The test equipment specified in this Recommendation consists principally of a jitter/wander measurement function and a jitter/wander generation function. Measurements can be performed at the physical layer of synchronous Ethernet systems. A bit error rate test set may be part of the same equipment or may be physically separate. [ITU-T O.172] specifies the test equipment for generation and measurement of jitter and wander in digital systems based on the synchronous digital hierarchy (SDH). [ITU-T G.8261]@ [ITU-T G.8262] and [ITU-T G.8264] should be read in conjunction with this Recommendation.