There is considerable interest in herbal therapies for cancer prevention but often with little sc... more There is considerable interest in herbal therapies for cancer prevention but often with little scientific evidence to support their use. In this study, we examined epidemiological data regarding effects of commonly used herbal supplements on risk for ovarian cancer and sought supporting ...
Delay-tolerant networks (DTNs) have the potential to interconnect devices in regions that current... more 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, intermittentlyconnected 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 time for each potential next hop. This learned topology information is distributed using a link-state routing protocol, where the link-state packets are "flooded" using epidemic routing. The routing is recomputed each time connections are established, allowing messages to take advantage of unpredictable contacts. A message is forwarded if the topology suggests that the connected node is "closer" to the destination than the current node.
There has been much debate over the past few years about the practice of moving traditional user-... more There has been much debate over the past few years about the practice of moving traditional user-space applications, such as web servers, into the kernel for better performance. Recently, the user-space ¤ server web server has shown promising performance for delivering static content. In this paper we first describe how we augmented the ¤ server to enable it to serve dynamic content. We then evaluate the performance of the ¤ server and the kernelspace TUX web server, using the SPECweb99 workload generator under a variety of static and dynamic workloads. We demonstrate that the gap in the performance of the two servers becomes less significant as the proportion of dynamic-content requests increases. In fact, for workloads with a majority of dynamic requests, the ¤ server outperforms TUX. We conclude that a well-designed user-space web server can compete with an in-kernel server on performance, while retaining the reliability and security benefits that come from operating in user space. The results presented in this paper will help system developers and administrators in choosing between the in-kernel and the user-space approach for web servers.
Delay-tolerant networks (DTNs) have the potential to connect devices and areas of the world that ... more Delay-tolerant networks (DTNs) have the potential to connect devices and areas of the world that are under-served by current networks. A critical challenge for DTNs is determining routes through the network without ever having an end-to-end connection, or even knowing which "routers" will be connected at any given time. Prior approaches have focused either on epidemic message replication or on knowledge of the connectivity schedule. The epidemic approach of replicating messages to all nodes is expensive and does not appear to scale well with increasing load. It can, however, operate without any prior network configuration. The alternatives, by requiring a priori connectivity knowledge, appear infeasible for a self-configuring network.
There is considerable interest in herbal therapies for cancer prevention but often with little sc... more There is considerable interest in herbal therapies for cancer prevention but often with little scientific evidence to support their use. In this study, we examined epidemiological data regarding effects of commonly used herbal supplements on risk for ovarian cancer and sought supporting ...
Delay-tolerant networks (DTNs) have the potential to interconnect devices in regions that current... more 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, intermittentlyconnected 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 time for each potential next hop. This learned topology information is distributed using a link-state routing protocol, where the link-state packets are "flooded" using epidemic routing. The routing is recomputed each time connections are established, allowing messages to take advantage of unpredictable contacts. A message is forwarded if the topology suggests that the connected node is "closer" to the destination than the current node.
There has been much debate over the past few years about the practice of moving traditional user-... more There has been much debate over the past few years about the practice of moving traditional user-space applications, such as web servers, into the kernel for better performance. Recently, the user-space ¤ server web server has shown promising performance for delivering static content. In this paper we first describe how we augmented the ¤ server to enable it to serve dynamic content. We then evaluate the performance of the ¤ server and the kernelspace TUX web server, using the SPECweb99 workload generator under a variety of static and dynamic workloads. We demonstrate that the gap in the performance of the two servers becomes less significant as the proportion of dynamic-content requests increases. In fact, for workloads with a majority of dynamic requests, the ¤ server outperforms TUX. We conclude that a well-designed user-space web server can compete with an in-kernel server on performance, while retaining the reliability and security benefits that come from operating in user space. The results presented in this paper will help system developers and administrators in choosing between the in-kernel and the user-space approach for web servers.
Delay-tolerant networks (DTNs) have the potential to connect devices and areas of the world that ... more Delay-tolerant networks (DTNs) have the potential to connect devices and areas of the world that are under-served by current networks. A critical challenge for DTNs is determining routes through the network without ever having an end-to-end connection, or even knowing which "routers" will be connected at any given time. Prior approaches have focused either on epidemic message replication or on knowledge of the connectivity schedule. The epidemic approach of replicating messages to all nodes is expensive and does not appear to scale well with increasing load. It can, however, operate without any prior network configuration. The alternatives, by requiring a priori connectivity knowledge, appear infeasible for a self-configuring network.
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