Exploiting Flow Relationships to Improve the Performance of Distributed Applications

Application performance continues to be an issue even with increased Internet bandwidth. There are many reasons for poor application performance including unpredictable network conditions, long round trip times, inadequate transmission mechanisms, or less than optimal application designs. In this work, we propose to exploit flow relationships as a general means to improve Internet application performance. We define a relationship to exist between two flows if the flows exhibit temporal proximity within the same scope, where a scope may either be between two hosts or between two clusters of hosts. Temporal proximity can either be in parallel or near-term sequential. As part of this work, we first observe that flow relationships are plentiful and they can be exploited to improve application performance. Second, we establish a framework on possible techniques to exploit flow relationships. In this framework, we summarize the improvements that can be brought by these techniques into several types and also use a taxonomy to break Internet applications into different categories based on their traffic characteristics and performance concerns. This approach allows us to investigate how a technique helps a group of applications rather than a particular one. Finally, we investigate several specific techniques under the framework and use them to illustrate how flow relationships are exploited to achieve a variety of improvements. We propose and evaluate a list of techniques including piggybacking related domain names, data piggybacking, enhanced TCP ACKs, packet aggregation, and critical packet piggybacking. We use them as examples to show how particular flow relationships can be used to improve applications in different ways such as reducing round trips, providing better quality of information, reducing the total number of packets, and avoiding timeouts. Results show that the technique of piggybacking related domain names can significantly reduce local cache misses and also reduce the same number of domain name messages. The data piggybacking technique can provide packet-efficient throughput in the reverse direction of a TCP connection without sacrificing forward throughput. The enhanced ACK approach provides more detailed and complete information about the state of the forward direction that could be used by a TCP implementation to obtain better throughput under different network conditions. Results for packet aggregation show only a marginal gain of packet savings due to the current traffic patterns. Finally, results for critical packet piggybacking demonstrate a big potential in using related flows to send duplicate copies to protect performance-critical packets from loss

System sizing and resource allocation for video-on-demand systems.

by Mary Y.Y. Leung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.Includes bibliographical references (leaves 64-66).Abstract --- p.iAcknowledgments --- p.iiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Video-On-Demand Environment --- p.1Chapter 1.2 --- Problem Definition --- p.3Chapter 2 --- Related Work --- p.7Chapter 2.1 --- Data Sharing Techniques --- p.7Chapter 2.1.1 --- Batching --- p.7Chapter 2.1.2 --- Buffering --- p.9Chapter 2.1.3 --- Static Partitioning --- p.10Chapter 2.1.4 --- Adaptive Piggybacking --- p.10Chapter 2.2 --- Providing VCR Functionalities --- p.12Chapter 3 --- System Model --- p.15Chapter 3.1 --- Operations involved in VCR Control --- p.15Chapter 3.2 --- Normal Playback Model --- p.17Chapter 3.3 --- VCR Model --- p.18Chapter 4 --- Resource Allocation for Normal Playback --- p.21Chapter 4.1 --- Mathematical Model --- p.22Chapter 4.1.1 --- Hits occurring within the same partition (hit w) --- p.24Chapter 4.1.2 --- Jump to other partitions (hito) --- p.27Chapter 4.1.3 --- Fast-forwarding to the end of a movie --- p.30Chapter 4.1.4 --- The expected hit probability P(hit) --- p.31Chapter 4.2 --- Model Verification --- p.32Chapter 5 --- Resource Allocation for VCR mode --- p.35Chapter 5.1 --- Scheme 1: No merging --- p.36Chapter 5.2 --- Scheme 2: Merging by adaptive piggybacking and buffering --- p.36Chapter 5.2.1 --- Resuming within the threshold (Δ ≤ k) --- p.38Chapter 5.2.2 --- Resuming beyond the threshold (Δ > k) --- p.39Chapter 5.3 --- Verification --- p.42Chapter 6 --- Applications to System sizing --- p.45Chapter 6.1 --- Cost of Resources for Normal Playback --- p.46Chapter 6.2 --- Cost of Resources for VCR functions --- p.48Chapter 6.3 --- Overall system cost --- p.49Chapter 6.4 --- Comparison --- p.50Chapter 6.4.1 --- Scheme 1 vs. Scheme 2 --- p.51Chapter 6.4.2 --- Scheme 2 vs. pure I/O & pure buffer --- p.54Chapter 6.4.3 --- Different values of k --- p.58Chapter 6.4.4 --- Different values of ψ --- p.60Chapter 7 --- Conclusions --- p.62Bibliography --- p.64Chapter A --- Appendix --- p.67Chapter A.l --- Rewind --- p.67Chapter A.1.1 --- Hits occurring within the same partition (hit w) --- p.67Chapter A.1.2 --- Jump to other partitions (hit0) --- p.68Chapter A.2 --- Pause --- p.7

Parallel replication for distributed video-on-demand systems.

Lie, Wai-Kwok Peter.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.Includes bibliographical references (leaves 79-83).Abstract --- p.iAcknowledgments --- p.iiChapter 1 --- Introduction --- p.1Chapter 2 --- Background & Related Work --- p.5Chapter 2.1 --- Early Work on Multimedia Servers --- p.6Chapter 2.2 --- Compression of Multimedia Data --- p.6Chapter 2.3 --- Multimedia File Systems --- p.7Chapter 2.4 --- Scheduling Support for Multimedia Systems --- p.8Chapter 2.5 --- Inter-media Synchronization --- p.9Chapter 2.6 --- Related Work on Replication in VOD Systems --- p.9Chapter 3 --- System Model --- p.12Chapter 4 --- Replication Methodology --- p.15Chapter 4.1 --- Replication Triggering Policy --- p.16Chapter 4.2 --- Source & Target Nodes Selection Policies --- p.17Chapter 4.3 --- Replication Policies --- p.18Chapter 4.3.1 --- Policy 1: Injected Sequential Replication --- p.20Chapter 4.3.2 --- Policy 2: Piggybacked Sequential Replication --- p.22Chapter 4.3.3 --- Policy 3: Injected Parallel Replication --- p.25Chapter 4.3.4 --- Policy 4: Piggybacked Parallel Replication --- p.28Chapter 4.3.5 --- Policy 5: Injected & Piggybacked Parallel Replication --- p.34Chapter 4.3.6 --- Policy 6: Multi-Source Injected & Piggybacked Parallel Replication --- p.36Chapter 4.4 --- Dereplication Policy --- p.37Chapter 5 --- Distributed Architecture for VOD Server --- p.39Chapter 5.1 --- Server Node --- p.40Chapter 5.2 --- Movie Manager --- p.42Chapter 5.3 --- Metadata Manager --- p.42Chapter 5.4 --- Protocols for Distributed VOD Architecture --- p.43Chapter 5.4.1 --- Protocol for Servicing New Customers --- p.43Chapter 5.4.2 --- Protocol for Servicing Existing Customers --- p.45Chapter 5.4.3 --- Protocol for Single/Multi-Source Injected & Parallel Replication --- p.46Chapter 5.4.4 --- Protocol for Dereplication --- p.48Chapter 5.5 --- Failure Handling --- p.49Chapter 5.5.1 --- Handling of Server Node Failures --- p.50Chapter 5.5.2 --- Handling of Movie Manager Failures --- p.52Chapter 6 --- Results --- p.55Chapter 6.1 --- Performance Metric --- p.56Chapter 6.2 --- Simulation Environment --- p.58Chapter 6.3 --- Results of Experiments without Dereplication --- p.59Chapter 6.3.1 --- Comparison of Different Replication Policies --- p.60Chapter 6.3.2 --- Effect of Early Acceptance/Migration --- p.61Chapter 6.3.3 --- Answer to the Resources Consumption Tradeoff issue --- p.62Chapter 6.3.4 --- Effect of Varying Movie Popularity Skewness --- p.64Chapter 6.3.5 --- Effect of Varying Replication Threshold --- p.64Chapter 6.3.6 --- Comparison of Different Target Node Selection Policies --- p.65Chapter 6.4 --- Overall Impact of Dynamic Replication --- p.66Chapter 7 --- Comparison with BSR-based Policy --- p.71Chapter 8 --- Conclusions --- p.75Chapter 8.1 --- Summary --- p.75Chapter 8.2 --- Future Research Directions --- p.76Bibliography --- p.7

Application acceleration for wireless and mobile data networks

This work studies application acceleration for wireless and mobile data networks. The problem of accelerating application can be addressed along multiple dimensions. The first dimension is advanced network protocol design, i.e., optimizing underlying network protocols, particulary transport layer protocol and link layer protocol. Despite advanced network protocol design, in this work we observe that certain application behaviors can fundamentally limit the performance achievable when operating over wireless and mobile data networks. The performance difference is caused by the complex application behaviors of these non-FTP applications. Explicitly dealing with application behaviors can improve application performance for new environments. Along this overcoming application behavior dimension, we accelerate applications by studying specific types of applications including Client-server, Peer-to-peer and Location-based applications. In exploring along this dimension, we identify a set of application behaviors that significantly affect application performance. To accommodate these application behaviors, we firstly extract general design principles that can apply to any applications whenever possible. These design principles can also be integrated into new application designs. We also consider specific applications by applying these design principles and build prototypes to demonstrate the effectiveness of the solutions. In the context of application acceleration, even though all the challenges belong to the two aforementioned dimensions of advanced network protocol design and overcoming application behavior are addressed, application performance can still be limited by the underlying network capability, particularly physical bandwidth. In this work, we study the possibility of speeding up data delivery by eliminating traffic redundancy present in application traffics. Specifically, we first study the traffic redundancy along multiple dimensions using traces obtained from multiple real wireless network deployments. Based on the insights obtained from the analysis, we propose Wireless Memory (WM), a two-ended AP-client solution to effectively exploit traffic redundancy in wireless and mobile environments. Application acceleration can be achieved along two other dimensions: network provision ing and quality of service (QoS). Network provisioning allocates network resources such as physical bandwidth or wireless spectrum, while QoS provides different priority to different applications, users, or data flows. These two dimensions have their respective limitations in the context of application acceleration. In this work, we focus on the two dimensions of overcoming application behavior and Eliminating traffic redundancy to improve application performance. The contribution of this work is as follows. First, we study the problem of application acceleration for wireless and mobile data networks, and we characterize the dimensions along which to address the problem. Second, we identify that application behaviors can significantly affect application performance, and we propose a set of design principles to deal with the behaviors. We also build prototypes to conduct system research. Third, we consider traffic redundancy elimination and propose a wireless memory approach.Ph.D.Committee Chair: Sivakumar, Raghupathy; Committee Member: Ammar, Mostafa; Committee Member: Fekri, Faramarz; Committee Member: Ji, Chuanyi; Committee Member: Ramachandran, Umakishor

Dimensionamento de sistemas de video interativo

Orientador : Nelson Luis Saldanha da FonsecaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Vídeo sob Demanda (VoD) é um serviço que possibilita a exibição de filmes para usuários geograficamente dispersos. Este serviço pode ser utilizado em diversas áreas, tais como entretenimento, bibliotecas digitais e ensino a distância, e através dele, um usuário pode escolher um vídeo dentre uma coleção e ter o vídeo enviado através de uma rede de telecomunicações até sua casa. Um sistema de vídeo interativo deve permitir requisições de operações de VCR a qualquer momento. Estas aplicações requerem uma grande demanda por banda passante. Assim, para o oferecimento destes serviços em larga escala énecessário utilizar técnicas de redução desta demanda. Quando um usuário efetua uma operação de VCR, sua exibição se dessincroniza da exibição do seu grupo, sendo necessário um outro canal de vídeo para dar suporte ao fluxo dessincronizado. Nesta dissertação são avaliados aspectos de desempenho em servidores de sistemas de VoD interativo, nos quais técnicas de compartilhamento de fluxo são empregadas como mecanismo para a redução da demanda de banda passante. Apresenta-se uma nova técnica de dimensionamento do número de canais necessários para se prover a interatividade. Além disso, são introduzidas técnicas para sistemas de VoD com batching, e para sistemas de VoD com batching e piggybackingAbstract: Video-on-demand (VoD) is a service that enables the exhibition offilms for geographically dispersed users. It engenders several application areas such as on-demand movies, digital libraries and distance learning. A video on-demand system which allow VCR operations (true video-on- demand) should grant users' request to perform VCR operations at any time. To reduce the huge bandwidth dernand of VoD, techniques based on multicast have been considered for the deployment of such services in large scale. When a user perforrns a VCR operation, hisjher exhibition unsychronizes with the exhibtion of hisjher multicast group. Therefore, another video channel is needed to support the unsynchronized stream. This thesis introduces a novel dirnensioning technique for channel allocation in interactive VoD systems in order to provide the desired Quality-of-Service. Techniques for VoD systems with batching and for VoD systerns with both batching and piggybacking are presented.MestradoMestre em Ciencia da Informaçã

An Integrated Quality-of-Service Model for Video-on-Demand Application.

The tremendous growth of the Internet paradigm has given rise to Quality of Service (QoS) problems in heterogeneous, ubiquitous, distributed real time applications such as video-on-Demand (VoD). The challenging task in VoD applications is to satisfy diverse client requests for discrete videos with restrained resources by invoking versatile QoS schemes. In this paper, a hybrid QoS strategy, which is a combination of batching and recursive patching is implemented in the local server to ensure starvation-free resource management thereby enhancing the throughput. Batching shares network resources efficiently whereas recursive patching is adopted to reduce the time difference between the requests. The suggested algorithm delivers the complete video to the users based on one of the three communication channels: broadcast, multicast and unicast depending on whether the video is very popular, average popular and least popular respectively. The experimental results show that our strategy accomplishes 35% - 40% reduction in terms of blocking ratio and throughput is 10% - 15% higher than the Poon’s strategy, which guarantees that not only the resources are efficiently utilized but also a suitable Quality of Service is provided to each user

Interactivity And User-heterogeneity In On Demand Broadcast Video

Video-On-Demand (VOD) has appeared as an important technology for many multimedia applications such as news on demand, digital libraries, home entertainment, and distance learning. In its simplest form, delivery of a video stream requires a dedicated channel for each video session. This scheme is very expensive and non-scalable. To preserve server bandwidth, many users can share a channel using multicast. Two types of multicast have been considered. In a non-periodic multicast setting, users make video requests to the server; and it serves them according to some scheduling policy. In a periodic broadcast environment, the server does not wait for service requests. It broadcasts a video cyclically, e.g., a new stream of the same video is started every t seconds. Although, this type of approach does not guarantee true VOD, the worst service latency experienced by any client is less than t seconds. A distinct advantage of this approach is that it can serve a very large community of users using minimal server bandwidth. In VOD System it is desirable to provide the user with the video-cassette-recorder-like (VCR) capabilities such as fast-forwarding a video or jumping to a specific frame. This issue in the broadcast framework is addressed, where each video and its interactive version are broadcast repeatedly on the network. Existing techniques rely on data prefetching as the mechanism to provide this functionality. This approach provides limited usability since the prefetching rate cannot keep up with typical fast-forward speeds. In the same environment, end users might have access to different bandwidth capabilities at different times. Current periodic broadcast schemes, do not take advantage of high-bandwidth capabilities, nor do they adapt to the low-bandwidth limitation of the receivers. A heterogeneous technique is presented that can adapt to a range of receiving bandwidth capability. Given a server bandwidth and a range of different client bandwidths, users employing the proposed technique will choose either to use their full reception bandwidth capability and therefore accessing the video at a very short time, or using part or enough reception bandwidth at the expense of a longer access latency