Gojko Babic

Performance testing effort at the ATM Forum: an overview

The Test Working Group of the ATM Forum is developing a specification for performance testing of ATM switches and networks. The emphasis is on the user-perceived frame-level performance. This article explains what is different about this new effort and describes its status.

Experience with ATM switch performance testing

For users to be able to compare performance of different switches, it is important to have a common set of metrics. Examples of several such metrics and their measurements are presented in this paper. These measurements and metrics have impacted standardization efforts in this area. The key distinguishing feature of our effort is its emphasis on frame-level metrics (rather than cell-level metrics of the past). In particular, in this paper, we present definitions, methodologies, and measured results for frame latency, throughput, and maximum frame burst size (MFBS).

Methodology for implementing scalable test configurations in ATM switches

In performance testing of ATM switches and networks of switches a variety of connection configurations is needed. In most of the cases, these configurations require one traffic generator and/or analyzer for each switch port. Since this equipment is rather expensive, it is desirable to define scalable configurations that can be used with a limited number of generators. In this paper we present a methodology for the implementation of scalable connection configurations. The methodology is simple and offers a general solution to generate scalable connection configurations. Several examples of scalable configurations illustrate the methodology. The application of this methodology helps users to repeat easily performance tests under the same traffic load conditions.

Applicability of MIMO as metric for frame latency

ATM frame latency is one of the main QoS parameters and consequently an important target in performance testing. We compare MIMO (message in message out), a new metric for measuring frame latency, versus other metrics and in particular versus LCD (last cell delay). Analysis of examples as well as measurement results demonstrate that MIMO is less affected by test workload and is a better indicator of the switch performance, in particular for out-of-service testing. We show how to aggregate MIMO for a network of switches. The expression of MIMO aggregation clearly indicates the contribution of each network element and their interconnections to the total frame latency.

Measurement of ATM frame latency

Frame latency, as one of the main QoS parameters, quantifies also the level of quality of network devices. We proposed a new metric for ATM frame latency called MIMO (message-in message-out) latency that improves upon other latency metrics commonly used for continuous frame technologies. Analysis of examples and measurement results showed that MIMO is less workload dependent and a better indicator of switch performance. MIMO can be used to measure the frame latency of a single switch or of a network of switches. We showed that the formulation of MIMO aggregation is very useful in understanding the contribution of each network element and their interconnections to the total frame latency.