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Self-adaptive and self-organizing systems must be self-monitoring. Recent research has shown that self-monitoring can be enabled by using correlations between monitoring variables (metrics). However, computer systems often make a very large number of metrics available for collection. Collecting them all not only reduces system performance, but also creates other overheads related to communication,...
Modern software systems expose management metrics to help track their health. Recently, it was demonstrated that correlations among these metrics allow faults to be detected and their causes localized. In particular, linear regression models have been used to capture metric correlations. We show that for many pairs of correlated metrics in software systems, such as those based on Java Enterprise Edition...
Management metrics of complex software systems exhibit stable correlations which can enable fault detection and diagnosis. Current approaches use specific analytic forms, typically linear, for modeling correlations. In this paper we use normalized mutual information as a similarity measure to identify clusters of correlated metrics, without knowing the specific form. We show how we can apply the Wilcoxon...
A correctly functioning enterprise-software system exhibits long-term, stable correlations between many of its monitoring metrics. Some of these correlations no longer hold when there is an error in the system, potentially enabling error detection and fault diagnosis. However, existing approaches are inefficient, requiring a large number of metrics to be monitored and ignoring the relative discriminative...
In infrastructure wireless networks, nodes at the edge of the coverage area need to spend more energy to transmit their packets than those close to the Access Point (AP). Less energy is required if intermediate nodes can be used to forward data. To enable this, intermediate nodes need an incentive and there must be a mechanism for selecting these nodes. In this paper we propose Energy-aware Co-Operative...
The use of 802.11-based multi-hop wireless mesh networks for Internet access is extensive and growing. The primary advantages of this approach are ease of deployment and lower cost. However, these networks are designed for web and e-mail applications. Highly interactive applications, such as multiplayer online games and VoIP, with their requirements for low delay, present significant challenges to...
Autonomic systems require continuous self-monitoring to ensure correct operation. Available monitoring data exists in a variety of formats, including log files, performance counters, traces, and state and configuration parameters. Such heterogeneity, together with the extremely large volume of data that could be collected, makes analysis very complex. To allow for more-effective problem determination,...
The use of multi-hop wireless networks based on 802.11 technology is extensive and growing, owing to their ease of deployment and low cost. However, such networks exhibit poor fairness, starving nodes that are too many hops distant from the gateway. The best current solution to this problem is source rate limiting. While effective in many topologies, this fails to completely address the fairness problem...
Computing and communication are in flux today. On the communication side, historically there have been multiple, parallel networks servicing different types of traffic. Cost pressures are forcing convergence to a single IP-based network. Simultaneously the computing world has been steadily moving from monolithic applications to client/server systems, and from there to arbitrary distributed applications...
Gateway nodes in a wireless mesh network (WMN) bridge traffic between the mesh nodes and the public Internet. This makes them a suitable aggregation point for policy enforcement or other traffic-shaping responsibilities that may be required to support a scalable, functional mesh network. In this paper we evaluate two gateway-enforced rate-limiting mechanisms so as to avoid congestion and support network-level...
Delay-tolerant networks (DTNs) have the potential to interconnect devices in regions that current networking technology cannot reach. To realize the DTN vision, routes must be found over multiple unreliable, intermittently-connected hops. In this paper we present a practical routing protocol that uses only observed information about the network. We designed a metric that estimates the average waiting...
In this tutorial wireless mesh networks (WMNs) is discussed, which has the routing protocols of actual capacity. The multi-radio systems, technical problems are also described in this issue, such that the WMN have significant congestion control and fairness problems
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