Caching collaboration and cache allocation in peer-to-peer video 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, we address two fundamental research problems in providing scalable P2P video services: (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 and what existing data should be expunged to make necessary space. We address these problems with two new ideas: Cell caching collaboration and Controlled Inverse Proportional (CIP) cache allocation. The Cell concept allows cost-effective caching collaboration in a fully distributed environment and can dramatically reduce video lookup cost. On the other hand, CIP cache allocation challenges the conventional caching wisdom by caching unpopular videos in higher priority. Our approach allows the system to retain many copies of popular videos to avoid creating hot spots and at the same time, prevent unpopular videos from being quickly evicted from the system. We have implemented a Gnutella-like simulation network and use it as a testbed to evaluate the proposed technique. Our extensive study shows convincingly the performance advantage of the new scheme.

Exploiting client caches to build large Web caches

New demands brought by the continuing growth of the Internet will be met in part by more effective and comprehensive use of caching. This paper proposes to exploit client browser caches in the context of cooperative proxy caching by constructing the client caches within each organization (e.g., corporate networks) as a peer-to-peer (P2P) client cache. Via trace-driven simulations we evaluate the potential performance benefit of cooperative proxy caching with/without exploiting client caches. We show that exploiting client caches in cooperative proxy caching can significantly improve performance, particularly when the size of individual proxy caches is limited compared to the universe of Web objects. We further devise a cooperative hierarchical greedy-dual replacement algorithm (Hier-GD), which not only provides some cache coordination but also utilizes client caches. Through Hier-GD, we explore the design issues of how to exploit client caches in cooperative proxy caching to build large Web caches. We show that Hier-GD is technically practical and can potentially improve the performance of cooperative proxy caching by utilizing client caches.

Design and analysis of a variable bit rate caching algorithm for continuous media data

In this paper, the problem of caching continuous media data in a (main) memory and disk caching system is addressed. Caching schemes can significantly reduce the load on the network as well as on the servers, also the retrieval of documents from the cache requires short response time. In interval-level caching algorithms, an interval of data between two adjacent streams is the basic caching entity. In this paper, we design a novel algorithm, referred to as variable bit rate caching (VBRC) algorithm, which belongs to the interval-level caching algorithms. The proposed VBRC algorithm can be used in the system for memory caching or disk caching. VBRC can handle variable retrieval bandwidth as well as constant retrieval bandwidth . In designing the VBRC algorithm, we propose the strategies of reducing the number of switching operation, which will probably cause discontinuity of retrieving data. Also, we propose a just-in-time scheme for resource allocation in our VBRC algorithm and show that the caching performance in comparison with the reservation scheme adopted in the resource-based caching (RBC) algorithm is significantly improved. Our simulation study compares the recent and most popular generalized interval caching, RBC, and VBRC, on several influencing factors such as cache space size, cache I/O bandwidth, request arrival rate, and percentage of requests for large documents, with respect to the byte hit ratio and the number of switching operations. The simulation result confirms our analysis.

Optimized scalable cache management for video streaming system

An important research issue in video streaming is how to efficiently utilize the network resources to provide clients instant access to multiple video objects. Caching strategy and transmission scheme are the two essential points inside the video streaming framework. Recent research efforts on them are not sufficient due to their inflexible support for scalable encoded video streams and heterogeneous requests from clients. In this paper, we propose an optimized caching strategy (OCS) and a scalable transmission scheme (STS) for scalable coded video streaming. By exploring the characteristics of video streaming workload and system design objectives, OCS and STS work efficiently to minimize both network bandwidth cost and user access latency. Firstly, we analyze the caching problem for the proxy-assisted video streaming system and derive a maneuverable caching scenario. Secondly, we develop an efficient transmission scheme for scalable coded videos. Thirdly, we formulate a multi-objective optimization model with closed-form expressions to obtain the optimized caching strategy. Finally, with designed algorithms, an excellent compromise between two competing objectives (minimizing the bandwidth cost and the access latency) is achieved. We start our evaluation by studying the optimized caching strategy for a single video object. Then we apply the strategy to multiple video objects and illustrate the tradeoff between the optimization objectives. Our evaluation results show that compared with other caching strategies, the proposed optimized scalable caching strategy can achieve a significant reduction in bandwidth cost with even a small proxy cache size. Meanwhile, the best performance (in terms of bandwidth cost) is obtained together with the proposed scalable batch-patching transmission scheme.

On index load balancing in scalable P2P media distribution

Peer-Peer (P2P) technologies have recently been in the limelight for their disruptive power in particular they have emerged as a powerful multimedia content distribution mechanism. However, the widespread deployment of P2P networks are hindered by several issues, especially the ones that influence end-user satisfaction, including reliability. In this paper, we propose a solution for an efficient and user-oriented keyword lookup service on P2P networks. The proposed mechanism has been designed to achieve reliability via index load balancing and address the scalability issues of extremely popular keywords in the index. The system performance have been analytically derived as well implemented using the OpenDHT framework on PlanetLab.

OCS: An effective caching scheme for video streaming on overlay networks

Video streaming is vital for many important applications such as distance learning, digital video libraries, and movie-on-demand. Since video streaming requires significant server and networking resources, caching has been used to reduce the demand on these resources. In this paper, we propose a novel collaboration scheme for video caching on overlay networks, called Overlay Caching Scheme (OCS), to further minimize service delays and loads placed on an overlay network for video streaming applications. OCS is not a centralized nor a hierarchical collaborative scheme. Despite its design simplicity, OCS effectively uses an aggregate storage space and capability of distributed overlay nodes to cache popular videos and serve nearby clients. Moreover, OCS is light-weight and adaptive to clients’ locations and request patterns. We also investigate other video caching techniques for overlay networks including both collaborative and non-collaborative ones. Compared with these techniques on topologies inspired from actual networks, OCS offers extremely low average service delays and approximately half the server load. OCS also offers smaller network load in most cases in our study.

PECOLE: P2P multimedia collaborative environment

PECOLE (Peer-to-pEer COLlaborative Environment) is a fully decentralized multimedia collaborative environment that supports a wide range of collaborative multimedia applications, including chat, shared browsing, shared telepointer, multipoint-to-multipoint audio/video conferencing and multilingual collaboration. PECOLE can intelligently run on very constrained resources, is highly resilient, scalable and does not rely on dedicated servers. Instead, PECOLE is built upon a Peer-to-Peer (P2P) overlay network, using SUN’s JXTA framework and SWT technology. In this paper, we present the architecture and implementation of PECOLE with the performance results of the tests we conducted.

P2Cast: peer-to-peer patching for video on demand service

Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose P2Cast—an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in P2Cast: (1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches) in the face of disruption from an early departing client. Our simulation experiments show that P2Cast can serve many more clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients can cache more than 10% of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying the shifted forwarding technique. The threshold in P2Cast, i.e., the length of time during which arriving clients form a single session, can serve as a “knob” to adjust the balance between the scalability and the clients’ viewing quality.

The 2007 IEEE CEC simulated car racing competition

This paper describes the simulated car racing competition that was arranged as part of the 2007 IEEE Congress on Evolutionary Computation. Both the game that was used as the domain for the competition, the controllers submitted as entries to the competition and its results are presented. With this paper, we hope to provide some insight into the efficacy of various computational intelligence methods on a well-defined game task, as well as an example of one way of running a competition. In the process, we provide a set of reference results for those who wish to use the simplerace game to benchmark their own algorithms. The paper is co-authored by the organizers and participants of the competition.

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Interacting with mobile services: an evaluation of camera-phones and visual tags

We present a study of using camera-phones and visual-tags to access mobile services. Firstly, a user-experience study is described in which participants were both observed learning to interact with a prototype mobile service and interviewed about their experiences. Secondly, a pointing-device task is presented in which quantitative data was gathered regarding the speed and accuracy with which participants aimed and clicked on visual-tags using camera-phones. We found that participants’ attitudes to visual-tag-based applications were broadly positive, although they had several important reservations about camera-phone technology more generally. Data from our pointing-device task demonstrated that novice users were able to aim and click on visual-tags quickly (well under 3 s per pointing-device trial on average) and accurately (almost all meeting our defined speed/accuracy tradeoff of 6% error-rate). Based on our findings, design lessons for camera-phone and visual-tag applications are presented.

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Evolving strategy for a probabilistic game of imperfect information using genetic programming

We provide the complete record of methodology that let us evolve BrilliAnt, the winner of the Ant Wars contest. Ant Wars contestants are virtual ants collecting food on a grid board in the presence of a competing ant. BrilliAnt has been evolved through a competitive one-population coevolution using genetic programming and fitnessless selection. In this paper, we detail the evolutionary setup that lead to BrilliAnt’s emergence, assess its direct and indirect human-competitiveness, and describe the behavioral patterns observed in its strategy.

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Connecting IPvX Networks Over IPvY with a P2P Method

During the transition from IPv4 to IPv6, the IPv6 islands inside the IPv4 networks need to communicate with each other and with the native IPv6 network. The drawback of existing IPv6 transition methods is that relay gateways become potential communication bottlenecks. In this paper, a new method—PS64—is presented to connect IPv6 islands together over IPv4 network and reduce the reliance on these relays by shifting the burden to edge gateways on each island. In this method, direct tunnels are set up between the IPv6 islands, and a P2P network is maintained between edge gateways of these islands to propagate information of tunnel end points. After describing the algorithm, we analyze the connectivity of the P2P network, the scalability of this algorithm, and present the prototype and experiments. The results of our analysis and experiments show that the proposed method is reliable, scalable and effective. Obviously, this technique works for all IPvX over IPvY situations.

Connecting the family with awareness systems

Awareness systems have attracted significant research interest for their potential to support interpersonal relationships. Investigations of awareness systems for the domestic environment have suggested that such systems can help individuals stay in touch with dear friends or family and provide affective benefits to their users. Our research provides empirical evidence to refine and substantiate such suggestions. We report our experience with designing and evaluating the ASTRA awareness system, for connecting households and mobile family members. We introduce the concept of connectedness and its measurement through the Affective Benefits and Costs of communication questionnaire (ABC-Q). We inform results that testify the benefits of sharing experiences at the moment they happen without interrupting potential receivers. Finally, we document the role that lightweight, picture-based communication can play in the range of communication media available.

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Methods for quantitative usability requirements: a case study on the development of the user interface of a mobile phone

Quantitative usability requirements are a critical but challenging, and hence an often neglected aspect of a usability engineering process. A case study is described where quantitative usability requirements played a key role in the development of a new user interface of a mobile phone. Within the practical constraints of the project, existing methods for determining usability requirements and evaluating the extent to which these are met, could not be applied as such, therefore tailored methods had to be developed. These methods and their applications are discussed.

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Enhanced DHT-based P2P Architecture for Effective Resource Discovery and Management

Recently, Peer-to-Peer (P2P) has become a popular paradigm for building distributed systems, aiming to provide resource localization and sharing in large-scale networks. However, advanced searching for resources remains an open issue. The flooding technique used by some P2P systems is expensive in bandwidth usage, and shows a serious lack in scalability. Also, more efficient systems based on distributed hash tables (DHT) lack in query expressiveness and flexibility. This paper addresses this issue by discussing existing solutions, and proposing a novel approach to support advanced multi-keyword queries in the context of P2P systems. It extends the existing, and widely established DHT-based localization frameworks. This new approach provides an effective resource localization framework; it can substantially reduce bandwidth consumption and improve load balancing over the network. Moreover, various kinds of applications can be deployed on top of this generic framework. As a relevant use case, this paper describes a novel service discovery and management application.

Scientific models and ethical issues in hybrid bionic systems research

Research on hybrid bionic systems (HBSs) is still in its infancy but promising results have already been achieved in laboratories. Experiments on humans and animals show that artificial devices can be controlled by neural signals. These results suggest that HBS technologies can be employed to restore sensorimotor functionalities in disabled and elderly people. At the same time, HBS research raises ethical concerns related to possible exogenous and endogenous limitations to human autonomy and freedom. The analysis of these concerns requires reflecting on the availability of scientific models accounting for key aspects of sensorimotor coordination and plastic adaptation mechanisms in the brain.

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ONTRACK: Dynamically adapting music playback to support navigation

Listening to music on personal, digital devices whilst mobile is an enjoyable, everyday activity. We explore a scheme for exploiting this practice to immerse listeners in navigation cues. Our prototype, ONTRACK, continuously adapts audio, modifying the spatial balance and volume to lead listeners to their target destination. First we report on an initial lab-based evaluation that demonstrated the approach’s efficacy: users were able to complete tasks within a reasonable time and their subjective feedback was positive. Encouraged by these results we constructed a handheld prototype. Here, we discuss this implementation and the results of field-trials. These indicate that even with a low-fidelity realisation of the concept, users can quite effectively navigate complicated routes.

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Multimodal support to group dynamics

The complexity of group dynamics occurring in small group interactions often hinders the performance of teams. The availability of rich multimodal information about what is going on during the meeting makes it possible to explore the possibility of providing support to dysfunctional teams from facilitation to training sessions addressing both the individuals and the group as a whole. A necessary step in this direction is that of capturing and understanding group dynamics. In this paper, we discuss a particular scenario, in which meeting participants receive multimedia feedback on their relational behaviour, as a first step towards increasing self-awareness. We describe the background and the motivation for a coding scheme for annotating meeting recordings partially inspired by the Bales’ Interaction Process Analysis. This coding scheme was aimed at identifying suitable observable behavioural sequences. The study is complemented with an experimental investigation on the acceptability of such a service.

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Subscriber mobility management for a P2P publish/subscribe overlay in mobile tactical networks

P2P (Peer-to-Peer) overlay is a promising distributed computing and communication paradigm that allows for a group of participants to share information and coordinate their resources. Dissemination of information among end users can also be greatly facilitated by the publish/subscribe model. In this paper, we employ the publish/subscribe model in a P2P mobile tactical networking environment. Considering the particular requirements for mobile tactical networks, we investigate the problem of subscriber mobility management and propose a novel proactive handoff approach for improved system responsiveness and reliability. A comprehensive performance evaluation of the proposed mechanism is presented. The obtained results demonstrate significant performance benefits of the proposed scheme.

Resource Sharing Architecture For Cooperative Heterogeneous P2P Overlays

Resource requirements and availability in heterogeneous networks may frequently vary over their lifetime; thus producing equally variant overloaded and under-loaded situations. Typical architectures cannot cope with the frequent availability fluctuation of reusable, non-replicable and highly dynamic resources (such as network capacity). This paper proposes an unstructured P2P overlay for sharing resources between underutilized and overloaded networks. Its aim is to satisfy the excessive resource demands of some networks by using free resources from others given the high failure rate and unstable availability of these resources in wide networks. We describe and analyze the proposed Capacity Sharing Overlay Architecture and show, with extensive simulations, its ability to provide remote underutilized capacity to underlying networks, even in the presence of high node failure rates, helping the networks to handle more user queries.