14377220
On large scale deployment of parallelized file transfer protocol
The parallelized file transfer protocol (P-FTP) is a novel network resource aware parallel technique for improving file transfer performance on the Internet. Before starling the parallel file transfer sessions, it considers the available resources in the network (available bandwidth) and at the file servers (memory and CPU utilization). The client dynamically changes the file portions being downloaded from different file servers by monitoring the FTP flows and detecting slow servers and congested links. Early experimentation on Planet-Lab (2004) for a single P-FTP client suggests that the download time can be reduced by more than 50% for large files. In this paper, our goal is to evaluate whether P-FTP can be widely adopted within the Internet, To this end, we have carried out a simulation-based study to investigate the performance of P-FTP when it is adopted by a large user base. We find that, by virtue of its self-tuning capability, P-FTP continues to exhibit improved performance even with many simultaneous clients. Our results also demonstrate that introducing a large number of P-FTP users has no adverse effect on the performance perceived by users of the traditional single server file transfer. We attribute this improvement to the fact that P-FTP dynamically adapts the parallel sessions in response to changes in network state and server resources. This illustrates that P-FTP is highly scalable and is hence suitable for widespread deployment in the Internet.
7646347
Provisioning overlay distribution networks
Future entertainment services are expected to be increasingly interactive, on demand and personalized. This paper aims to address the challenge of provisioning network and server resources to support the distribution of these services over the Internet. We propose the Overlay Distribution Network (ODN) as a cost-effective means to deliver these services. Because ODNs are created over shared network and server infrastructure, the provisioning problem becomes significantly complex. The paper formulates this problem as a joint resource provisioning and content replication optimization. The resulting formulation is proved to be NP-complete. We solved this problem with an efficient Lagrangian heuristic. Further, content clustering is employed to improve the heuristic run time. Initial results show that this is efficient. In some cases, clustering allows solutions with very similar quality to be achieved at a 20 times reduction in complexity.
14928068
Traffic engineering for MPLS-based virtual private networks
This paper considers the traffic engineering of MPLS-based Virtual Private Networks (VPNs) with multiple classes of service in an offline and centralised setting. We focus on two main issues. Firstly, we point out that the one label switched path (LSP) per ingress-egress pair constraint can be relaxed for the case of MPLS-based VPNs due to the ease in classifying flows on a per-VPN basis. This allows us to use LSP with finer granularity and thus better load balancing. Secondly, we point out that the single objective traffic engineering formulations proposed in literature address only one particular aspect of the traffic engineering problem. In this paper, we propose a multiobjective traffic engineering problem which takes resource usage, link utilisation and number of LSPs into account. The proposed optimisation problem is NP-complete and involves a large number of variables. We propose an heuristic to solve this problem.
8147679
Deploying long-lived and cost-effective hybrid sensor networks
In this paper, we consider the problem of network deployment in hybrid sensor networks, consisting of both resource-rich and resource-impoverished sensor devices. The resource-rich devices, called micro-servers, are more expensive but have significantly greater bandwidth and energy capabilities compared to the low-cost, lowpowered sensors. Such hybrid sensor networks have the potential to support the higher bandwidth communications of broadband sensor networking applications, as
7989034
Internal popularity of streaming video and its implication on caching
As most proxy caches for streaming media cache only a part of the video, the most important issue for a caching algorithm is to determine which portion of the video should be cached. Due to different part of the video can have different popularity, the studying of the internal popularity characteristics of streaming videos is very important for the development of efficient cache mechanisms. In this paper, we showed that the internal popularity of the majority of the most popular videos obeys a k-transformed Zipf-like distribution through analyzing two 7-month long traces recorded at different streaming video servers of an entertainment video-on-demand provider. Based on this empirical internal popularity distribution model, we then proposed a new dynamical caching algorithm. The results of simulations proved that this algorithm can have better performance than algorithms based on other models and it has similar performance compare with fine-grained caching but requires significantly less state information.
38950443
Mechanical Verification of Distributed Algorithms in Higher-Order Logic
The only practical way to verify the correctness of distributed algorithms with a high degree of confidence is to construct machine-checked, formal correctness proofs. In this paper we explain how to do so using HOL an interactive proof assistant for higher order logic developed by Gordon and others. First, we describ how to build an infrastructure in HOL that supports reasoning about distributed algorithms,including formal theories of predicates, temporal logic, labeled transitions systems, simulation of programs, translation of properties, and graphs. Then we demonstrate, via an exemple, how to use the powerful intuition about eventsand causality to guide and structure correctness proofs of distributed algorithms. The example used is the verification of PIF (propagation of information with feedback), which is a simple but typical distributed algorithm due to Segall.
16192278
A distributed location service for reducing query failures in geographic ad hoc routing
Location service support is required for mobile nodes using geographic ad hoc routing. The mobile nodes need location information of destinations for sending data packets. Due to mobility or node failures, queries to the location servers may not always succeed. This paper presents a distributed location service (DLS) that employs dual servers to maintain position information of mobile nodes and to achieve efficient performance. With the scheme, the number of failed queries, including no response and erroneous results, can be reduced. DLS has been implemented and evaluated using the ns2 simulator. The experimental results show that DLS not only improved service availability but also location query latency.
34878054
Improving Data Transmission with Helping Nodes for Geographical Ad Hoc Routing
Ad hoc networks have been extensively deployed in recent years. In such networks, obtaining a high efficiency is difficult to achieve due to mobility. Many routing approaches have been proposed to improve the performance of ad hoc networks, including table-driven and demand-driven routing protocols. Geographic routing provides a suitable solution for large-scale and dynamic networks, and reduces link failure problems during packet routing. In wireless networks, nodes movement may cause a network partition, which hinders both data transmission and information availability within the network. Several schemes have been proposed for resolving the partition problem in wireless ad hoc networks. In general, the previous solutions either relied on the use of mobile devices with known trajectories or introduced additional specific mobile nodes. By contrast, this paper proposes a scheme for overcoming the problem of network partitions using only the available devices in the environment. With the scheme, the source node searches for another mobile node, designated as the helping node, which is able to meet the destination. The selected mobile node then carries the packet toward the destination. If the helping node changes its trajectory before it forwards the packet to the destination node, a hand-off scheme is activated and the data packet is transferred to another mobile node for onward transmission
7247879
A comparative content analysis of student interaction in synchronous and asynchronous learning networks
Interaction plays an important role in the success of distance learning. As most distance learning environments mainly utilize asynchronous computer-mediated communication (CMC) systems, interaction research that focuses on synchronous CMC is largely ignored. This study scrutinized the patterns of learner-learner interaction in a distance learning environment. Student interactions in synchronous and asynchronous CMC systems were compared. The results of the research suggest that constructivist-based instructional activities, such as student-moderated discussion and small-group cooperative learning, are conducive to interaction. Overall, a higher percentage of social-emotional interactions occurred in the synchronous mode than in the asynchronous mode. Students spent more time in task-oriented interaction in asynchronous discussions than they did in the synchronous mode. In moderating online seminars, student moderators who followed the guidelines of student-centered discussions (SCD) were able to encourage full participation in an online seminar. Recommendations for the design of instructional activities and interactive interfaces were also made in order to improve distance learning environments.
9105322
CSCL for community building and digital equity
The Minnesota Educators and Leaders Technology Initiative (MELTI) contributes to community building and digital equity through computer-supported collaborative learning (CSCL) activities and other project activities. The CSCL activities that include asynchronous, synchronous, and video conferencing are designed to address issues of integration faced by the MELTI participating schools which have high percentage of minority students. The notions of social inclusion and technology literacy play a key role in the CSCL activities design for the purpose of overcoming barriers to digital equity.