一个服务器应用管理系统的设计与实现

本文设计实现了一个服务器应用管理系统。通过该系统 ,管理员可以对系统内所有计算机上安装的应用程序进行发布 ,对所有用户的权限进行管理 ;用户可以通过网络远程访问各种应用程序 ;系统自动将各用户请求调度到当前最可用的服务器上 ,优化整个集群的负载分布 ,改善系统性能     

具负载平衡之IPTV影音串流系统

影音媒体具高带宽及实时特性,因此影音串流系统的服务质量的提升端赖影音服务器的有效管理。在此提出一套Video replication及Access request distribution的算法,藉由将热门影音分散到各影音服务器以及影音存取的分散,以达到各影音服务器系统负载平衡的效果。在此比较了3个不同的算法的负载平衡的状况,经实例验证,提出的算法确能达到影音服务器负载平衡的效果,承载更多的系统服务要求。该系统构建在Smart-i TV的IPTV系统台,并讨论了实作的相关技术。     

Dynamic parallel access to replicated content in the Internet

Popular content is frequently replicated in multiple servers or caches in the Internet to offload origin servers and improve end-user experience. However, choosing the best server is a nontrivial task and a bad choice may provide poor end user experience. In contrast to retrieving a file from a single server, we propose a parallel-access scheme where end users access multiple servers at the same time, fetching different portions of that file from different servers and reassembling them locally. The amount of data retrieved from a particular server depends on the resources available at that server or along the path from the user to the server. Faster servers deliver bigger portions of a file while slower servers deliver smaller portions. If the available resources at a server or along the path change during the download of a file, a dynamic parallel access automatically shifts the load from congested locations to less loaded parts (server and links) of the Internet. The end result is that users experience significant speedups and very consistent response times. Moreover, there is no need for complicated server selection algorithms and load is dynamically shared among all servers. The dynamic parallel-access scheme presented does not require any modifications to servers or content and can be easily included in browsers, peer-to-peer applications or content distribution networks to speed up delivery of popular content.     

基于地理信息系统的城市供热信息管理系统的设计与实现

结合设计和开发,介绍了基于地理信息系统的城市供热信息管理系统的整体结构、整体功能、硬件结构。将实时数据、空间拓扑数据、设备属性数据以及对这些数据操作的函数封装为空间实体类,建立了空间实体对象。采用中间件技术,构建了数据图形中间平台,作为整个系统的枢纽将数据、图形与GIS平台,将服务器、工作站有机的联系起来,并对其进行合理的调度。实际运行表明,系统能为供热企业降低成本,提高经济效益。     

Hierarchical packet fair queueing algorithms

We propose to use the idealized hierarchical generalized processor sharing (H-GPS) model to simultaneously support guaranteed real-time, rate-adaptive best-effort, and controlled link-sharing services. We design hierarchical packet fair queueing (H-PFQ) algorithms to approximate H-GPS by using one-level variable-rate PFQ servers as basic building blocks. By computing the system virtual time and per packet virtual start/finish times in unit of bits instead of seconds, most of the PFQ algorithms in the literature can be properly defined as variable-rate servers. We develop techniques to analyze delay and fairness properties of variable-rate and hierarchical PFQ servers. We demonstrate that in order to provide tight delay bounds with an H-PFQ server, it is essential for the one-level PFQ servers to have small worst-case fair indices (WFI). We propose a new PFQ algorithm called WF ²Q+ that is the first to have all the following three properties: (1) providing the tightest delay bound among all PFQ algorithms; (2) having the smallest WFI among all PFQ algorithms; and (3) having a relatively low asymptotic complexity of O(log N). Simulation results are presented to evaluate the delay and link-sharing properties of H-WF²Q+, H-WFQ, H-SFQ, and H-SCFQ     

Cut-through switching, pipelining, and scheduling for networkevacuation

A general model of a virtual circuit network consisting of a number of servers and a number of traffic classes is considered. A traffic class is identified by the sequence of servers that should be visited and the corresponding service rates before a message (customer) of the class leaves the network. The following cases are distinguished: (1) the messages need nonpreemptive service; (2) the service of a message can be preempted at any time; (3) pipelining of the service in a sequence of servers is allowed; and (4) pipelining is not allowed. All of these cases arise in different transmission switching techniques and scheduling schemes. A fluid model that emerges when both preemption and pipelining are allowed is considered. Scheduling schemes in the fluid model are compared with corresponding ones in the network with nonpreemptive service and no pipelining. The problem of evacuating the network from an initial backlog without further arrival is identified in the fluid model. Based on that, a policy with nearly optimal evacuation time is identified for the store-and-forward case. Finally, scheduling with deadlines is considered and it is shown that in the fluid model, the evacuation problem is equivalent to a linear programming problem. The evacuation times under different work-conserving policies are considered in specific examples     

Distributed servers architecture for networked video services

In an on-demand video system, the video repository generally has limited streaming capacities and may be far from the users. In order to achieve higher user capacity and lower network transmission cost, distributed servers architecture can be used, in which multiple local servers are placed close to user pools and, according to their local demands, dynamically cache the contents streamed from the repository. We study a number of caching schemes as applied in the local servers depending on whether the repository is able to multicast movie contents to the local servers or not, and whether the local servers can exchange their cached contents among themselves or not. Our caching schemes keep a circular buffer of data for the movie requested, and hence movies are partially cached. By adjusting the size of the buffer, such caching is able to achieve better tradeoff between network channels and local storage as compared to the traditional caching in which a movie is treated as an entity. For each caching scheme, we study the tradeoff between the local storage and the network channels, and address how the total cost of the system can be minimized by appropriately sizing the buffer. As compared to a number of traditional operations (request batching and multicasting, true-VOD, etc.), we show that distributed servers architecture is able to achieve much lower system cost to offer on-demand video services     

Dynamic ID authentication scheme using chaotic map

Dynamic ID authentication protects user’s identity from being revealed by any outsider during remote login processes. In independent multi-server environments, a user might have to login different servers for accessing various resources. Password based mechanisms are commonly utilized approaches. Without using complicated modular exponentiation computation, in this paper, the author will propose a Chebyshev chaotic map based dynamic ID authentication scheme for independent multi-server environments in which no trusted relationship exists among servers. The proposed scheme does not rely on the existence of registration center and each user only has to keep one single password for accessing resources of different servers. Compared with related protocols, the proposed one has more superior functionalities and lower computational costs. Furthermore, the session key security of our scheme is formally proved in the random oracle model.     

A load scheduler for SIP proxy servers: design,implementation and evaluation of a history weighted window approach

The widespread use of Session Initiation Protocol as a signalling protocol has created various challenges. An important one is that its throughput can be severely degraded when an overload happens in the proxy server because of several retransmissions from the user agent. One common approach to overcome this problem is ‘load balancing’. A balancer needs to know the status of proxy servers, which are continuously gathered implicitly or explicitly. Implicit methods have averagely less overhead than explicit ones. This paper attempts to prevent throughput reduction by balancing the loads among available proxy servers properly using an implicit mechanism called History Weighted Average Response time . The proposed algorithm is robust because it incurs no extra processing to proxy servers. The novelty of the mechanism is making use of ‘response time history’ to estimate the load being currently processed on servers. By implementing in a real testbed, throughput and scalability are improved compared with an important state‐of‐the‐art similar algorithm. This improvement stems from no need for modification in SIP protocol, easy implementation and application, simple computations for making decision and no need for extra feedback between servers and load balancer. Copyright © 2015 John Wiley & Sons, Ltd.     

中小企业部署服务器的方案策略

结合主流厂商小型机和PC服务器现状及产品优缺点的研究，分析了不同类型的小型机服务器和PC服务器体系结构、稳定性能、芯片资源、能耗、成本、适应场景等的差异，提出了中小企业IT平台部署服务器的方案和策略。     

An Efficient Gaming User Oriented Load Balancing Scheme for MMORPGs

Massively multi-player online role-playing games (MMORPGs) follows a client-server model that has the numerous gaming users with many interactions at the same virtual world, massive loading that result in delays, resource shortages, and other such problems occur. Also, faced with high resource demand variability and with misfit resource renting policies, the current practices is to overprovision for each game tens of owned data. Existing load balancing schemes for distributed virtual environments and multiplayer games try to balance the workload among servers by transferring some workload of an overloaded server to other servers. While load balancing algorithms can minimize the average response time of the system, they may also result in frequent client migrations, which may damage the interactivity of an online games. To solve this, many developers devote research to load-balancing servers, yet due to steady and dynamic map divisions, such research is unreliable. Many developers propose algorithms to distribute the load on the server nodes, but the load is usually defined as the number of players on each server, what is not an ideal results. So, we propose a gaming user-oriented load balancing scheme for the load balancing of MMORPGs servers in this paper. This scheme shows effectiveness at dealing with hot-spots and other gatherings of gaming users at specific servers compared to previous methods.     

基于微内核结构的统一网管平台设计研究

微内核结构的软件系统是软件设计发展的方向之一。提出并设计了一套基于微内核结构的统一网管平台。平台采用客户/服务器群模式,服务器端各功能服务器仅负责各业务组件的初始化以及作为调度者充当业务组件与客户端、其他功能服务器之间数据传输的桥梁;具体业务皆由各网管业务组件负责完成。客户端以单一框架为容器,各业务显示、设置部件统一加载、分布其中。同时阐述了网管平台各业务的关键技术实现思想。最后给出了平台运营实例。     

A novel server selection method to achieve delay-based fairness in the server palm

It is pivotal to achieve delay-based fairness when users access the same content, especially in real-time services, from content-replicated servers based upon the client-server communication model. To resolve this issue, this letter proposes a novel server selection method of providing users with delaybased fairness from all the corresponding servers by applying the delay-based dynamic deficit round robin (D3RR) scheme. The deficit counter of the D3RR is adjusted based upon round trip times (RTTs) of data traffic measured by passive-based probing which ensures low resource waste. Performance evaluation results highlight that the delay variance among all the corresponding servers can be maintained as low as possible and delay-based fairness is guaranteed without unnecessary waste of resources.     

一个面向Internet的分布式信息检索系统模型

随着Internet上的用户急剧增加,如何快速地处理查询请求已成为面向Internet的信息检索系统急需解决的问题.文中提出了一个面向Internet的分布式信息检索系统模型(Fastresponse).在该系统模型中,针对当前分布式信息检索系统在可获得性、可靠性、可扩展性、查询服务智能性等方面存在的一些问题,我们提出了对服务器和文档进行两级调度;系统需要时动态招募备份服务器;对子服务器群中和子服务器群间的服务器进行两级监控;根据用户的要求自动重组服务器等一些新的管理策略,有效地解决了上述方面存在的问题,从而可以更好地处理用户的查询请求.     

Generalized Access Structure Congestion System

The k-out-of-n secret sharing schemes are effective, reliable, and secure methods to prevent a secret or secrets from being lost, stolen, or corrupted. The circular sequential k-out-of-n congestion (CSknC) system , based upon this type of secret sharing scheme, is presented for reconstructing secret(s) from any k servers among n servers in circular, sequential order. When a server is connected successfully, it will not be reconnected in later rounds until the CSknC system has k distinct, successfully connected servers. An optimal server arrangement in a CSknC system is determined in where n servers have known network connection probabilities for two states, i.e., congested, and successful. In this paper, we present: i) a generalized access structure congestion (GGammaC) system that is based upon the generalized secret sharing scheme, and ii) an efficient connection procedure for the GGammaC system in terms of the minimal number of server connection attempts. The k-out-of-n secret sharing schemes are considered as simple cases of the generalized secret sharing schemes. It implies that the GGammaC system is a more general system than the CSknC system. We established an iterative connection procedure for the new system. Simulation results are used to demonstrate that the iterative connection procedure is more efficient in terms of minimizing the number of connection attempts     

Load-Balanced Location Management for Cellular Mobile Systems Using Quorums and Dynamic Hashing

This paper presents a new distributed location management strategy for cellular mobile systems. Its salient features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. The proposed strategy does not require a home location register (HLR) to be associated with each mobile node. Location updates and queries for a mobile node are multicast to subsets of location servers, which change with time depending on the location of mobile node/querying node and load on the servers. Simulation experiments demonstrate that such dynamism prevents situations of heavy load on some location servers when mobile nodes are not uniformly distributed in space, or when some mobile nodes have their location updated or queried more often than others. Also, queries return the latest location information of a mobile node with a very high probability. The proposed scheme requires at most one unicast and two rounds of message multicasting for location update and query operations. All multicast messages have a small payload and are restricted to the high bandwidth wired part of the mobile network resulting in low communication overhead. Moreover, if a quorum of location servers gets overloaded, part of its load can be transferred to another lightly loaded quorum using dynamic hashing techniques.     

一种支持同时多线程的VLIW DSP架构

本文提出了一种支持同时多线程的动态分发超长指令字(VLIW)数字信号处理器(DSP)架构。该DSP架构上可以同时运行多个线程,功能单元可以执行来自多个线程的指令,有效地提高DSP的指令吞吐率。为了使多个线程的指令更有效地调度分发到功能单元,该DSP架构还支持指令动态分发,由硬件分发单元而不是编译器来完成多线程指令的动态分配。实验结果表明,相比于单线程而言,本文提出的VLIW DSP架构可以提高功能单元利用率,隐藏存储器访问时延,使处理器的指令吞吐率平均提高约26.89%。     

Hash routing for collections of shared Web caches

Shared Web caches, also referred to as proxy Web servers, allow multiple clients to quickly access a pool of popular Web pages. An organization that provides shared caching to its Web clients will typically have a collection of shared caches rather than just one. For collections of shared caches, it is desirable to coordinate the caches so that all cached pages in the collection are shared among the organization's clients. In this article we investigate two classes of protocols for coordinating a collection of shared caches: the ICP protocol, which has caches ping each other to locate a cached object; and the hash routing protocols, which place objects in the shared caches as a function of the objects' URLs. Our contribution is twofold. First, we compare the performance of the protocols with respect to cache-server overhead and object retrieval latency; for a collection of shared caches, our analysis shows that the hash-routing schemes have significant performance advantages over ICP for both of the performance metrics. The existing hash-routing protocols assume that the cache servers are homogeneous in storage capacity and processing capability, even though most collections of cache servers are vastly heterogeneous. Our second contribution is to extend a robust hash-routing scheme so that it balances requests among the caches according to any desired distribution; the extended hash-routing scheme is robust in the face of cache failures, is tunable for heterogeneous caches, and can have significant performance advantages over ICP     

多媒体调度系统在电力网中的应用

针对电力调度通信视频业务目前的发展状况,介绍了一种多媒体调度系统的方案。阐述了如何利用智能数字调度系统和视频通信系统的结合,为电力调度通信提供了常规语音调度基础之上的视频业务。重点介绍了通过对智能接口的设计、基于视频会议系统中点对点通话、多方会议系统以及基于监控系统的方案实现,达到了多媒体调度系统在电力通信网中的应用。     

Circular sequential k-out-of-n congestion system

A circular sequential k-out-of-n congestion (CSknC) model is presented. This model finds use in reliable systems to prevent single-point failure, such as (k,n) secret key sharing systems. The model assumes that each of the n servers has a known congestion probability. These n servers are arranged in a circle, and are connected sequentially. A server is connected successfully if it is not congested. Previously connected servers are blocked from reconnecting. Congested servers have to be reconnected until k servers are connected successfully. We present the recursive, and marginal formulas for the probability of success, as well as the average number of connection attempts needed with k successfully connected servers. The optimal arrangement of servers is specified to minimize the average number of connection attempts. These formulas can be used to rearrange the servers adaptively when the initial congestion probabilities are not known. Compared to the circular CknG systems, the CSknC systems are shown to have a higher success probability, and require less connection attempts with k successfully connected servers.