3122979
A dynamic caching algorithm based on internal popularity distribution of streaming media
Most proxy caches for streaming videos do not cache the entire video but only a portion of it. This is partly due to the large size of video objects. Another reason is that the popularity of different parts of a video can be different, e.g., the prefix is generally more popular. Therefore, the development of efficient cache mechanisms requires an understanding of the internal popularity characteristics of streaming videos. This paper has two major contributions. Firstly, we analyze two 6-month long traces of RTSP video requests recorded at different streaming video servers of an entertainment video-on-demand provider, and show that the traces provide evidence that the internal popularity of the majority of the most popular videos obeys a k-transformed Zipf-like distribution. Secondly, we propose a caching algorithm which exploits this empirical internal popularity distribution. We find that this algorithm has similar performance compared with fine-grained caching but requires significantly less state information.
6876063
Popularity-wise proxy caching for interactive streaming media
Most of the current proxy caching algorithms for streaming video media assume that users favor the beginning of the media object. However, this assumption is questionable in highly interactive scenarios, such as e-learning, where some parts of the video other than the prefix can also be popular. A new segment-based proxy caching algorithm, named popularity-wise caching, is proposed for highly interactive streaming. It is designed to deal with arbitrary popularity distribution of media content. Simulations are performed using synthetic traces with different kinds and levels of user interactivity. The results show that the performance of current segment-based caching (such as exponential caching and soccer caching) degrade with increasing user interactivity, while popularity-wise caching can provide the lowest user startup latency for interactive requests and highest bandwidth saving for the backbone network.
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.
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
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.
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.
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.
29521519
Linear Broadcast Routing
Abstract In this paper we examine the problem of performing broadcasts in networks where the messages are constrained to follow linear paths. Many high speed networks, where routing is done in specialized hardware, have this characteristic. We show that the general problem is NP-complete but find a polynomial time approximation algorithm which is guaranteed to provide a solution which is within twice the optimal. We also suggest some generalizations of this work and propose several open problems.
1923772
An energy efficient select optimal neighbor protocol for wireless ad hoc networks
We propose two location-aware select optimal neighbor (SON) algorithms that are suitable for CSMA/CA based MAC protocols for wireless ad hoc networks. Both algorithms optimize the energy efficiency by reducing the effective number of neighbors and thus reduce the transmission power as well as the overhearing power consumption at irrelevant receivers. NS-2 simulations show that our algorithms can achieve about 28% and 38% average energy savings per node compared to CSMA/CA based MAC protocols such as IEEE 802.11.
17395638
A Simple Method for Parameterized Verification of Cache Coherence Protocols
We present a simple method for verifying the safety properties of cache coherence protocols with arbitrarily many nodes. Our presentation begins with two examples. The first example describes in intuitive terms how the German protocol with arbitrarily many nodes can be verified using a combination of Murphi model checking and apparently circular reasoning. The second example outlines a similar proof of the FLASH protocol. These are followed by a simple theory based on the classical notion of simulation proofs that justifies the apparently circular reasoning. We conclude the paper by discussing what remains to be done and by comparing our method with other approaches to the parameterized verification of cache coherence protocols, such as compositional model checking, machine-assisted theorem proving, predicate ion, invisible invariants, and cut-off theorems.