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This paper presents a dependability study of high-speed, switched Local Area Networks (LANs) using Myrinet as an example testbed (with theoretical speeds of 2.56 Gbps). The study uses results of two fault injection methods, simulated fault injection and softwareimplemented fault injection (SWIFI), to analyze the application-level impact of transient faults injected into the network interface hardware. These results include a number of errors such as dropped or corrupt messages, host interface or host resets, and local or remote host interface hangs. The paper presents the study in two parts: First, the results from the SWIFI method in the real system are used as a basis to validate the simulation and identify the major factors leading to di erences between the methods. A comparison between the two injection methods shows that they agree for 83% of the fault injections. The results, however, vary greatly depending on the fault type considered. The study presents an analysis of the e ects of varying workload intensity, host platform, and interface function targeted by the injection. An example of this analysis is to show that the function targetted has a signi cant impact on the fault activation rate. Finally, the study identi es two mechanisms by which faults may propagate from the interface to other parts of the network; in one example, this propagation caused the interface's host computer to reboot while another caused a remote interface in the network to hang.

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Successful deployment of networked multimedia applications such as IP Telephony depends on the performance of the underlying data network. QoS requirements of these applications are different from those of traditional data applications. For example, while IP Telephony is very sensitive to delay and jitter, traditional data applications are more tolerant of these performance metria. Consequently, assessinganetwork todetermine whether it can accommodate the stringent QoS requirements oflF' Telephony becomes critical. In this paper we describe a technique for evaluating a network for IF' Telephony readiness. Our technique relies on the data collection and analysis support of our prototype tool, ExametW. It automatically discovers the topology of a given network and collects and integrates network device performance and voice quality metrics. We report the results of assessing the IF' Telephony readiness of a real network of 31 network devices (routedswitches) and 23 hosts via ExamiNetm. Our evaluation identified links in the network that were over utilized to the point at which they could not handle IF' Telephony.

This paper presents an injection-based approach to analyze dependability of high-speed networks using the Myrinet as a n example testbed. Instead of injecting faults related to network protocols, we injected faults into the host interface component, which performs the actual send and receive operations. The fault model used was a temporary single bit flip in an instruction executing o n the host interface's custom processor, corresponding to a transient fault in the processor itself. Results show that more than 25% of the injected faults resulted in interface failures. Furthermore, we observed fault propagation from a n interface to its host computer or to another interface to which it sent a message. These findings suggest that two important issues for high-speed networking in critical applications are protecting the host computer from errant or malicious interface components and implementing thorough message acceptance test mechanisms to prevent errant messages from propagating faults between interfaces.