Networking automatic test equipment environments

Automatic test equipment (ATE) is a term that, in its broadest meaning, indicates a generic system capable of performing measurements in an automatic or semiautomated (human-assisted) way. Years ago, this term was used specifically to refer to an automated measurement system employed to test the functionality of some electronic device-under-test (DUT). Typical applications were in the manufacturing area, where ATE had a twofold nature: in-circuit testing and functional testing. For in-circuit testing, ATE often were stand-alone complex programmable machines, equipped with a bed-of-nails adapter specifically designed as a fixture to provide signal inputs and meaningful test-points of the DUT. The test engineer had the responsibility of writing code that determined the exact sequence of stimulus signals, response measurements, and go/no-go decisions. For this aim, a switch matrix and the ATE itself were suitably controlled and coordinated by a workstation. For functional testing, ATE consisted of off-the-shelf instruments connected to the DUT by some kind of front-end adapter. In the latter case, most of the effort of the test engineer consisted of designing a program to control the various instruments to assess DUT performances. When planning the use of a dedicated testing machine as opposed to a test bench, other factors were taken into account: measurement speed, cost, and fault coverage.     

Internet Traffic Measurement: A Critical Study of Wavelet Analysis

In communication networks, traffic measurements serve two main purposes: the characterization of traffic-load patterns and the monitoring of performances. This paper is a study of the applicability of traffic-analysis methods as a means of detecting malfunctions and performance changes in packet data networks through measurements of selected parameters. The main contribution is of a methodological nature and is motivated by the fact that wavelet analysis, which has come to be regarded as a standard approach, is by no means a straightforward method. Controversial results can be found that are not always attributable to the complex nature of the measured object. Careful study of the uncertainty of traffic-parameter estimates is also an important issue, which turns out to be somewhat neglected in the literature. The aim of this paper is twofold: on the one hand, to enhance the model validation process and, on the other hand, to provide for objective assessment of the feasibility of network-monitoring procedures that rely on measurement and model-based diagnostics     

On the Analysis of Communication and Computer Networks by Traffic Flow Measurements

This paper investigates the potential contributions of traffic flow measurements in monitoring and network diagnostics. The basic idea is that information of diagnostic relevance may be obtained from the detection of local anomalies in a traffic trace. For this purpose, this paper introduces a novel approach in the analysis of aggregate traffic, based on the determination of empirical rate-interval curves (RICs). These curves allow an analysis of flow quantiles versus time scale, which is helpful both in the investigation of the scaling properties of network traffic and in diagnostics. RIC-based analyses of traffic measurements taken from different networks are presented and show that the proposed approach appears to be effective in evidencing potential flow anomalies.     

Passive measurement tool for monitoring mobile packet network performances

Continuous monitoring of performances is necessary to detect critical situations in the radio interface of digital mobile telephone networks. This paper presents a measurement tool that analyzes Transmission Control-Protocol (TCP) level packet traffic and detects the effects of variations in the radio-channel conditions of a wireless network. The analysis algorithm considers the wavelet coefficients of the aggregated-traffic process at a suitably selected number of time scales. Variations in the energy of wavelet coefficients are detected by a statistical test, from which a score is calculated. This indicator reveals changes in the performances of the monitored network.     

Euler characteristics of oceanic sea states

We present an application of a novel Variational Wave Acquisition Stereo System (VWASS) for the estimation of the wave surface height of oceanic sea states. Specifically, we show that VWASS video technology combined with statistical techniques based on Euler Characteristics of random fields provides a new paradigm for the prediction of wave extremes expected over a given area of the ocean.     

Statistical analysis of measurements for telecommunication-network troubleshooting

This paper presents a method for assessing network failures by means of a suitable statistical post-processing analysis of measurement data collected by nonintrusive devices. The proposed solution can be easily implemented by already available monitoring instruments for network performance surveillance and automatic detection of anomalies. The effectiveness of the method has been proven on real-life telecommunication systems, and results are reported.