Sharing digital content with others is now an important part of human social activities. Despite the increasing need to share, most sharing operations are not simple. Many applications are not interoperable with others, require an Internet connection, or require cumbersome configuration and coordination efforts. Our idea is to simplify digital content sharing on mobile devices by providing support for self-organizing heterogeneous networks and pervasive storage. That is, mobile devices can spontaneously connect to each other over a mixture of different available networks (e.g., 3G/4G, WiFi, Bluetooth, etc.) without requiring an explicit user action of network selection or mandatory Internet access. Moreover, indirect communication can be further augmented by pervasive storage. Mobile devices can store shared content on it, which can later be automatically downloaded by other devices in proximity, thus allowing location-based sharing with minimal coordination even when devices are not in the same location at the same time. This paper shows how these technologies can be incorporated into mobile content-sharing middleware to simplify sharing operations among mobile devices without any modification to commercially available devices or applications. In particular, (i) we provide an implementation of our approach as extension modules for existing content-sharing middleware, (ii) we present two example applications built on top of it, and (iii) we demonstrate our approach through experiments in representative situations.

ShAir is a middleware infrastructure that allows mobile applications to share resources of their devices (e.g., data, storage, connectivity, computation) in a transparent way. The goals of ShAir are: (i) abstracting the creation and maintenance of opportunistic delay-tolerant peer-to-peer networks; (ii) being decoupled from the actual hardware and network platform; (iii) extensibility in terms of supported hardware, protocols, and on the type of resources that can be shared; (iv) being capable of self-adapting at run-time; (v) enabling the development of applications that are easier to design, test, and simulate. In this paper we discuss the design, extensibility, and maintainability of the ShAir middleware, and how to use it as a platform for collaborative resource-sharing applications. Finally we show our experience in designing and testing a file-sharing application.

In this paper, “Martini,” a network interface controller chip for our original network called RHiNET is described. Martini is designed to provide high-bandwidth and low-latency communication with small overhead. To obtain high performance communication, protected user-level zero-copy RDMA communication functions are completely implemented by a hardwired logic. Also, to reduce the communication latency efficiently, we have proposed PIO-based communication mechanisms called “On-the-fly (OTF)” and have implemented them on Martini. The evaluation results show that Martini connected to a 64bit/66MHz PCI-bus achieves 470MByte/s maximum bidirectional bandwidth and 1.74 μsec minimum latency on host-to-host memory copying.

By recent performance improvement of interconnection networks for a PC cluster, standard I/O bus which connects network interface becomes the performance bottleneck. DIMMnet is a network interface which can solve the problem by using the memory bus instead of PCI bus or other I/O buses. The second generation network interface DIMMnet-2 can be connected with DDR-SDRAM slot by using the indirect accessing to memory and buffers. Although the current board is a prototype using an FPGA, the latency for 8 Bytes data transfer is only 0.441µs.

System area networks (SANs), which usually accept arbitrary topologies, have been used to connect nodes in PC/WS clusters or high-performance storage systems. Although deadlock-free routings, multicasts, and topologies for SANs have been widely developed, their evaluation on real PC clusters was rarely done. Thus, the evaluation of routings, multicasts, and topologies in real systems is important to analyze their impact on the total systems and validate their simulation results. In this paper, we implement and evaluate deadlock-free routings and unicast-based multicasts under various topologies and channel buffer sizes on a PC cluster called RHiNET-2 with 64 hosts. Execution results show that descending layers (DL) routing and structured channel pools improve up to 57 percent of bandwidth and 34 percent of barrier synchronization time compared with up*/down* routing. They also show that, by visiting hosts in numerical order, execution time of unicast-based barrier synchronization is improved up to 28 percent compared with that in random order. However, channel buffer sizes don't affect the bandwidth in the RHiNET-2 cluster. In addition to fundamental evaluation, we appraise them using NAS Parallel Benchmarks, and the DL routing achieves 3.2 percent improvement on their execution time compared with up*/down* routing.

RHiNET-2/NI is a network interface for a parallel and distributed computing system with network connected PCs. The core of the network interface is an ASIC network controller chip Martini, which provides low-latency and large-bandwidth communication. Evaluation results show that it achieves almost full bandwidth of the 66MHz/64bit PCI bus, which is much larger than that of Myrinet-2000. The performance of a small prototype parallel system achieves almost linear speed up.

System area networks (SANs), which usually accept irregular topologies, have been used to connect nodes in PC/WS clusters or high-performance storage systems. A lot of deadlock-free routings for SANs have been proposed, and their evaluation on simulations have been widely done. However, these simulation results may differ from that of real PC clusters, since hosts, network interfaces and switches used in the simulation are simplified for achieving enough simulation speed. In this paper, we implement deadlock-free routings on a high-performance PC cluster called RHiNET-2, and evaluate their performance. Execution results show that the DL routing and the structured channel pools achieve almost the same total bandwidth and execution time of the barrier synchronization. Compared with the simple Up*/Down* routing, they improve 51% of total bandwidth and 29% improvement on execution time of the barrier synchronization.

System area networks (SANs), which usually accept irregular topologies, have been used to connect nodes in PC/WS clusters or high-performance storage systems. Since wormhole or virtual cut-through transfer is used for low latency communication, deadlock-free routings are essential in SANs. We propose a novel deadlock-free deterministic routing called descending layers (DL) routing for SANs. In order to reduce both nonminimal paths and traffic congestion, the network is divided into layers of subnetworks with the same topology using virtual channels, and a large number of paths across multiple subnetworks are established. The DL routing is implemented on a real PC cluster called RHiNET-2, and execution results show that its throughput is improved up to 33% compared with that of up*/down* routing. Its execution time of a barrier synchronization is also improved 29% compared with that of up*/down* routing. Simulation results of various sizes and topologies also show that the DL routing achieves up to 266% improvement on throughput compared with up*/down* routing.