Making high-bandwidth Internet access pervasively available to a large worldwide audience is a difficult challenge, especially in many developing regions. As we wait for the uncertain takeoff of technologies that promise to improve the situation, we propose to explore an approach that is potentially more easily realizable: the use of digital storage media transported by the postal system as a general digital communication mechanism. We shall call such a system a Postmanet . Compared to more conventional wide-area connectivity options, the Postmanet has several important advantages, including wide global reach, great bandwidth potential, low cost, and ease of incremental adoption. While the idea of sending digital content via the postal system is not a new one, none of the existing attempts have turned the postal system into a generic and transparent communication channel that not only can cater to a wide array of applications, but also effectively manage the many idiosyncrasies associated with using the postal system. In the proposed Postmanet, we see two recurring themes at many different levels of the system. One is the simultaneous exploitation of the Internet and the postal system so we can combine their latency and bandwidth advantages. The other is the exploitation of the abundant capacity and bandwidth of the Postmanet to improve its latency, cost, and reliability.

The phenomenon that rural residents and people with low incomes lag behind in Internet access is known as the "digital divide." This problem is particularly acute in developing countries, where most of the world's population lives. Bridging this digital divide, especially by attempting to increase the accessibility of broadband connectivity, can be challenging. The improvement of wide-area connectivity is constrained by factors such as how quickly we can dig ditches to bury fibers in the ground; and the cost of furnishing "last-mile" wiring can be prohibitively high.In this paper, we explore the use of digital storage media transported by the postal system as a general digital communication mechanism. While some companies have used the postal system to deliver software and movies, none of them has turned the postal system into a truly generic digital communication medium supporting a wide variety of applications. We call such a generic system a Postmanet. Compared to traditional wide-area connectivity options, the Postmanet has several important advantages, including wide global reach, great bandwidth potential and low cost.Manually preparing mobile storage devices for shipment may appear deceptively simple, but with many applications, communicating parties and messages, manual management becomes infeasible, and systems support at several levels becomes necessary. We explore the simultaneous exploitation of the Internet and the Postmanet, so we can combine their latency and bandwidth advantages to enable sophisticated bandwidth-intensive applications.

This paper describes and evaluates a probabilistic packet scheduling (PPS) algorithm for providing different levels of service to TCP flows. With our approach, each router defines a local currency in terms of tickets and assigns tickets to its inputs based on contractual agreements with its upstream routers. A flow is tagged with tickets to represent the relative share of bandwidth it should receive at each link. When multiple flows share the same bottleneck, the bandwidth that each flow obtains is proportional to the relative tickets assigned to that flow. Simulations show that PPS does a better job of proportionally allocating bandwidth than DiffServ and weighted CSFQ. In addition, PPS accommodates flows that cross multiple currency domains.

In this paper, we study how to minimize the latency of a message through a network that consists of a number of store-and-forward stages. This research is especially relevant for today's low overhead communication systems that employ dedicated processing elements for protocol processing. We develop an abstract pipeline model that reveals a crucial performance tradeoff involving the effects of the overhead of the bottleneck stage and the bandwidth of the remaining stages. We exploit this tradeoff to develop a suite of fragmentation algorithms designed to minimize message latency. We also provide an experimental methodology that enables the construction of customized pipeline algorithms that can adapt to the specific system characteristics and application workloads. By applying this methodology to the Myrinet-GAM system, we have improved its latency by up to 51%. Our theoretical framework is also applicable to pipelined systems beyond the context of high speed networks.

Article Free Access Share on Improving the performance of log-structured file systems with adaptive methods Authors: Jeanna Neefe Matthews Computer Science Division, University of California, Berkeley Computer Science Division, University of California, BerkeleyView Profile , Drew Roselli Computer Science Division, University of California, Berkeley Computer Science Division, University of California, BerkeleyView Profile , Adam M. Costello Computer Science Division, University of California, Berkeley Computer Science Division, University of California, BerkeleyView Profile , Randolph Y. Wang Computer Science Division, University of California, Berkeley Computer Science Division, University of California, BerkeleyView Profile , Thomas E. Anderson Computer Science Division, University of California, Berkeley Computer Science Division, University of California, BerkeleyView Profile Authors Info & Claims SOSP '97: Proceedings of the sixteenth ACM symposium on Operating systems principlesOctober 1997Pages 238–251https://doi.org/10.1145/268998.266700Published:01 October 1997Publication History 102citation1,857DownloadsMetricsTotal Citations102Total Downloads1,857Last 12 Months115Last 6 weeks19 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Publisher SiteeReaderPDF

Large-scale parallel machines are incorporating increasingly sophisticated architectural support for user-level messaging and global memory access. We provide a systematic evaluation of a broad spectrum of current design alternatives based on our implementations of a global address language on the Thinking Machines CM-5, Intel Paragon, Meiko CS-2, Cray T3D, and Berkeley NOW. This evaluation includes a range of compilation strategies that make varying use of the network processor; each is optimized for the target architecture and the particular strategy. We analyze a family of interacting issues that determine the performance trade-offs in each implementation, quantify the resulting latency, overhead, and bandwidth of the global access operations, and demonstrate the effects on application performance.

We propose a new paradigm for network file system design:serverless network file systems. While traditional network file systems rely on a central server machine, a serverless system utilizes workstations cooperating as peers to provide all file system services. Any machine in the system can store, cache, or control any block of data. Our approach uses this location independence, in combination with fast local area networks, to provide better performance and scalability than traditional file systems. Furthermore, because any machine in the system can assume the responsibilities of a failed component, our serverless design also provides high availability via redundatn data storage. To demonstrate our approach, we have implemented a prototype serverless network file system called xFS. Preliminary performance measurements suggest that our architecture achieves its goal of scalability. For instance, in a 32-node xFS system with 32 active clients, each client receives nearly as much read or write throughput as it would see if it were the only active client.

Article Serverless network file systems Share on Authors: T. E. Anderson Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile , M. D. Dahlin Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile , J. M. Neefe Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile , D. A. Patterson Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile , D. S. Roselli Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile , R. Y. Wang Computer Science Division, University of California at Berkeley Computer Science Division, University of California at BerkeleyView Profile Authors Info & Claims SOSP '95: Proceedings of the fifteenth ACM symposium on Operating systems principlesDecember 1995 Pages 109–126https://doi.org/10.1145/224056.224066Online:03 December 1995Publication History 255citation3,156DownloadsMetricsTotal Citations255Total Downloads3,156Last 12 Months71Last 6 weeks6 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Current network file system protocols rely heavily on a central server to coordinate file activity among client workstations. This central server can become a bottleneck that limits scalability for environments with large numbers of clients. In central server systems such as NFS and AFS, all client writes, cache misses, and coherence messages are handled by the server. To keep up with this workload, expensive server machines are needed, configured with high-performance CPUs, memory systems, and I/O channels. Since the server stores all data, it must be physically capable of connecting to many disks. This reliance on a central server also makes current systems inappropriate for wide area network use where the network bandwidth to the server may be limited.