13565274
Optimized allocation of distributed applications across local area networks
Enterprise-wide distributed computing systems are inherently stochastic and the performance management of distributed applications running on the top of DCS is a complex and computationally hard task, in this paper, we define the enterprise distributed application and provide queueing analysis on the relationship between the application level performance parameters and the network and computer system parameters. We also provide a binary integer programming (BIP) model and a case study on how to allocate application components across an enterprise local area network.
14766680
QoS Driven Parallelization of Resources to Reduce File Download Delay
In this paper, we propose a novel approach for reducing the download time of large files over the Internet. Our approach, known as parallelized file transport protocol (P-FTP), proposes simultaneous downloads of disjoint file portions from multiple file servers. P-FTP server selects file servers for the requesting client on the basis of a variety of QoS parameters, such as available bandwidth and server utilization. The sensitivity analysis of our file server selection technique shows that it performs significantly better than random selection. During the file transfer, P-FTP client monitors the file transfer flows to detect slow servers and congested links and adjusts the file distributions accordingly. P-FTP is evaluated with simulations and real-world implementation. The results show at least 50 percent reduction in download time when compared to the traditional file-transfer approach. Moreover, we have also carried out a simulation-based study to investigate the issues related to large scale deployment of our approach on the Internet. Our results demonstrate that a large number of P-FTP users has no adverse effect on the performance perceived by non-P-FTP users. In addition, the file servers and network are not significantly affected by large scale deployment of P-FTP
9337287
Detection and Recovery for Disconnection Failures in a Web-based Medical Teleconsultation System
With the progress of advanced technology, people anticipate better quality in the medical health care service. Due to more robust requirements in medical environments, higher availability and reliability are expected. This paper describes a recovery scheme for disconnection failures in a Web-based medical teleconsultation system. With the support, the disconnected clients can re-enter the system to resume the unfinished discussion using the synchronization mechanisms. The experiments have shown that the mechanism performed successfully. The lazy synchronization further reduced the required time that the clients had to wait for joining the consultation after network disconnections
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.
37293977
Mechanical Verification of Distributed Algorithms in Higher-Order Logic
The only way to verify the correctness of a distributed algorithm with a high degree of confidence is to construct a correctness proof that is so formal and rigorous as to be checkable by a machine. The chief aim of this paper is to show, via a simple but typical example, how such proofs can be constructed and checked using HOL—a mechanical theorem-proving system for higher-order logic. The secondary aim is to demonstrate a method for reasoning about distributed algorithms based on the notions of events and causality. The goal is to perform as much reasoning as possible in the events-and-causality view and then translate the results back to the processors-and-messages view, since the former is more abstract and easier to reason about than the latter. The example we use to illustrate our ideas is the verification of a simple distributed summation algorithm for trees. A companion paper [6] describes the formal graph theory needed for this task.
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.
5473639
Large-scale data collection: a coordinated approach
In this paper we consider the problem of collecting a large amount of data from several different hosts to a single destination in a wide-area network. Often, due to congestion conditions, the paths chosen by the network may have poor throughput. By choosing an alternate route at the application level, we may be able to obtain substantially faster completion time. This data collection problem is a nontrivial one because the issue is not only to avoid congested link(s), but to devise a coordinated transfer schedule which would afford maximum possible utilization of available network resources. In this paper we present an approach for computing coordinated data collection schedules, which can result in significant performance improvements. We make no assumptions about knowledge of the topology of the network or the capacity available on individual links of the network, i.e., we only use end-to-end information. Finally, we also study the shortcomings of this approach in terms of the gap between the theoretical formulation and the resulting data transfers in wide-area networks. In general, our approach can be used for solving arbitrary data movement problems over the Internet. We use the Bistro platform to illustrate one application of our techniques.