ATIS 0900105.09 2013 Edition, April 1, 2013
Synchronous Optical Network (SONET) – Network Timing and Synchronization
This standard describes and specifies the minimum synchronization-related performance parameters for SONET network interfaces. These specifications apply to all electrical and optical SONET network interfaces as defined in ATIS-0900105, whereas ATIS-0900101 applies only to network interfaces for carrying synchronization between carriers.
Synchronization-related specifications for SONET network interfaces are necessary to achieve satisfactory performance at network interconnections. It is important to specify the synchronization performance limits at the network interfaces in terms of frequency offsets, frequency changes, and wander. Inadequate control of the synchronization performance of network interfaces can lead to excessive pointer adjustments, which can in turn lead to error bursts on payload signals due to jitter and/or slips caused by excessive wander. Wander of SONET signals must also be limited since it can be transferred onto the asynchronous payloads through the mapping mechanism.
Note that SONET NEs are not required to have an internal clock that meets the stratum level requirements as described in ATIS-0900101. This document defines the minimum performance specification for SONET signals at interfaces that are timed by SONET NEs with clocks that have free-run and holdover accuracies that are of lower quality than the stratum 3 level. Herein, these clocks are referred to as SONET minimum clocks (SMC). Some SONET NEs may be required, by either network operators or application, to support a minimum of stratum 3 level performance.