8135553
Highly secure and efficient routing
In this paper, we consider the problem of routing in an adversarial environment, where a sophisticated adversary has penetrated arbitrary parts of the routing infrastructure and attempts to disrupt routing. We present protocols that are able to route packets as long as at least one nonfaulty path exists between the source and the destination. These protocols have low communication overhead, low processing requirements, low incremental cost, and fast fault detection. We also present extensions to the protocols that penalize adversarial routers by blocking their traffic.
5165465
Adaptive control for packet video
Describes a portable and robust software mechanism for adaptive frame rate control for real time packet video transfer and viewing in workstation environments. No special hardware or system support is assumed. It includes (1) a responsive feedback system for dynamic presentation layer rate control in response to network load, (2) a simple and effective transport layer flow control scheme built upon an unreliable network protocol, and (3) data structures and scheduling support for integrating the rate and flow control mechanisms. The authors demonstrate that excellent jitter control is achieved by gracefully trading image resolution, and loss rates can be drastically reduced by appropriate flow control.<<ETX>>
14669009
Considering the energy consumption of mobile storage alternatives
This paper is motivated by a simple question: what are the energy consumption characteristics of mobile storage alternatives? To answer this question, we are faced with a design space of multiple dimensions. Two important dimensions are the type of storage technologies and the type of file systems. In this paper, we explore some options along each of these two dimensions. We have constructed a logical-disk system, which can be configured to run on different storage technologies and to emulate the behavior of different file systems. As we explore these configuration options, we find that the energy behavior is determined by a complex interaction of three factors: the power management mechanism of the storage device, the distribution of idleness in the workload, and the file system strategies that attempt to exploit and bridge these first two factors.
6622555
A quantitative analysis of cache policies for scalable network file systems
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.
In this paper, we investigate the quantitative performance effect of moving as many of the server responsibilities as possible to client workstations to reduce the need for high-performance server machines. We have devised a cache protocol in which all data reside on clients and all data transfers proceed directly from client to client. The server is used only to coordinate these data transfers. This protocol is being incorporated as part of our experimental file system, xFS. We present results from a trace-driven simulation study of the protocol using traces from a 237 client NFS installation. We find that the xFS protocol reduces server load by more than a factor of six compared to AFS without significantly affecting response time or file availability.
208003557
Serverless network file systems
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.
11858758
Improving the performance of log-structured file systems with adaptive methods
File system designers today face a dilemma. A log-structured file system (LFS) can offer superior performance for many common workloads such as those with frequent small writes, read traffic that is predominantly absorbed by the cache, and sufficient idle time to clean the log. However, an LFS has poor performance for other workloads, such as random updates to a full disk with little idle time to clean. In this paper, we show how adaptive algorithms can be used to enable LFS to provide high performance across a wider range of workloads. First, we show how to improve LFS write performance in three ways: by choosing the segment size to match disk and workload characteristics, by modifying the LFS cleaning policy to adapt to changes in disk utilization, and by using cached data to lower cleaning costs. Second, we show how to improve LFS read performance by reorganizing data to match read patterns. Using trace-driven simulations on a combination of synthetic and measured workloads, we demonstrate that these extensions to LFS can significantly improve its performance.
4989255
Face Detection Based on the Manifold
Data collection for both training and testing a classifier is a tedious but essential step towards face detection and recognition. It is a piece of cake to collect more than hundreds of thousands of examples from web and digital camera nowadays. How to train a face detector based on the collected immense face database? This paper presents a manifold-based method to select a training set. That is to say we learn the manifold from the collected enormous face database and then subsample and interweave the training set by the estimated geodesic distance in the low-dimensional manifold embedding. By the resulting training set, we train an AdaBoost-based face detector. The trained detector is tested on the MIT+CMU frontal face test set. The experimental results show that the proposed method based on the manifold is efficient to train a classifier confronted with the huge database.
5002092
How to Train a Classifier Based on the Huge Face Database?
The development of web and digital camera nowadays has made it easier to collect more than hundreds of thousands of examples. How to train a face detector based on the collected enormous face database? This paper presents a manifold-based method to subsample. That is, we learn the manifold from the collected face database and then subsample training set by the estimated geodesic distance which is calculated during the manifold learning. Using the subsampled training set based on the manifold, we train an AdaBoost-based face detector. The trained detector is tested on the MIT+CMU frontal face test set. The experimental results show that the proposed method is effective and efficient to train a classifier confronted with the huge database.
2587881
Isomap Based on the Image Euclidean Distance
Scientists find that the human perception is based on the similarity on the manifold of data set. Isometric feature mapping (isomap) is one of the representative techniques of manifold. It is intuitive, well understood and produces reasonable mapping results. However, if the input data for manifold learning are corrupted with noises, the isomap algorithm is topologically unstable. In this paper, we present an improved manifold learning method when the input data are images - the image Euclidean distance based isomap (imisomap), in which we use a new distance for images called image Euclidean distance (IMED). Experimental results demonstrate a consistent performance improvement of the algorithm imisomap over the traditional isomap based on Euclidean distance
36876991
Cooperative dynamics coordinated by stochastic noise in a multi-cell system
We investigate a general coupled noisy system with time delays for cooperative behavior in a multi-cell system. The main conclusion is that appropriate noise intensity and coupling are capable of driving the coupled system to synchrony or resonance, which may be exploited by biological organisms actively to facilitate mutual communication. A multi-cell system with a synthetic gene network, which consists of both intracellular and extracellular noise and time delays, is adopted to demonstrate the effect of noise and coupling on collective dynamics.
5657372
A Probabilistic Model for Recovering Camera Translation
This paper describes the mathematical basis and application of a probabilistic model for recovering the direction of camera translation (heading) from optical flow. According to the theorem that heading cannot lie between two converging points in a stationary environment, one can compute the posterior probability distribution of heading across the image and choose the heading with maximum a posteriori (MAP). The model requires very simple computation, provides confidence level of the judgments, applies to both linear and curved trajectories, functions in the presence of camera rotations, and exhibited high accuracy up to 0.1°?0.2° in random dot simulations.