Correction to: Elastic caching solutions for content dissemination services of ip-based internet technologies prospective

Multimedia Tools and Applications - The article title in the original publication of this article contains a mistake.     

Hybrid storage-based caching strategy for content delivery network services

This study proposes a novel caching scheme for content delivery network services. In general, video content users often watch the first part of video clips and then switch to other content. Therefore, a caching scheme is proposed, in which the first part of the frequently referenced content is stored on a solid state drive (SSD) while the remaining video content is stored on a hard disk drive (HDD),. The proposed hybrid (SSD/HDD) caching scheme offers several benefits, such as an improved average data output capacity due to the high average data rate and average hit capacity of the SSD. That is, performance can be significantly improved at a low extra cost with the cache server of a content delivery network (CDN).     

信息中心网络中缓存技术研究综述

因特网中日益增长的内容获取需求促使学术界提出了多种以信息为中心的未来网络架构。这类架构将以主机为中心的通信模式转变为以内容为中心。信息中心网络（ICN）最重要的特征之一是利用内置缓存减少用户获取内容的时延、节省网络带宽和缓解网络拥塞。与传统的内容分发网络（CDN）、对等网络（P2P）和Web缓存系统相比,ICN缓存系统呈现出一系列的新特征。分析了缓存新特征对ICN研究带来的挑战;从多方面重点阐述了ICN缓存的优化方法,详细分析对比了不同缓存策略;指出了未来研究方向并总结全文。     

Collaborative caching for efficient dissemination of personalized video streams in resource constrained environments

The ever increasing deployment of broadband networks and simultaneous proliferation of low-cost video capturing and multimedia-enabled mobile devices such as smart cellular phones, netbook computers, and tablet computers have triggered a wave of novel mobile multimedia applications making video streaming on mobile devices increasingly popular and commonplace. Networked environments consisting of mobile devices tend to be highly heterogeneous in terms of client-side and system-wide resource constraints, clients’ queries for information, geospatial distribution, and dynamic trajectories of the mobile clients, and client-side and server-side privacy and security requirements. Invariably, the video streams need to be personalized to provide a resource-constrained mobile device with video content that is most relevant to the client’s request while simultaneously satisfying the client-side and system-wide resource constraints, privacy and security requirements and the constraints imposed by the geospatial distribution and dynamic trajectories of the mobile clients relative to the server(s). In this paper, we present the design and implementation of a distributed system, consisting of several geographically distributed video personalization servers and proxy caches, for efficient dissemination of personalized video in a resource-constrained mobile environment. With the objective of optimizing cache performance, a novel cache replacement policy and multi-stage client request aggregation strategy, both of which are specifically tailored for personalized video content, are proposed. A novel Latency-Biased Collaborative Caching (LBCC) protocol based on counting Bloom filters is designed for further enhancing the scalability and efficiency of disseminating personalized video content. The benefits and costs associated with collaborative caching for disseminating personalized video content to resource-constrained and geographically distributed clients are analyzed and experimentally verified. The impact of different levels of collaboration among the caches and the advantages of using multiple video personalization servers with varying degrees of mirrored content on the efficiency of personalized video delivery are also studied. Experimental results demonstrate that the proposed collaborative caching scheme, coupled with the proposed personalization-aware cache replacement and client request aggregation strategies, provides a means for efficient dissemination of personalized video streams in resource-constrained environments.     

MSC: a multi-version shared caching for multi-bitrate VoD services

Recently, many Video-on-Demand (VoD) service providers try to attract as many users as possible by offering multi-bitrate video streaming services with differentiated qualities. Many researches focus on video layered coding (e.g., scalable video coding, SVC). However, SVC is not widely used in VoD industry. Another solution, multi-version videos, can be classified into online transcoding and pre-stored multi-version videos. Online transcoding is a CPU-intensive and costly task, so it is not suitable for large-scale VoD applications. In this paper, we study how to improve caching efficiency based on pre-stored multi-version videos. We leverage the sharing probability among different versions of the same video and propose a multi-version shared caching (MSC) method to maximize the benefit of caching proxy. If the desired version is not in the cache while the higher neighbor version is in, MSC transmits the higher version streaming to user temporarily. In this case, MSC can make full use of the caching resources to improve the cache hit ratio and decrease users’ average waiting time. Simulation results show that MSC outperforms the others in the cache hit ratio and the average waiting time.     

An efficient algorithm for partially matched services in internet of services

Internet of Things (IoT) connects billions of devices in an Internet-like structure. Each device encapsulated as a real-world service which provides functionality and exchanges information with other devices. This large-scale information exchange results in new interactions between things and people. Unlike traditional web services, internet of services is highly dynamic and continuously changing due to constant degrade, vanish and possibly reappear of the devices, this opens a new challenge in the process of resource discovery and selection. In response to increasing numbers of services in the discovery and selection process, there is a corresponding increase in number of service consumers and consequent diversity of quality of service (QoS) available. Increase in both sides’ leads to the diversity in the demand and supply of services, which would result in the partial match of the requirements and offers. This paper proposed an IoT service ranking and selection algorithm by considering multiple QoS requirements and allowing partially matched services to be counted as a candidate for the selection process. One of the applications of IoT sensory data that attracts many researchers is transportation especially emergency and accident services which is used as a case study in this paper. Experimental results from real-world services showed that the proposed method achieved significant improvement in the accuracy and performance in the selection process.     

Bailout forward contracts for edge-to-edge internet services

Despite the huge success of the Internet in providing basic communication services, its economic architecture needs to be upgraded so as to provide end-to-end guaranteed or more reliable services to its customers. Currently, a user or an enterprise that needs end-to-end bandwidth guarantees between two arbitrary points in the Internet for a short period of time has no way of expressing its needs. To allow these much needed basic services, we propose a single-domain edge-to-edge (g2g) dynamic capacity contracting mechanism, where a network customer can enter into a bandwidth contract on a g2g path at a future time, at a predetermined price. For practical and economic viability, such forward contracts must involve a bailout option to account for bandwidth becoming unavailable at service delivery time, and must be priced appropriately to enable Internet Service Providers (ISPs) manage risks in their contracting and investments. Our design allows ISPs to advertise point-to-point different prices for each of their g2g paths instead of the current point-to-anywhere prices, allowing discovery of better end-to-end paths, temporal flexibility and efficiency of bandwidth usage. We compute the risk-neutral prices for these g2g bailout forward contracts (BFCs), taking into account correlations between different contracts due to correlated demand patterns and overlapping paths. We apply this multiple g2g BFC framework on network models with Rocketfuel topologies. We evaluate our contracting mechanism in terms of key network performance metrics like fraction of bailouts, revenue earned by the provider, and adaptability to link failures. We also explore the tradeoffs between complexity of pricing and performance benefits of our BFC mechanism.     

非实时服务的SOAP响应缓存策略及其应用

针对企业面向服务体系架构(SOA)环境中非实时服务的重复请求问题,提出一种基于简单对象访问协议(SOAP)扩展的服务响应缓存策略,并在企业服务总线(ESB)上进行了实现,通过将服务响应缓存起来用于应答一定时间内的相同请求,以提高对于这些请求的响应速度。该策略能同时处理普通SOAP响应和带附件SOAP响应,并对SOAP附件设置了防重复缓存机制。在对两个实际服务的测试中,其服务响应时间与采用缓存策略前相比分别缩短了38%和22%,证明了该缓存策略的有效性。     

Evaluation of edge caching/off loading for dynamic content delivery

As dynamic content becomes increasingly dominant, it becomes an important research topic as how the edge resources such as client-side proxies, which are otherwise underutilized for such content, can be put into use. However, it is unclear what will be the best strategy, and the design/deployment trade offs lie therein. In this paper, using one representative e-commerce benchmark, we report our experience of an extensive investigation of different offloading and caching options. Our results point out that, while great benefits can be reached in general, advanced offloading strategies can be overly complex and even counterproductive. In contrast, simple augmentation at proxies to enable fragment caching and page composition achieves most of the benefit without compromising important considerations such as security. We also present proxy+ architecture which supports such capabilities for existing Web applications with minimal reengineering effort.     

基于DHT分布式的物联网发现服务

针对EPCglobal提出的发现服务,在整个供应链中查找物品的信息存在的缺陷,提出了一个基于DHT分布式的发现服务。该方法采用分布式的散列算法为每个参与的节点分配一个标识符,并且每个节点维护一个缓存表用于存储已经查找过的供应链的相关信息,使每个供应链节点都能参与信息的查找,从而消除了中央服务器的概念。通过程序测试对提出的发现服务进行了分析,表明了该方法能够有效地提高网络容量的利用率,解决了负载不平衡等问题。     

PopCap: popularity oriented proxy caching for peer-assisted Internet video-on-demand streaming services

With the success of Internet video-on-demand (VoD) streaming services, the bandwidth required and the financial cost incurred by the host of the video server becoming extremely large. Peer-to-peer (P2P) networks and proxies are two common ways for reducing the server workload. In this paper, we consider a peer-assisted Internet VoD system with proxies deployed at domain gateways. We formally present the video caching problem with the objectives of reducing the video server workload and avoiding inter-domain traffic, and we obtain its optimal solution. Inspired by theoretical analysis, we develop a practical protocol named PopCap for Internet VoD services. Compared with previous work, PopCap does not require additional infrastructure support, is inexpensive, and able to cope well with the characteristic workloads of Internet VoD services. From simulation-based experiments driven by real-world data sets from YouTube, we find that PopCap can effectively reduce the video server workload, therefore provides a superior performance regarding the video server’s traffic reduction.     

面向5G/Beyond 5G的移动边缘缓存优化技术综述

随着移动设备和新兴移动应用的广泛使用,移动网络中流量的指数级增长所引发的网络拥塞、时延较大、用户体验质量差等问题无法满足移动用户的需求。边缘缓存技术通过对网络热点内容的复用,能极大缓解无线网络的传输压力;同时,该技术减少用户请求的网络时延,进而改善用户的网络体验,已经成为面向5G/Beyond 5G的移动边缘计算（MEC）中的关键性技术之一。围绕移动边缘缓存技术,首先介绍了移动边缘缓存的应用场景、主要特性、执行过程和评价指标;其次,对以低时延高能效、低时延高命中率及最大化收益为优化目标的边缘缓存策略进行了分析和对比,并总结出各自的关键研究点;然后,阐述了支持5G的MEC服务器的部署,并在此基础上分析了5G网络中的绿色移动感知缓存策略和5G异构蜂窝网络中的缓存策略;最后,从安全、移动感知缓存、基于强化学习的边缘缓存、基于联邦学习的边缘缓存以及Beyond 5G/6G网络的边缘缓存等几个方面讨论了边缘缓存策略的研究挑战和未来发展方向。     

Design, implementation, and evaluation of differentiated caching services

With the dramatic explosion of online information, the Internet is undergoing a transition from a data communication infrastructure to a global information utility. PDAs, wireless phones, Web-enabled vehicles, modem PCs, and high-end workstations can be viewed as appliances that "plug-in" to this utility for information. The increasing diversity of such appliances calls for an architecture for performance differentiation of information access. The key performance accelerator on the Internet is the caching and content distribution infrastructure. While many research efforts addressed performance differentiation in the network and on Web servers, providing multiple levels of service in the caching system has received much less attention. It has two main contributions. First, we describe, implement, and evaluate an architecture for differentiated content caching services as a key element of the Internet content distribution architecture. Second, we describe a control-theoretical approach that lays well-understood theoretical foundations for resource management to achieve performance differentiation in proxy caches. An experimental study using the Squid proxy cache shows that differentiated caching services provide significantly better performance to the premium content classes.     

移动边缘计算中的无人机三维部署和内容缓存优化方法

随着无线网络中的移动数据流量爆炸式增长,支持高速缓存的无人机被应用于移动计算领域充当边缘服务器,为网络中的用户提供按需服务。为了在满足其他资源约束的条件下,给用户带来更好的体验,通过联合优化无人机部署、缓存放置和用户关联以实现最小化所有用户的内容访问时延,并为用户提供质量不同的内容缓存服务。针对多无人机和地面基站协同提供缓存服务的场景,提出了一种基于迭代优化的联合优化算法。该算法通过迭代求解由目标问题分解得到的三个子问题的方式来获得具有收敛性保证的次优解决方案。首先,采用基于连续凸近似的算法求解无人机部署子问题;其次,采用基于贪心的算法求解内容缓存子问题;然后,利用基于罚函数的连续凸近似算法求解用户关联子问题;最后,对上述过程重复迭代,得到目标问题的一个次优解。多次仿真实验验证了所提算法的有效性和可行性。仿真结果表明,与基准算法相比,所提联合优化算法在平均内容访问时延、缓存命中率两方面均具有更好的性能。     

LinuxDirector: A connection director for scalable internet services

LinuxDirector is a connection director that supports load balancing among multiple Internet servers,which can be used to build scalable Internet services based on clusters of servers.LinuxDirector extends the TCP/IP stack of Linux Kernel to support three IP load balancing techniques,VS/NAT,VS/TUN and VS/DR.Four scheduling algorithms have been implemented to assign connections to different servers.Scalability is achieved by transparently adding or removing a node in the cluster.High availability is provided by detecting node or daemon failure and reconfiguring the system appropriately.This paper describes the design and implementation of LinuxDirector and presents serveral of its features including scalability,high availability and connection affinity.     

A distributed in-network caching scheme for P2P-like content chunk delivery

In-network content caching has recently emerged in the context of information-centric networking (ICN), which allows content objects to be cached at the intermediate router side. In this paper, we specifically focus on in-network caching of peer-to-peer (P2P)-like content objects for improving both service and operation efficiencies. We propose a fully distributed in-network caching protocol for P2P-like content chunks, aiming to reduce P2P based content traffic load and also to achieve improved content distribution performances. Toward this end, the proposed holistic decision-making logic takes into account context information of both the underlying network and the P2P characteristics, such as chunk availability, popularity and peer distances. In addition, we also analyse the benefit of coordination between neighbouring content routers when making caching decisions in order to avoid duplicated P2P chunk caching nearby. An analytical modelling framework is developed to quantitatively evaluate the efficiency of the proposed in-network caching scheme. Extensive experiments are also conducted to validate the analytical results.     

DIMA: Distributed cooperative microservice caching for internet of things in edge computing by deep reinforcement learning

World Wide Web - The ubiquitous Internet of Things (IoTs) devices spawn growing mobile services of applications with computationally-intensive and latency-sensitive features, which increases the...     

Architecture and dependability of large-scale internet services

The popularity of large-scale Internet infrastructure services such as AOL, Google, and Hotmail has grown enormously. The scalability and availability requirements of these services have led to system architectures that diverge significantly from those of traditional systems like desktops, enterprise servers, or databases. Given the need for thousands of nodes, cost necessitates the use of inexpensive personal computers wherever possible, and efficiency often requires customized service software. Likewise, addressing the goal of zero downtime requires human operator involvement and pervasive redundancy within clusters and between globally distributed data centers. Despite these services' success, their architectures-hardware, software, and operational-have developed in an ad hoc manner that few have surveyed or analyzed. Moreover, the public knows little about why these services fail or about the operational practices used in an attempt to keep them running 24/7. As a first step toward formalizing the principles for building highly available and maintainable large-scale Internet services, we are surveying existing services' architectures and dependability. This article describes our observations to date.