A new network element for performance monitoring and test access spanning the digital hierarchy

A description is given of an integrated transport access unit (ITAU) that interfaces to the network at the DS3 rate and combines the capabilities of a conventional digital test access unit with those of an embedded monitoring unit that spans the digital hierarchy. The ITAU provides a remote gateway to an operations support system (OSS), facilitating the isolation and elimination of error conditions in the network. Since the ITAU is an in-line network element, it must maintain maximum transparency while performing tests on embedded channels in a hitless fashion so that all other channels pass through unaffected. Continuous performance monitoring at all levels of the hierarchy, combined with individual channel test access, allows the ITAU to act as a diagnostic pickup point in the network. Multiple ITAUs positioned throughout the network and connected through the OSS allow network faults to be detected and isolated quickly