CONTENTS

 1     Introduction
        1.1     Purpose
        1.2     Scope
 2     References
 3     Abbreviations
 4     Definition of paths, path elements and path element categories
        4.1     Path
        4.2     Path element
        4.3     Path element categories
                  4.3.1     Network location
                  4.3.2     Length
                  4.3.3     Performance level
 5     Definition of parameters
        5.1     General
        5.2     Availability ratio
        5.3     Mean time between digital path outages
 6     Availability performance objectives
        6.1     Path elements operating at the primary rate
                  6.1.1     Availability ratio
                  6.1.2     Mean time between digital path outages
        6.2     Path elements operating at bit rates above the primary rate
Annex A – Examples of path topologies and end-to-end availability performance derivations
        A.1     Purpose
        A.2     Path topologies
        A.3     End-to-end unavailability
                  A.3.1     Linear topology
                  A.3.2     Redundant topology
        A.4     End-to-end outage intensity
                  A.4.1     Linear topology
                  A.4.2     Redundant topology
        A.5     Numerical examples
Annex B – Methods for measuring availability performance of path elements
        B.1     Purpose
        B.2     Measurement methods
        B.3     Sampling estimation procedure