8295901
Bounded-latency content distribution feasibility and evaluation
This paper investigates the performance of a content distribution network designed to provide bounded content access latency. Content can be divided into multiple classes with different configurable per-class delay bounds. The network uses a simple distributed algorithm to dynamically select subsets of its proxy servers for different classes such that a global per-class delay bound is achieved on content access. The content distribution algorithm is implemented and tested on PlanetLab, a world-wide distributed Internet testbed. Evaluation results demonstrate that, despite Internet delay variability, subsecond delay bounds (of 200-500 ms) can be guaranteed with a very high probability at only a moderate content replication cost. The distribution algorithm achieves a four to fivefold reduction in the number of response-time violations compared to prior content distribution approaches that attempt to minimize average latency. To the authors' knowledge, this paper presents the first wide-area performance evaluation of an algorithm designed to bound maximum content access latency, as opposed to optimizing an average performance metric.
1236122
Range-free localization and its impact on large scale sensor networks
With the proliferation of location dependent applications in sensor networks, location awareness becomes an essential capability of sensor nodes. Because coarse accuracy is sufficient for most sensor network applications, solutions in range-free localization are being pursued as a cost-effective alternative to more expensive range-based approaches. In this paper, we present APIT, a novel localization algorithm that is range-free. We show that our APIT scheme performs best when an irregular radio pattern and random node placement are considered, and low communication overhead is desired. We compare our work, via extensive simulation, with three state-of-the-art range-free localization schemes to identify the preferable system configurations of each. In addition, we provide insight into the impact of localization accuracy on various location dependent applications and suggestions on improving their performance in the presence of such inaccuracy.
1650647
Load balancing in bounded-latency content distribution
In this paper we present a balanced data replication scheme that provides real-time latency bounds on content retrieval in content distribution networks. Many network applications have ever-increasing requirements on latency sensitive data services. Data replication services have been widely used as an important performance enhancement mechanism to reduce data access latency and throughput. We investigate the problem of provisioning an underlying balanced data replication service to provide a global latency bound on data retrieval in content distribution networks. The solution involves constructing an overlay network based on the given latency bound, and a mechanism to assign content objects to the network nodes so that the workload of all the network nodes is balanced. Our evaluation results drawn from detailed simulations show the efficacy of our load-balancing scheme in meeting the latency bound requirements with high confidence under heavy load
16039010
Design, Implementation and Evaluation of a Real-Time Active Content Distribution Service
The phenomenal growth of the world-wide web has made it the most popular Internet application today. Web caching and content distribution services have been recognized as valuable techniques to mitigate the explosion of web traffic. An increasing fraction of web traffic today is dynamically generated and therefore intrinsically difficult to replicate or cache using present static approaches. Scalable delivery of such active content poses a myriad of challenges, including content replication, update propagation, and consistency management. This paper makes two contributions: it (1) describes a scalable architecture for transparent demand-driven distribution of active content; and (2) presents a system that can provide real-time delay guarantees on content access. Our approach involves migrating the scripts which generate dynamic web traffic, and their data, from the origin servers to active content distribution proxies nearest to the clients. We also present mechanisms on these proxies to enforce real-time delay guarantees for client requests. Our system is implemented and deployed on Planetlab (2004), a real-world distributed Internet testbed. Experimental data show that significant improvements are observed in effective throughput and client response time, and that delay bounds on content access can be guaranteed with a very high probability.
14725341
Towards content distribution networks with latency guarantees
This paper investigates the performance of a content distribution network designed to provide bounded content access latency. Content can be divided into multiple classes with different configurable per-class delay bounds. The network uses a simple distributed algorithm to dynamically select a subset of its proxy servers for different classes such that a global per-class delay bound is achieved on content access. The content distribution algorithm is implemented and tested on PlanetLab, a world-wide distributed Internet testbed. Evaluation results demonstrate that despite Internet delay variability, subsecond delay bounds (of 200-500ms) can be guaranteed with a very high probability at only a moderate content replication cost. The distribution algorithm achieves a 4 to 5 fold reduction in the number of response-time violations compared to prior content distribution approaches that attempt to minimize average latency. This paper presents the first wide-area performance evaluation of an algorithm designed to bound maximum content access latency, as opposed to optimizing an average performance metric.
2426770
MMSN: Multi-Frequency Media Access Control for Wireless Sensor Networks
Multi-frequency media access control has been well understood in general wireless ad hoc networks, while in wireless sensor networks, researchers still focus on single frequency solutions. In wireless sensor networks, each device is typically equipped with a single radio transceiver and applications adopt much smaller packet sizes compared to those in general wireless ad hoc networks. Hence, the multi-frequency MAC protocols proposed for general wireless ad hoc networks are not suitable for wireless sensor network applications, which we further demonstrate through our simulation experiments. In this paper, we propose MMSN, which takes advantage of multi-frequency availability while, at the same time, takes into account the restrictions in wireless sensor networks. In MMSN, four frequency assignment options are provided to meet different application requirements. A scalable media access is designed with efficient broadcast support. Also, an optimal non-uniform backoff algorithm is derived and its lightweight approximation is implemented in MMSN, which significantly reduces congestion in the time synchronized media access design. Through extensive experiments, MMSN exhibits prominent ability to utilize parallel transmission among neighboring nodes. It also achieves increased energy efficiency when multiple physical frequencies are available.
29576760
A configurable AES processor for enhanced security
6577464
An HMAC processor with integrated SHA-1 and MD5 algorithms
Cryptographic algorithms are prevalent and important in digital communications and storage, e.g., both SHA-1 and MD5 algorithms are widely used hash functions in IPSec and SSL for checking the data integrity. In this paper, we propose a hardware architecture for the standard HMAC function that supports both. Our HMAC design automatically generates the padding words and reuses the key for consecutive HMAC jobs that use the same key. We have also implemented the HMAC design in silicon. Compared with existing designs, our HMAC processor has lower hardware cost---12.5% by sharing of the SHA-1 and MD5 circuitry and a little performance penalty.
2158099
Keyphrase Extraction Using Semantic Networks Structure Analysis
Keyphrases play a key role in text indexing, summarization and categorization. However, most of the existing keyphrase extraction approaches require human-labeled training sets. In this paper, we propose an automatic keyphrase extraction algorithm, which can be used in both supervised and unsupervised tasks. This algorithm treats each document as a semantic network. Structural dynamics of the network are used to extract keyphrases (key nodes) unsupervised. Experiments demonstrate the proposed algorithm averagely improves 50% in effectiveness and 30% in efficiency in unsupervised tasks and performs comparatively with supervised extractors. Moreover, by applying this algorithm to supervised tasks, we develop a classifier with an overall accuracy up to 80%.
15052014
Optimization of Regular Expression Pattern Matching Circuits on FPGA
Regular expressions are widely used in network intrusion detection system (NIDS) to represent patterns of network attacks. Since traditional software-only NIDS cannot catch up to the speed advance of networks, many previous works propose hardware architectures on FPGA to accelerate attack detection. The challenge of hardware implementation is to accommodate the regular expressions to FPGAs of the large number of attacks. Although the minimization of logic equations has been studied intensively in the CAD area, the minimization of multiple regular expressions has been largely neglected. This paper presents an architecture allowing our algorithm to extract and share common sub-regular expressions. Experimental results show that our sharing scheme significantly reduces the area of regular expression circuits
10023746
Test and diagnosis of word-oriented multiport memories
Conventionally, the test of multiport memories is considered difficult because of the complex behavior of the faulty memories and the large number of inter-port faults. This paper presents an efficient approach for testing and diagnosing multiport RAMs. Our approach takes advantage of the higher access bandwidth due to the increased number of read/write ports, which also provides higher observability and controllability that effectively reduces the test time. Our key idea is that a sequence of March operations for any memory cell can be folded and executed within a single access cycle. We have also developed an efficient test algorithm for port-specific faults as well as traditional cell faults. The port-specific faults include the stuck-open, address decoder, and inter-port faults, for both bit-oriented and word-oriented RAMs. Experimental results for our folding scheme show that the test time reduction is about 28% for a commercial 8 KB embedded SRAM. An efficient diagnostic algorithm is also proposed for the port-specific faults and traditional cell faults.