8030523
Video management in peer-to-peer systems
Providing scalable video services in a peer-to-peer (P2P) environment is challenging. Since videos are typically large and require high communication bandwidth for delivery, many peers may be unwilling to cache them in whole to serve others. In this paper, the authors addressed two fundamental research problems in providing scalable P2P video services, namely (1) how a host can find enough video pieces, which may scatter among the whole system, to assemble a complete video, and (2) given a limited buffer size, what part of a video a host should cache. A new distributed video management technique was proposed. This scheme organizes hosts into a number of cells, each of which is a distinct set of hosts which together can supply a video in its entirety. A client looking for a video can stop its search as soon as it finds a host that caches any part of the video. Caching operations can be coordinated within each cell to balance data redundancy in the system. The extensive study on a Gnutella-like simulation network shows convincingly the performance advantage of the new scheme.
271858
Providing scalable on-demand video services for heterogeneous receivers
To provide scalable video-on-demand services, precious system bandwidth must be shared among video requests. Although many efficient bandwidth-sharing techniques have been proposed, they are all designed for homogeneous receivers, i.e., the clients are assumed to have the same receiving bandwidth. For networks with client heterogeneity, these techniques either cannot work or have to compromise their performance. In this paper, we address this problem and propose an efficient solution allowing each client to use its whole receiving bandwidth to download data. To serve a client, the server first selects a set of serving channels for the client according to its actual receiving bandwidth. The video data needed for this client are then scheduled and dynamically adjusted for delivery over these channels. We evaluate the performance of the new technique using simulation and compare it with an existing scheme. Our study shows that by effectively leveraging client heterogeneity, the new technique achieves significantly smaller service latency
6021546
Leveraging 1-hop neighborhood knowledge for efficient flooding in wireless ad hoc networks
Flooding is a fundamental and frequently invoked operation in wireless ad hoc networks. Existing flooding techniques either are unreliable, generate overwhelming unnecessary retransmission, or incur excessive network control overhead. In this paper, we address these crucial problems and propose a new flooding technique called edge forwarding. The new scheme minimizes the flooding traffic by leveraging location information to limit broadcast retransmission to only hosts near the perimeter of each broadcast coverage. Unlike most existing techniques, edge forwarding requires each host to track only neighboring nodes within its one-hop distance. Therefore, it is more adaptive to host mobility and incurs less network control overhead. In particular, it can be easily incorporated into many existing routing protocols without any additional control overhead. Our performance studies indicate that with our strategy, a substantial portion of the unnecessary broadcast retransmission can be eliminated.
9627520
Processing range-monitoring queries on heterogeneous mobile objects
We consider in this paper how to leverage heterogeneous mobile computing capability for efficient processing of real-time range-monitoring queries. In our environment, each mobile object is associated with a resident domain and when an object moves, it monitors its spatial relationship with its resident domain and the monitoring areas inside it. An object reports its location to server whenever its movement affects any query results (i.e., crossing any query boundaries) or it moves out of its resident domain. In the first case, the server updates the affected query results accordingly while in the second case, the server determines a new resident domain for the object. This distributive approach is able to provide accurate query results and real-time monitoring updates with minimal location update and server processing costs. In addition, the new scheme allows a mobile object to negotiate a resident domain based on its computing capability. Thus, a more capable object can have a larger resident domain reducing its chance of having to request a new resident domain because of moving out of it. This feature makes the new approach highly adaptive to the heterogeneity of mobile objects. In our performance study, we compare it with an existing approach using simulation. The study shows that the new technique is many times better in reducing mobile communication and server processing costs.
7607384
Sharing Location Dependent Experiences in MANET
This paper investigates a new problem of sharing location dependent experiences among mobile hosts in mobile adhoc networks. An experience is location and observer dependent. In other words, experiences of different people witnessing the same event may be quite different. The ability to retrieve prior experiences observed in a given area in advance is very useful for newcomers wishing to enter the same vicinity. Solving this problem is vital for important applications such as hurricane rescue missions, combat missions, and deep space or deep sea exploration. In this paper, we propose a distributed solution that lets mobile hosts share their experiences efficiently. Our simulation results show that our approach significantly outperforms a centralized approach.
14591533
Leveraging broadband access for true on-demand delivery of Internet videos
We consider in this paper how the increasingly popular broadband access can be leveraged for scalable and cost-effective video service. Although much work has been done for such service, the existing techniques either are not designed for on-demand video delivery, or do not take into account the vastly improved client receiving capability. In this paper, we address this problem and develop three novel video delivery techniques with two ultimate goals: minimizing service latency and maximize data sharing. With the new techniques, a client can be served as soon as server resource becomes available and meanwhile, all its receiving bandwidth can be used for data receiving. In particular, in the proposed dynamic scheduling algorithm, the efficiency of data sharing is further improved by also exploring server bandwidth for early delivery of video segments. This innovation is contradicted to the intuition that each video segment should be delivered as late as possible in order to maximize data sharing. We evaluate the performance of our new techniques using simulation and our study convincingly shows that with the new schemes, zero service latency can indeed be achieved with very minimal system resource.
28503947
An integrated approach with feedback control for robust Web QoS design
There is a growing demand for provisioning of different levels of quality of service (QoS) on scalable Web servers to meet changing resource availability and to satisfy different client requirements. In this paper, we investigate the problem of providing proportional QoS differentiation with respect to response time on Web servers. We first present a processing rate allocation scheme based on the foundations of queueing theory. It provides different processing rates to requests of different client classes so as to achieve the differentiation objective. At application level, process is used as the resource allocation principal for achieving processing rates on Apache Web servers. We design and implement an adaptive process allocation approach, guided by the queueing-theoretical rate allocation scheme, on an Apache server. This application-level implementation, however, shows weak QoS predictability because it does not have fine-grained control over the consumption of resources that the kernel consumes and hence the processing rate is not strictly proportional to the number of processes allocated. We then design a feedback controller and integrate it with the queueing-theoretical approach. It adjusts process allocations according to the difference between the target response time and the achieved response time using a proportional integral derivative controller. Experimental results demonstrate that this integrated approach can enable Web servers to provide robust proportional response time differentiation.
11155724
Non-modularity in aspect-oriented languages: integration as a crosscutting concern for AspectJ
Aspect-oriented (AO) methods and languages seek to enable the preservation of design modularity through mappings to program structures, especially where common (object-oriented) languages fail to do so. The general claim is made that AO approaches enable the modularization of crosscutting concerns. The problem that we address is that it is unclear to what extent such claims are valid. We argue that there are meaningful bounds on the abilities of past, present, and future languages to succeed in this regard---bounds that we need to understand better. To make this idea concrete we exhibit a significant bound: Component integration (Sullivan & Notkin 1992, 1994) is not adequately modularizable in AspectJ
8404482
LSWS: A Linux-based Secure Web Switch
6311601
An adaptive process allocation strategy for proportional responsiveness differentiation on Web servers
There is a growing demand for provisioning of different levels of quality of service (QoS) on scalable Web servers to meet changing resource availability and satisfy different client requirements. The proportional differentiation model is getting momentum because of its fairness and differentiation predictability. It states that QoS of different traffic classes should be kept proportional to their pre-specified differentiation parameters, independent of the class loads. In this paper, we present a processing rate allocation scheme for providing proportional response time differentiation on Web servers. A challenging issue is how to achieve processing rates for different request classes in the implementation. We propose a process allocation strategy, which dynamically and adaptively changes the number of processes allocated for handling different request classes while ensuring the ratios of process allocation specified by the processing rate allocation scheme. We implement the process allocation strategy at application level on Apache Web servers. Experimental results show that the processing rate can be achieved by the adaptive process allocation strategy and the Web servers can provide predictable and controllable proportional response time differentiation.
16856059
An Area-Based Collaborative Sleeping Protocol for Wireless Sensor Networks
An effective approach for energy conservation in wireless sensor networks is putting redundant sensor nodes to sleep while the active nodes provide certain degree of coverage. This paper presents an Area-based Collaborative Sleeping protocol (ACOS) that can control the degree of coverage for diverse applications. The ACOS protocol, based on the net sensing area of a sensor, controls the mode of sensors to maximize the coverage, minimize the energy consumption, and to extend the lifetime of the sensor network. The net sensing area of a sensor is the area of the region exclusively covered by the sensor itself. We study the parameter tuning in ACOS to guide to configure the network for diverse applications. The simulation shows that our protocol has better coverage of the surveillance area while waking fewer sensors than other sleeping protocols. It extends the lifetime of sensor networks significantly