quantity may be called the effective topological survivability index. The fiber advantage of large data throughput, typically in tens of Mb/s, must be exploited when connectivity or other network status is in doubt. This is part of the network reconstitution or restoration issue. Outlines of procedures, protocols, and formats are given to achieve comprehensive network–wide restoral for small but still realistic networks. The information fields of extensive reconstitution data arrays are possible and advisable. If transmitted, received, and stored rapidly, and not processed in a lengthy manner, these data arrays are shown to offer unprecedented restoral opportunities. Through locally or regionally focused restoration processes the methods appear practicable even for very large networks. The conclusion is that full–scale automation is essential. It should be distributed to all nodes of the network and its implementation should be with the very highest speed parallel processors. Any node that survives should be capable of both initiating and participating in the network restoration sessions. Thus, centralized hierarchical controls are to be avoided.
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