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I. Introduction

This work has been done in the framework of High and Low Energy Physics applications (real-time trigger and event building), in which we are concerned in the installation of standard commercial processing nodes interconnected by Fibre Channel communications and switching equipment. High Energy Physics applications need a real-time computing network whose major challenge is exchange of short messages with very low latency, coupled with high performance processors. On the contrary, the new generation of Low Energy Physics experiment has not a critical timing, since the trigger scheme is usually performed by dedicated hardware devices, but needs performant switching capabilities and high bandwidth. These applications are described in paragraphs II and III.

The aim of this work was to measure communication performances at the user level when exchanging data between IBM workstations via an eight port IBM Fibre Channel Fabric (or switch). Similar tests have already been performed at CERN with different kinds of equipment on heterogeneous systems (IBM and HP workstations with different power, ANCOR and IBM Fibre Channel interfaces, ANCOR Fibre Channel Fabric) with different kernel configuration [1], [2], [3] and [4].

Thanks to IBM-ECSEC at Rome, the test with the following homogeneous hardware configuration has been made feasible:

The six workstations were RS/6000-560 machines with a POWER architecture running at 50 Mhz. The IBM Fibre Channel interfaces to the MCA bus (RS/6000 IBM workstation) are 32 bit bus Master capable of data transfer rates up to 40 MBytes/s: they do not represent a bottleneck in the system, where the speed of each 50 micron optic fibre is 266 Mbits/s. The Fibre Channel equipment is implementing version 4.3.

The commercial driver available from IBM [5] for the Fibre Channel adapters offers two different API (Application Programming Interface):

We performed transmission tests using both APIs and results are reported hereinafter.

RD11 - 22 JUN 95
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