54735
An architecture for real-time active content distribution
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 for replication 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: (1) it describes a scalable architecture for transparent demand-driven distribution of active content; (2) the system can provide real-time delay guarantee on content access. Our approach involves migrating the scripts which generate the dynamic Web traffic, and their data, from the server to active content distribution proxies nearest to the clients and mechanisms on these proxies to enforce real-time delay guarantees for client requests. Our system is implemented and deployed on PlanetLab, a real-world distributed Internet testbed. Experimental data show that significant improvements are observed in effective throughput and client response time, and delay bounds on content access can be guaranteed with a very high probability.
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.
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.
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.
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
1476959
High-level synthesis of distributed logic-memory architectures
With the increasing cost of global communication on-chip, high-performance designs for data-intensive applications require architectures that distribute hardware resources (computing logic, memories, interconnect, etc.) throughout a chip, while restricting computations and communications to geographic proximities. In this paper, we present a methodology for high-level synthesis (HLS) of distributed logic-memory architectures, i.e., architectures that have logic and memory distributed across several partitions in a chip. Conventional HLS tools are capable of extracting parallelism from a behavior for architectures that assume a monolithic controller/datapath communicating with a memory or memory hierarchy. This work provides techniques to extend the synthesis frontier to more general architectures that can extract both coarse- and fine-grained parallelism from data accesses and computations in a synergistic manner. Our methodology selects many possible ways of organizing data and computations, carefully examines the trade-offs (i.e., communication overheads, synchronization costs, area overheads) in choosing one solution over another, and utilizes conventional HLS techniques for intermediate steps.We have evaluated the proposed framework on several benchmarks by generating register-transfer level (RTL) implementations using an existing commercial HLS tool with and without our enhancements, and by subjecting the resulting RTL circuits to logic synthesis and layout. The results show that circuits designed as distributed logic-memory architectures using our framework achieve significant (upto, 5.31X average of 3.45X) performance improvements over well-optimized conventional designs with small area overheads (upto 19.3%, 15.1% on average).
14645139
Generation of distributed logic-memory architectures through high-level synthesis
With the increasing cost of on-chip global communication, high-performance designs for data-intensive applications require architectures that distribute hardware resources (computing logic, memories, interconnect, etc.) throughout the chip, while restricting computations and communications to geographic proximities. In this paper, we present a methodology for high-level synthesis (HLS) of distributed logic-memory architectures, i.e., architectures that have logic and memory distributed across several partitions in a chip. Conventional HLS tools are capable of extracting parallelism from a behavior for architectures that assume a monolithic controller/datapath communicating with a memory or memory hierarchy. This paper provides techniques to extend the synthesis frontier to more general architectures that can extract both coarse and fine-grained parallelism from data accesses and computations in a synergistic manner. Our methodology selects many possible ways of organizing data and computations, carefully examines the tradeoffs (i.e., communication overheads, synchronization costs, area overheads) in choosing one solution over another, and utilizes conventional HLS techniques for intermediate steps. We have evaluated the proposed framework on several benchmarks by generating register-transfer level (RTL) implementations using an existing commercial HLS tool with and without our enhancements, and by subjecting the resulting RTL circuits to logic synthesis and layout. The results show that circuits designed as distributed logic-memory architectures using our framework achieve significant (up to 5.3/spl times/, average of 3.5/spl times/) performance improvements over well-optimized conventional designs with small area overheads (up to 19.3%, 15.1% on average). At the same time, the reduction in the energy-delay product is by an average of 5.9/spl times/ (up to 11.0/spl times/).
19145806
An adaptive architecture for multi-stream authoring and presentations in distributed networks
New global trends in communications technology and liberalization are forcing dramatic changes in our lives. Applications tend to be lightweight and mobile, resulting in greater convenience. We present a new architecture to advance the traditional authoring system towards these trends. In the proposed architecture, the authoring system is capable of editing media content distributed in the networks. It forms a new model of authoring, i.e., the distributed authoring model. The distributed authoring model is described and compared with the traditional authoring model. We introduce quality-on-demand streaming in the architecture for the purpose of distributed authoring. Furthermore, we address the problems of applying multiple source streaming and quality adaptation in the architecture and show our design for resolving these problems. An implementation conforming to this architecture is also described.
9984897
Structure Alignment Using Bilingual Chunking
A new statistical method called "bilingual chunking" for structure alignment is proposed. Different with the existing approaches which align hierarchical structures like sub-trees, our method conducts alignment on chunks. The alignment is finished through a simultaneous bilingual chunking algorithm. Using the constrains of chunk correspondence between source language (SL) and target language (TL), our algorithm can dramatically reduce search space, support time synchronous DP algorithm, and lead to highly consistent chunking. Furthermore, by unifying the POS tagging and chunking in the search process, our algorithm alleviates effectively the influence of POS tagging deficiency to the chunking result.The experimental results with English-Chinese structure alignment show that our model can produce 90% in precision for chunking, and 87% in precision for chunk alignment.
195352079
The impact of network variabilities on TCP clocking schemes