A METHOD FOR TESTING A NETWORK ELEMENT IN A SYNCHRONOUS DIGITAL TELECOMMUNICATION SYSTEM

摘要

The invention relates to a method for testing the condition of a network element in a synchronous digital telecommunication system, such as the SDH or SONET system, which signal has a frame structure consisting of a predetermined number of bytes fixed in length and containing a pointer indicating the phase of payload within the frame structure. In order that the condition of the network element could be tested within the network element, a test byte (AUT, TUT) is inserted (105, 109) within the network element in at least one predetermined location in the frame structure, and said test byte is read (107, 111) within the network element at least at one monitoring point positioned after the insertion point.