Introduction

DAS is a wide-area distributed computer consisting of 200 Pentium Pro nodes. The machine is built out of clusters of workstations, located at the following Dutch universities:

• Vrije Universiteit, Amsterdam.
• University of Amsterdam.
• Delft University of Technology.
• Leiden University.

The clusters are interconnected by ATM links for wide-area, whereas Myrinet, a Gigabit LAN, is used for local communication.

In this report we will concentrate upon the WAN ATM links, however, their performance will also be compared with the ``normal'' Internet route. Distributed applications need relative short roundtrip times between the clusters to run effectively; the precise figures are application dependent. The available bandwidth is for distributed applications in general less important. The characteristics of the ATM connections in principle match well with these requirements.

To compare the capacity of the ATM route between the clusters with the ``normal'' Internet route a network monitor package called RTPL ( Remote Throughput, Ping and Load) is used. It is developed at the Institute of Computational Physics on the University of Utrecht. The purpose of this package is to obtain the network performance from an end user viewpoint. Therefore, some basic aspects of the network performance are measured by this script by using standard, general available software. The package uses dedicated scripts to invoke the net performance software. These scripts are also responsible for the sampling and storage of the results. The presentation of the results is a separate part. It is Web based and dynamic: the user can select various views at the data.

This report is organized as follows. Section 2 gives a more detailed description of this package. In section 3 the settings, used in the DAS monitor are described. The measurements are presented in section 4. In section 5 some end conclusions are given.