No abstract

It is a challenge to provide detection facilities for large-scale distributed systems running legacy code on hosts that may not allow fault tolerant functions to execute on them. It is tempting to structure the detection in an observer system that is kept separate from the observed system of protocol entities, with the former only having access to the latter's external message exchanges. In this paper, we propose an autonomous self-checking Monitor system, which is used to provide fast detection to underlying network protocols. The Monitor architecture is application neutral and, therefore, lends itself to deployment for different protocols, with the rulebase against which the observed interactions are matched, making it specific to a protocol. To make the detection infrastructure scalable and dependable, we extend it to a hierarchical Monitor structure. The Monitor structure is made dynamic and reconfigurable by designing different interactions to cope with failures, load changes, or mobility. The latency of the Monitor system is evaluated under fault free conditions, while its coverage is evaluated under simulated error injections.

In this paper we present a data dissemination protocol for efficiently distributing data through a sensor network in the face of node and link failures. Our work is motivated by the SPIN protocol which uses metadata negotiation to minimize data transmissions. We propose a protocol called Shortest Path Minded SPIN (SPMS) in which every node has a zone defined by its maximum transmission radius. A node which is a data source advertises the availability of data to all the nodes in its zone using a metadata descriptor. Any interested node requests the data and gets sent the data using multi-hop communication via the shortest path. The failure of any node in the path is detected and recovered using backup routes. We build simulation models to compare SPMS against SPIN. Different scenarios including mobility and node failures are simulated. The simulation results show that SPMS reduces the delay over 10 times and consumes 30% less energy in the static failure free scenario. Even with the addition of mobility, SPMS outperforms SPIN by energy gains between 5% and 21%.An analytical model is also constructed to compare the two protocols under a simplified topology.

The wide deployment of high-speed computer networks has made distributed systems ubiquitous in today's connected world The machines on which the distributed applications are hosted are heterogeneous in nature, the applications often run legacy code without the availability of their source code, the systems are of very large scales, and often have soft real-time guarantees. In this paper, we target the problem of online detection of disruptions through a generic external entity called Monitor that is able to observe the exchanged messages between the protocol participants and deduce any ongoing disruption by matching against a rule base composed of combinatorial and temporal rules. The Monitor architecture is application neutral, with the rule base making it specific to a protocol. To make the detection infrastructure scalable and dependable, we extend it to a hierarchical Monitor structure. The infrastructure is applied to a streaming video application running on a reliable multicast protocol called TRAM installed on the campus wide network. The evaluation brings out the scalability of the Monitor infrastructure and detection coverage under different kinds of faults for the single level and the hierarchical arrangements.