一种新型分布式代理缓存系统—双层集群缓存

为了提高代理系统的整体性能,基于内部网络用户访问时间的局部性和相似性,并结合现有的分布式缓存系统,本文提出了一种新型的分布式代理缓存系统——双层缓存集群.双层缓存集群系统分为网内集群缓存层和代理集群缓存层,采用双层代理缓存结构,充分利用现有内部网络资源,分散了代理的负担.降低了代理之间的通信开销,还增强了缓存资源的利用...     

一种针对websearch应用的缓存替换算法

本文通过对websearch负载的分析,总结出负载访问模式的特点,在此基础上提出了一种新的缓存替换算法--ERDP-LRU.与传统的LRU算法的区别是它采用基于重用距离的放置策略.通过模拟实验和实际系统验证,在各种不同的典型负载和缓存大小下,ERDP-LRU的效果均好于其它替换算法.     

一种基于关联规则的代理缓存模型

将数据挖掘中关联规则技术应用到代理缓存管理和调度上，提出了一个新颖的基于关联规则的代理缓存模型，同时对该模型系统实现的一些关键技术做了详细的说明，并初步分析了其性能代价。试验表明该模型具有相当的可行性和有效性。     

流媒体代理缓存技术的研究

随着Internet技术的发展和普遍应用,流媒体技术在Internet上得到了广泛的应用.对流媒体对象的访问,需要高且稳定的传送速率,网络带宽消耗大且持续时间长,容易给其他类型文件的访问带来影响,若用户过多,还会使初始流媒体服务器过载.代理缓存技术可帮助解决上述问题.文中介绍了流媒体代理缓存的特点,流媒体代理缓存的算法,流媒体代理缓存的评价指标和影响流媒体代理缓存效果的因素.     

一种基于LRU算法改进的缓存方案研究与实现

LRU（最近最少使用）替换算法在单处理器结构的许多应用中被广泛使用。然而在多处理器结构中,传统LRU算法对降低共享缓存的缺失率并不是最优的。文中研究了基本的缓存块替换算法,在分析LRU算法的基础上,提出基于LRU算法及访问概率改进的缓存方案,综合考虑最近使用次数和访问频率来决定候选的替换块,增强了替换算法对多处理器的适应性。     

一种基于传输成本的流媒体缓存替换算法及其性能评价

提出一种流媒体缓存替换算法—基于平均传输成本的最小缓存效用算法，并提出一组评价缓存替换算法有效性的性能指标：平均传输成本、中心服务器消耗的带宽和算法的计算开销。模拟结果表明，ATCB-SCU的传输成本和中心服务器消耗的平均带宽都比较低，其计算开销也较低。     

NDN中基于蚁群替换算法的邻居协作缓存管理策略

为提高NDN(命名数据网络)中的缓存利用率,提出了一种基于蚁群替换算法的邻居协作缓存管理(ACNCM)策略。首先将单节点的缓存替换问题,建模为0/1背包问题,并根据缓存数据的大小、使用频率以及邻居副本深度等信息定义本地存储内容的缓存价值,提出基于蚁群算法的缓存替换算法。然后利用邻域协作的思想,通过路由节点之间定期交换自身节点的缓存信息,对单个节点替换出去的缓存内容,选择邻居节点完成协作式缓存管理。实验结果表明,ACNCM策略在缓存命中率、网络开销和平均响应时延方面均优于现有方法。     

一种基于自回归预测的缓存替换算法

由于目前的web缓存替换算法多侧重于对用户的历史访问进行参考,缺乏对用户请求的预测.主要利用自回归模型可用于预测的特性,在基于访问时间间隔(LRU)替换算法的基础之上提出了一种基于自回归模型预测的web缓存替换算法,并进一步的在opnet网络仿真中进行了仿真验证.仿真结果表明:基于自回归预测的缓存替换算法相对于传统的缓存替换算法更能提高代理缓存的对象命中率和字节命中率.     

Web缓存替换算法的研究与改进

缓存替换算法对代理缓存的系统性能起着重要的影响,本文对Web缓存替换算法进行了研究,针对Hybrid算法提出了改进方法。实验结果表明,改进后的算法在保持相对较低的延迟率和较高的URL命中率的情况下,字节命中率有较大的提高,对改善网络状况有一定的意义。     

流媒体代理缓存技术研究

代理缓存是降低流媒体点播系统数据传输代价的一项关键技术,但目前现有的缓存方案,由于受到代理本身缓存空间大小和代理与客户端缺少协作的限制,效率不是很高.针对纯代理缓存系统的不足,文章提出了一种采用代理与客户端缓存协作的方式来弥补以上的不足.通过整合客户端的缓存空间来扩充系统总的缓存空间,依靠代理服务器实现资源的部署与协调.仿真结果显示,对比纯代理缓存系统,由于客户端缓存空间的加入,能显著减少主干网的带宽消耗,降低流媒体数据传输代价.     

Cache Optimization on Hot‐Point Proxy Caching Using Weighted‐Rank Cache Replacement Policy

The development of proxy caching is essential in the area of video‐on‐demand (VoD) to meet users' expectations. VoD requires high bandwidth and creates high traffic due to the nature of media. Many researchers have developed proxy caching models to reduce bandwidth consumption and traffic. Proxy caching keeps part of a media object to meet the viewing expectations of users without delay and provides interactive playback. If the caching is done continuously, the entire cache space will be exhausted at one stage. Hence, the proxy server must apply cache replacement policies to replace existing objects and allocate the cache space for the incoming objects. Researchers have developed many cache replacement policies by considering several parameters, such as recency, access frequency, cost of retrieval, and size of the object. In this paper, the Weighted‐Rank Cache replacement Policy (WRCP) is proposed. This policy uses such parameters as access frequency, aging, and mean access gap ratio and such functions as size and cost of retrieval. The WRCP applies our previously developed proxy caching model, Hot‐Point Proxy, at four levels of replacement, depending on the cache requirement. Simulation results show that the WRCP outperforms our earlier model, the Dual Cache Replacement Policy.     

视频转换编码及其实现技术的研究

转换编码技术是近年来出现的新课题,广泛应用于数字视频通信和多媒体网络中.它是指对已经压缩编码的码流进行再处理,使经过处理后的数据符合传输和接收的要求.本文对转换编码技术的分类和当前的研究进展进行了系统研讨,并进一步指出了它的发展前景.     

变码率视频服务器间隔缓存的接纳策略和替换算法

本文提出了ROC(Resist-Overload Capability)缓存接纳策略和替换算法,解决了使用间隔缓存变码率视频服务器的缓存管理问题.确定性缓存接纳策略能提供确定的服务质量,却存在不适应交互应用和缓存利用率低的缺点;统计复用缓存接纳策略需要海量卷积运算,因此缺乏实用性;ROC缓存接纳策略通过简单运算,提供概率的缓存服务质量保证和较高的缓存利用率.仿真结果表明,在典型系统配置下,ROC缓存接纳策略和替换算法可以提高约25%的系统吞吐量;相对确定性缓存接纳策略和STP-L缓存替换算法,可以多服务约17%的视频流,平均缓存利用率也要高出约38%.     

Cooperative Caching Strategy in Mobile Ad Hoc Networks Based on Clusters

In this paper, we present a scheme, called Cluster Cooperative (CC) for caching in mobile ad hoc networks. In CC scheme, the network topology is partitioned into non-overlapping clusters based on the physical network proximity. For a local cache miss, each client looks for data item in the cluster. If no client inside the cluster has cached the requested item, the request is forwarded to the next client on the routing path towards server. A cache replacement policy, called Least Utility Value with Migration (LUV-Mi) is developed. The LUV-Mi policy is suitable for cooperation in clustered ad hoc environment because it considers the performance of an entire cluster along with the performance of local client. Simulation experiments show that CC caching mechanism achieves significant improvements in cache hit ratio and average query latency in comparison with other caching strategies.     

Improving Web Server Performance with Adaptive Proxy Caching in Soft Real-time Mobile Applications

This paper introduces an adaptive cache proxy to improve the performance of web access in soft real-time applications. It consists of client proxies and cooperative proxy servers with a server-side pushing schema. The large amount of heterogeneous data will be stored in the proxy servers and delivered to clients through computer networks to reduce the response time and network traffic. The adaptive proxy pre-fetches and replaces heterogeneous data dynamically in consideration of networks cost, data size, data change rate, etc. The simulation results show that the modified LUV algorithm has better performance in terms of hit rate, byte hit rate, and delay saving rate. With the cooperative proxy caching, it is shown that the performance of the proxy caching system is more predictable even if the proxies need to deal with a variety of data. The modified adaptive TTL algorithm has better performance in terms of the combination of temporal coherency and system overheads.

大规模连续媒体服务的缓存替换算法设计与实现

连续媒体的缓存设计是非常关键的问题,本文针对大规模连续媒体服务系统的特点,提出了EA缓存替换算法.该算法充分考虑了现有用户和请求接入用户的服务需求,提高了内存使用效率.我们的理论分析和实验模拟证明了它在性能上大大优于传统的缓存替换算法.     

基于媒体用户访问行为偏好模型的代理缓存算法

目前,代理缓存技术广泛应用于改善流媒体传输的服务质量.文章从实际用户日志文件的分析出发,利用发现的用户浏览流媒体对象时的行为分布模型,提出了一种新的视频流媒体缓存算法.仿真结果证明,该算法可以通过记录很少的用户访问信息获取较高的性能表现.     

Proxies + Path Prediction: Improving Web Service Provision in Wireless–Mobile Communications

Mobile computing is considered of major importance to the computing industry for the forthcoming years due to the progress in the wireless communications area. A proxy-based architecture for accelerating Web browsing in wireless customer premises networks is presented. Proxy caches, maintained in base stations, are constantly relocated to follow the roaming user. A cache management scheme is proposed, which involves the relocation of full caches to the most probable cells but also percentages of the caches to less likely neighbors. Relocation is performed according to the output of a user movement prediction algorithm based on a learning automaton. The simulation of the scheme shows considerable benefits for the end user.     

网络多层语义深度挖掘及流媒体缓存策略研究

对网络音视频数据进行多层次语义的深度挖掘,统计分析用户行为,建立一个流行度预测模型,在此基础上提出智能化的代理缓存替换策略.初步模拟实验表明该策略能提高缓存字节命中率,减短客户端的请求延迟时间.     

A unifying co‐operative web caching architecture

Network caching of objects has become a standard way of reducing network traffic and latency in the web. However, web caches exhibit poor performance with a hit rate of about 30%. A solution to improve this hit rate is to have a group of proxies form co‐operation where objects can be cached for later retrieval. A co‐operative cache system includes protocols for hierarchical and transversal caching. The drawback of such a system lies in the resulting network load due to the number of messages that need to be exchanged to locate an object. This paper proposes a new co‐operative web caching architecture, which unifies previous methods of web caching. Performance results shows that the architecture achieve up to 70% co‐operative hit rate and accesses the cached object in at most two hops. Moreover, the architecture is scalable with low traffic and database overhead. Copyright © 2002 John Wiley & Sons, Ltd.