Cell conformance testing in ATM networks

In this paper, we investigate how the concept of cell conformance testing, developed within the ITU-T for a single class of traffic could apply for connections with two types of traffic (namely with both CLP=0 and CLP=1 cells). For this purpose, we consider the Traffic Contract currently specified in ITU-T Recommendation 1.371 (i.e., declaration of the peak cell rates of the CLP=0 and the aggregate CLP=0+1 cell streams). To simplify the discussion and to be consistent with the current trend within the standardization bodies, we consider only connections for which cell loss rate objectives have to be guaranteed for both CLP=0 and CLP=1 traffic. All cell conformance testing procedures which may be envisaged for this Traffic Contract are examined and we show that most of them suffer from an undesirable phenomenon, namely measurement phasing, which jeopardizes their use. It turns out that only one procedure can be implemented for unambiguously testing cell conformance.