Performance analysis of Energy Efficient Ethernet on video streaming servers

Current trends on traffic growth oversee a steady increase of video streaming services, and the subsequent development of the associated infrastructure to allocate and distribute such contents. One of the operational costs associated to this infrastructure is the power bill. Therefore any mechanism used to decrease it, reducing also the carbon footprint associated to it, is welcome. In this work we investigate the suitability of the recently standardized IEEE 802.3az Energy Efficient Ethernet (EEE) for video traffic generated by video-streaming servers. The conclusion of the analysis is positive about the achievable energy savings, due to the inherent features of traffic patterns of video-streaming servers which help reducing the number of transitions between active and low-power modes in EEE.     

Throughput optimization for video streaming proxy servers based on video staging

A video streaming proxy server needs to handle hundreds of simultaneous connections between media servers and clients. Inside, every video arrived at the server and delivered from it follows a specific arrival and delivery schedule. While arrival schedules compete for incoming network bandwidth, delivery schedules compete for outgoing network bandwidth. As a result, a proxy server has to provide sufficient buffer and disk cache for storage, together with memory space, disk space and disk bandwidth. In order to optimize the throughput, a proxy server has to govern the usage of these resources. In this paper, we first analyze the property of a traditional smoothing algorithm and a video staging algorithm. Then we develop, based on the smoothing algorithm, a video staging algorithm for video streaming proxy servers. This algorithm allows us to devise an arrival schedule based on the delivery schedule. Under this arrival and delivery schedule pair, we can achieve a better resource utilization rate gracefully between different parameter sets. It is also interesting to note that the usage of the resources such as network bandwidth, disk bandwidth and memory space becomes interchangeable. It provides the basis for inter-resource scheduling to further improve the throughput of a video streaming proxy server system.

Research on scheduling algorithms in Web cluster servers

This paper analyzes quantitatively the impact of the load balance scheduling algorithms and the locality scheduling algorithms on the performance of Web cluster servers,and brings forward the Adaptive_LARD algorithm.Compared with the representative LARD algorithm,the advantages of the Adaptive_LARD are that:(1)it adjusts load distribution among the back-ends through the idea of load balancing to avoid learning steps in the LARD algorithm and reinforce its adaptability;(2)by distinguishing between TCP connections accessing disks and those accessing cache memory,it can estimate the impact of different connections on the back-ends‘load more precisely.Performance evaluations suggest that the proposed method outperforms the LARD algorithm by up to 14.7%.     

Proxy-assisted periodic broadcast for video streaming with multiple servers

Large scale video streaming over the Internet requires a large amount of resources such as server I/O bandwidth and network bandwidth. A number of video delivery techniques can be used to lower these requirements. Periodic broadcast by a central server combined with proxy caching offers a significant reduction of the aggregate network and server I/O bandwidth usage. However, the resources available to a single server are still limited. In this paper we propose a system with multiple geographically distributed servers. The problem of multiple servers for periodic broadcast is quite different from the problem of object location for multiple web servers. Multiple servers offer increased amount of resources and service availability and may potentially allow a further reduction of network bandwidth usage. On the other hand, the benefit of periodic broadcast mostly comes from high demand videos. With multiple servers holding a video, the demand of the video at each server is reduced. Therefore, it is a challenge to use multiple servers efficiently. We first analyze the dependence of the resource requirements on the number and locations of the servers. Based on the character of the function describing such a dependence, we formulate and solve the problem of video location and delivery, in a way that minimizes resource usage. We explore a trade-off between network and I/O bandwidth requirements. We evaluate our proposed solutions through a number of tests.

Efficient admission control algorithms for multimedia servers

In this paper, we have proposed efficient admission control algorithms for multimedia storage servers that are providers of variable-bit-rate media streams. The proposed schemes are based on a slicing technique and use aggressive methods for admission control. We have developed two types of admission control schemes: Future-Max (FM) and Interval Estimation (IE). The FM algorithm uses the maximum bandwidth requirement of the future to estimate the bandwidth requirement. The IE algorithm defines a class of admission control schemes that use a combination of the maximum and average bandwidths within each interval to estimate the bandwidth requirement of the interval. The performance evaluations done through simulations show that the server utilization is improved by using the FM and IE algorithms. Furthermore, the quality of service is also improved by using the FM and IE algorithms. Several results depicting the trade-off between the implementation complexity, the desired accuracy, the number of accepted requests, and the quality of service are presented.     

Video placement and configuration of distributed video servers on cable TV networks

A large-scale, distributed video-on-demand (VOD) system allows geographically dispersed residential and business users to access video services, such as movies and other multimedia programs or documents on demand from video servers on a high-speed network. In this paper, we first demonstrate through analysis and simulation the need for a hierarchical architecture for the VOD distribution network.We then assume a hierarchical architecture, which fits the existing tree topology used in today's cable TV (CATV) hybrid fiber/coaxial (HFC) distribution networks. We develop a model for the video program placement, configuration, and performance evaluation of such systems. Our approach takes into account the user behavior, the fact that the user requests are transmitted over a shared channel before reaching the video server containing the requested program, the fact that the input/output (I/O) capacity of the video servers is the costlier resource, and finally the communication cost. In addition, our model employs batching of user requests at the video servers. We study the effect of batching on the performance of the video servers and on the quality of service (QoS) delivered to the user, and we contribute dynamic batching policies which improve server utilization, user QoS, and lower the servers' cost. The evaluation is based on an extensive analytical and simulation study.     

Approximate algorithms for document placement in distributed Web servers

We study approximate algorithms for placing a set of documents into M distributed Web servers in this paper. We define the load of a server to be the summation of loads induced by all documents stored. The size of a server is defined in a similar manner. We propose five algorithms. Algorithm 1 balances the loads and sizes of the servers by limiting the loads to k/sub l/ and the sizes to k/sub s/ times their optimal values, where 1/k/sub l/-1 + 1/k/sub n/-1. This result improves the bounds on load and size of servers in (L.C. Chen et al., 2001). Algorithm 2 further reduces the load bound on each server by using partial document replication, and algorithm 3 by sorting. Algorithm 4 employs both partial replication and sorting. Last, without using sorting and replication, we give algorithm 5 for the dynamic placement at the cost of a factor Q(log M) in the time-complexity.     

Efficient support for interactive operations in multi-resolution video servers

In this paper, we present a placement algorithm that interleaves multi-resolution video streams on a disk array and enables a video server to efficiently support playback of these streams at different resolution levels. We then combine this placement algorithm with a scalable compression technique to efficiently support interactive scan operations (i.e., fast-forward and rewind). We present an analytical model for evaluating the impact of the scan operations on the performance of disk-arr ay-based servers. Our experiments demonstrate that: (1) employing our placement algorithm substantially reduces seek and rotational latency overhead during playback, and (2) exploiting the characteristics of video streams and human perceptual tolerances enables a server to support interactive scan operations without any additional overhead.     

Efficient support for interactive browsing operations in clusteredCBR video servers

Providing efficient support for interactive browsing operations such as fast-forward (ff) and fast-backward (fb) is essential in video-on-demand and other multimedia server systems. In this paper, we propose two basic approaches to scheduling interactive browsing operations: 1) the prefetching approach and 2) the grouping approach. Block-skipping and frame-skipping algorithms are presented for constant bit rate (CBR) data blocks. These algorithms can precisely schedule video streams for both normal play and interactive browsing operations     

基于流媒体服务器集群副本放置策略的研究

网络流媒体服务具有数据流量大、服务时间长的特点,同时,高并发的服务请求会造成流媒体服务质量明显下降等性能瓶颈问题。针对这种现象,设计了一种基于Zipf分布规律的两阶段副本放置策略,并成功应用于某市中小学心理辅导的视讯平台。实践结果表明,与传统的方法相比,该方法具有较好的实用值和健壮性。     

Efficient programming paradigm for video streaming processing on TILE64 platform

Advances at an unprecedented rate in computer hardware and networking technologies have made the many-core computing affordable and readily available in a matter of few years. Nonetheless, it incurs challenges to programmers to build scalable parallel software. Optimizations of parallel programs for a many-core platform are viewed as a multifaceted problem, where system and architectural factors should be taken into account. In this paper, we tackle this problem by implementing parallel programs with different available programming paradigms and evaluate application behaviors on TILE64 many-core platform. That is, we investigate a hybrid producer-write plus consumer-read shared memory programming paradigm for the implementation of master–worker video decoder and encoder in the referred many-core platform. Experimental results show that the proposed implementation has achieved competitive performance speedup, scaling well with the number of available cores and up to four times of performance improvement over other implementations on the decoding of sample 1080P video.     

ZipfAllocation: an algorithm for static allocation of movies in a cluster of video servers

When a single video server provides a streaming service, there are many limitations. Thus, clusters of multiple video servers are widely used today to provide better service. How movies are allocated to each server in a cluster is an important and ongoing research topic because the movies are large, and there are so many of them. We have developed a movie allocation algorithm based on the observation that client accesses follow a Zipf distribution. We have developed an algorithm in which servers use their storage to their full capacities, movies are assigned to servers as evenly as possible, servers receive requests as evenly as possible, and all movies are allocated to at least one server. Copyright © 2010 John Wiley & Sons, Ltd.     

直播服务器一般性框架体系设计

基于流媒体服务器设计框架,结合直播服务器本身的功能、特性,并综合考虑波动的网络环境对其的影响,给出一种适用于直播服务器的一般性的实现框架。在这个实现框架中直播服务器由四个功能模块组成:速率控制模块、差错控制模块、质量自适应模块以及缓冲区控制模块。这四个功能模块各自完成特定的功能,并相互协作以使直播服务器系统作为整体提供适应性的视频传输服务。对各功能模块之间的协作和互动关系作了详细的阐述。提出的框架体系可以根据应用需求进行灵活配置以得到适当的实现形式,对开发直播系统具有参考价值。     

Design a progressive video caching policy for video proxy servers

Proxy servers have been used to cache web objects to alleviate the load of the web servers and to reduce network congestion on the Internet. In this paper, a central video server is connected to a proxy server via wide area networks (WANs) and the proxy server can reach many clients via local area networks (LANs). We assume a video can be either entirely or partially cached in the proxy to reduce WAN bandwidth consumption. Since the storage space and the sustained disk I/O bandwidth are limited resources in the proxy, how to efficiently utilize these resources to maximize the WAN bandwidth reduction is an important issue. We design a progressive video caching policy in which each video can be cached at several levels corresponding to cached data sizes and required WAN bandwidths. For a video, the proxy server determines to cache a smaller amount of data at a lower level or to gradually accumulate more data to reach a higher level. The proposed progressive caching policy allows the proxy to adjust caching amount for each video based on its resource condition and the user access pattern. We investigate the scenarios in which the access pattern is priorly known or unknown and the effectiveness of the caching policy is evaluated.     

Performability of disk-array-based video servers

Video services are likely to dominate the traffic in future broadband networks. Most of these services will be provided by large- scale public-access video servers. Research to date has shown that disk arrays are a promising technology for providing the storage and throughput required to serve many independent video streams to a large customer population. Large disk arrays, however, are susceptible to disk failures which can greatly affect their reliability. In this paper, we discuss suitable redundancy mechanisms to increase the reliability of disk arrays and compare the performance of the RAID-3 and RAID-5 redundancy schemes. We use cost and performability analyses to rigorously compare the two schemes over a variety of conditions. Accurate cost models are developed and Markov reward models (with time-dependent reward structures) are developed and used to give insight into the tradeoffs between system cost and revenue earning potential. The paper concludes that for large-scale video servers, coarse-grained striping in a RAID-5 style of disk array is most cost effective.     

流媒体服务器比例带宽分配的改进算法

结合比例带宽分配与转码技术,提出了基于转码的流媒体服务器比例带宽分配算法.该算法将服务器分配与调度资源的过程细分为一系列充分小的时间片,在每一个时间片里,服务器根据已有的资源分配与预测的带宽需求情况进行综合分析,动态地给每一个请求分配带宽.建立的数学模型表明了该策略能保证所有请求都能在不同的负载下获得最佳的带宽分配.仿真实验结果表明,该策略不仅可以充分利用系统资源,而且还能保证不同优先级请求之间资源的公平分配.     

Efficient algorithms for single- and two-layer linear placement of parallel graphs

This paper outlines an algorithm for optimum linear ordering (OLO) of a weighted parallel graph with O(n log k) worst-case time complexity, and O(n + k log(n/k) log k) expected-case time complexity, where n is the total number of nodes and k is the number of chains in the parallel graph. Next, the two-layer OLO problem is considered, where the goal is to place the nodes linearly in two routing layers minimizing the total wire length. The two-layer problem is shown to subsume the maxcut problem and a befitting heuristic algorithm is proposed. Experimental results on randomly generated samples show that the heuristic algorithm runs very fast and outputs optimum solutions in more than 90% instances.     

Construction algorithms and approximation bounds for the streaming cache placement problem in multicast networks

The streaming cache placement problem (SCPP) is considered. The SCPP is known to be NP-hard and MAX SNP-hard. It is shown that for the SCPP there is no approximation algorithm with a guarantee better than log k unless NP can be solved in sub-exponential time. Construction algorithms for the SCPP, based on two general techniques, are proposed. The results of computational experiments based on these two algorithms and their modifications are reported. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 124–137, November–December 2005.     

A stepwise optimization algorithm of clustered streaming media servers

The optimization of Clustered Streaming Media Servers (CSMS), which aims at using as few hardware resources and as cost-effective as possible, while providing satisfactory performance and QoS, has a great impact on the practicability and efficiency of CSMS. Based on the analysis and formulization of critical performance factors of CSMS and the relationship among the performance, QoS, and the costs in CSMS, a stepwise optimization algorithm is developed to solve the optimization problem efficiently. The algorithm is based on an approach that models the optimization problem into a directed acyclic graph and then addresses the complex optimization problem step by step. The algorithm applies a divide and conquer model that not only reduces the complexity of the optimization problem, but also accelerates the optimization process. Progressive information is collected in the process and used in solving the problem. Furthermore, a simulation system of CSMS is necessary for the optimization algorithm to generate the accurate information produced in the entire streaming service process. Thus, we designed and implemented such a simulation system based on the theoretical performance model of CSMS and the parameters measured in practical CSMS testbed. Finally, a case study of the optimization problem is given to demonstrate the process of the algorithm, and an appropriate plan for designing practical CSMS system is illustrated.