ABSTRACT: This GR provides criteria necessary for Network Elements (NEs) to support Layer 1 surveillance of digital transmission systems and signals. It includes both criteria that are specific to NEs that terminate or transport DS1 and/or DS3 signals, and common criteria that are applicable to multiple types of NEs and are referenced by other technology-specific documents such as (in the case of SONET) GR-253.

This GR is expected to be of use to service providers, NE suppliers, and suppliers of Operations Systems (OSs) that support the collection and processing of surveillance information.

While the criteria are generally aligned with the specifications in several ATIS standards (i.e., ATIS-0300231, ATIS-0300231.02 and ATIS-0300231.03), this GR provides additional information and clarifications on a number of surveillance-related topics. In addition, it highlights various discrepancies within or between other documents.

Issue 3 contains:

• Rearrangement of the information and criteria in multiple sections of the document to improve its logical flow.
• Clarification of the distinction between performance parameters and non-performance parameters, both of which are subsets of the broader category of PM parameters
• Addition of information and criteria on various "common" topics, including the adjustment of registers upon entry into or exit from unavailable time, Threshold Crossing Alert (TCA) generation, Intermediate PM (IPM) and invalid data flags
• Addition of information and criteria related to CI and network performance monitoring of DS3 paths
• Definition of "initial default" threshold values and "NE-specific default" threshold values, and the addition of corresponding criteria
• Revision of the information related to protection switching and the corresponding PM parameters
• Addition of information and criteria related to the possible suppression of TCAs for entities affected by declared failures
• Changes to eliminate redundancies (and thus potential discrepancies) with GR 499 CORE on subjects such as signal formats, defect detection and termination, and failure declaration and clearing, while also addressing certain aspects of several of those same topics which are not covered in the current issue of that GR.