TCPHA:一个新型的高性能基于内容调度系统

目前Web服务器集群的调度技术中，基于内容的调度是一种主流的调度技术，有很多的优势。但目前流行的基于内容的调度系统普遍存在系统可扩展性差，调度器性能瓶颈问题，而不能充分发挥基于内容调度的优势。该文研究实现了一种新型的基于内容调度系统TCPHA，它在操作系统内核工作，实现了一些最新的技术，如TCP Handoff技术、动态IP Tunnel技术、ARP过滤技术等。性能测试表明，相对于传统的基于内容调度系统，TCPHA有着更高的性能。     

Cuttle：一种新的基于内容的通用调度器

随着互联网迅猛发展，研究Web请求的调度分配技术已成为国内外研究的热点。针对现有Web调度器存在着可扩展性差、系统开销大和无通用性诸多缺陷，设计和实现了一种新 的、通用的、可扩展性好的基于内容的通用调度器Cuttle。该系统在内核TCP／IP层实现，采用伪服务器、捎带技术、截获、伪装三次握手、Mix-LARD调度策略等技术。实验表明，Cuttle的可扩展性好，响应延迟小。     

基于请求包粒度的M:N型TCP switching协议

为了给一种新型Web Cluster系统提出一个优化的实现方案,该文描述了该集群系统的数据流处理过程,分析出其处理实质,即M条TCP连接与N条TCP连接之间动态的交叉衔接问题。为此该文提出了一种基于请求包粒度的M：N型TCP switching协议。详细描述了该协议的设计原理和实现过程。实验证明运行该协议的集群系统具有良好的可扩展性和服务性能。     

基于NDIS的Web邮件监控

本文基于NDIS技术,设计并实现了一个Windows下实时监控发送和接收Web邮件内容的邮件监控系统,提出通过邮件的内在标识ID将多次传输的TCP连接组合成一封邮件,解决了一封邮件分多次TCP传输的难题。实验测试结果表明该系统能准确监控到网络中发送和接收的Web邮件。     

基于TCP协议首部的网络隐蔽通道技术研究

通过研究网络隐蔽通道建立的机制,提出了一种基于TCP协议首部实现网络隐蔽通道的方法,通过将秘密信息经AES加密后嵌入TCP协议首部的序列号和确认号字段,模拟访问Web服务器的行为生成TCP数据包,以达到穿透防火墙和躲避入侵检测系统的目的,并利用此隐蔽通道进行信息传递和远程控制。设计并实现了该原型系统。实验结果表明,该系统的隐蔽性高、传输速度快、可扩展性强,可以实现隐秘信息的传输,也为解决网络隐蔽通道的安全策略问题提供了理论依据和技术支持。     

嵌入式系统Web服务器应用研究开发

介绍了一种嵌入式Web服务器应用系统。该系统借鉴传统服务器系统架构,基于B/S结构模式设计,移植嵌入式TCP/IP协议栈,利用CGI技术以实现客户端和服务器端的动态数据交互。通过本研究可方便实现系统管理、远程终端参数设置等实际应用。     

基于TCP／IP的嵌入式网络电子称量技术研究

基于TCP／IP的嵌入式网络电子称量技术改变了传统电子衡器的操作控制方式，实现了电子衡器的远程控制。本文在分析了基于TCP／IP的嵌入式网络电子称量技术系统结构的基础上，讨论了在电子衡器中嵌入TCP／IP协议栈及Web服务器的具体实现，并阐述了电子衡器的远程控制原理。     

基于嵌入式Web服务器的网络设备测控系统设计

面向Internet是设备网络化设计的发展方向。介绍了互联网在嵌入式设备中的应用，说明了基于嵌入式Web服务器的网络智能设备测控系统的设计方案和软、硬件的实现。硬件上选用Rabbit 2000网络微处理器作为网络接口的Web服务器，构建嵌入式SoC Web服务器，底层软件采用Dynamic C软件开发环境。详细阐述了构建嵌入式Web服务器的具体技术及相关的实现方案，以及实现用TCP、UDP报文进行网络通信、串行口数据通信和对网络智能设备的测控技术等，并给出相关系统软件的程序代码及流程图。目前该系统的运行效果良好。     

嵌入式Web远程监控系统的设计与实现

传统的远程监控系统一般采用C/S模型的方式,针对大型设备,成本高。文章采用SOC芯片C8051F020和10M自适应网络芯片RTL8019AS接口的方案,在单片机中嵌入了精简的TCP/IP协议栈,构建了基于Web的单片机远程监控系统软、硬件平台,在此基础上实现了基于单片机的数据采集和远程监控,所实现的系统具有成本低廉、操作方便、可靠等优点。     

基于嵌入式系统的TCP/IP协议栈的实现

描述了一种可移植的、无须操作系统支持、以软件实现的非路由器TCP／lP原型的实现。该TCP／IP原型基于某种小型嵌入式系统。依据RFC 1122兼容性规定，提供IP、ARP、TCP、UDP服务和Berkeleysocket编程接口。     

业务选择网关的连接模型研究

业务选择网关是随着Internet和网络个性化服务的发展应运而生的。本文通过对基于请求内容分配机制的主要技术之一TCP Handoff技术的分析介绍,提出了一种不同于传统的业务选择网关请求连接和实现的模型。利用TCP handoff技术能将客户请求的响应结果直接返回客户端,消除了由业务选择网关节点而引起的网络通信瓶颈,从而可以显著提高整个服务系统的吞吐率,使整体性能得到极大的改善。     

Content-Aware Playout and Packet Scheduling for Video Streaming Over Wireless Links

Media streaming over wireless links is a challenging problem due to both the unreliable, time-varying nature of the wireless channel and the stringent delivery requirements of media traffic. In this paper, we use joint control of packet scheduling at the transmitter and content-aware playout at the receiver, so as to maximize the quality of media streaming over a wireless link. Our contributions are twofold. First, we formulate and study the problem of joint scheduling and playout control in the framework of Markov decision processes. Second, we propose a novel content-aware adaptive playout control, that takes into account the content of a video sequence, and in particular the motion characteristics of different scenes. We find that the joint scheduling and playout control can significantly improve the quality of the received video, at the expense of only a small amount of playout slowdown. Furthermore, the content-aware adaptive playout places the slowdown preferentially in the low-motion scenes, where its perceived effect is lower.      

基于集群的流媒体缓存代理服务器体系结构

提出了基于集群的流媒体缓存代理服务器体系结构，并将基于内容的前端机负载平衡调度策略引入到流媒体缓存代理服务器的架构设计中，对系统设计原理及各组成模块结构和各模块间的消息通信机制进行了详细的分析阐述，主要采用C和C++语言在Linux操作系统下实现了原型系统，通过对原型系统进行测试，表明整个系统设计合理，性能突出，具有良好的稳定性和可扩展性。     

一种TCP连接的延迟多次迁移技术

现有的基于内容的Web交换技术不能很好地支持HTTP持久连接(P-HTTP)和流水线请求。提出了一种TCP连接的延迟多次迁移方法(DM-TCPHA),前端FE根据第一个请求将连接迁移到选中的BE,该连接上的后续请求报文由BE来调度,且通过强制手段保证BE在收到客户对HTTP回复的确认报文后再执行迁移。该方法具有TCP迁移高性能的优点,且能很好地支持P-HTTP和流水线请求。     

Joint bandwidth allocation,data scheduling and incentives for scalable video streaming over peer-to-peer networks

The overall performance of a peer-to-peer (P2P) scalable streaming system largely depends on the strategies employed in bandwidth allocation, data scheduling and incentives. In this paper, we develop a credit-based content-aware bandwidth auction model for scalable streaming in P2P networks. It formulates multi-overlay multi-layer bandwidth request and allocation problems as auction games. Each peer in the games acts as both auctioneer and player. Being a auctioneer, it maximizes the total revenue (credits) by selling upload bandwidth; Being a player, it uses the credits earned in bandwidth sales to sequentially bid for layer bandwidth so as to maximize the received video quality. Also, a content-aware bidding strategy is proposed, under which the required bandwidth quantity from a peer is determined by the informative video chunks and the marginal net utility that peer could provide, as well as the available credits and the maximum layer bit rate. The convergence of the proposed auction algorithm is mathematically proved. Finally, the performance of the proposed scheme is verified by simulation results.     

Toward balanced and sustainable job scheduling for production supercomputers

Job scheduling on production supercomputers is complicated by diverse demands of system administrators and amorphous characteristics of workloads. Specifically, various scheduling goals such as queuing efficiency and system utilization are usually conflicting and thus need to be balanced. Also, changing workload characteristics often impact the effectiveness of the deployed scheduling policies. Thus it is challenging to design a versatile scheduling policy that is effective in all circumstances. In this paper, we propose a novel job scheduling strategy to balance diverse scheduling goals and mitigate the impact of workload characteristics. First, we introduce metric-aware scheduling, which enables the scheduler to balance competing scheduling goals represented by different metrics such as job waiting time, fairness, and system utilization. Second, we design a scheme to dynamically adjust scheduling policies based on feedback information of monitored metrics at runtime. We evaluate our design using real workloads from supercomputer centers. The results demonstrate that our scheduling mechanism can significantly improve system performance in a balanced, sustainable fashion.     

Architecture of a Web server accelerator

We describe the design, implementation and performance of a high-performance Web server accelerator which runs on an embedded operating system and improves Web server performance by caching data. It can serve Web data at rates an order of magnitude higher than that which would be achieved by a high-performance Web server running on similar hardware under a conventional operating system such as Unix or NT. The superior performance of our system results in part from its highly optimized communications stack. In order to maximize hit rates and maintain updated caches, our accelerator provides an API which allows application programs to explicitly add, delete, and update cached data. The API allows our accelerator to cache dynamic as well as static data. We describe how our accelerator can be scaled to multiple processors to increase performance and availability. The basic design alternatives include a content router or a TCP router (without content routing) in front of a set of Web cache accelerator nodes, with the cache memory distributed across the accelerator nodes. Content-based routing reduces cache node CPU cycles but can make the front-end router a bottleneck. With the TCP router, a request for a cached object may initially be sent to the wrong cache node; this results in larger cache node CPU cycles, but can provide a higher aggregate throughput, because the TCP router becomes a bottleneck at a higher throughput than the content router. We quantify the throughput ranges in which different designs are preferable. We also examine a combination of content-based and TCP routing techniques. In addition, we present statistics from critical deployments of our accelerator for improving performance at highly accessed Sporting and Event Web sites hosted by IBM.     

Preventing TCP performance interference on asymmetric links using ACKs-first variable-size queuing

In developing network-enabled embedded systems, developers are often forced to spend a great deal of time and effort analyzing and solving network performance problems. In this paper, we address one such problem: TCP performance interference on an asymmetric link. The upload or download throughput abruptly degrades if there is simultaneously upload and download TCP traffic on the link. While the problem has been addressed by many researchers, their solutions are incomplete as they only improve throughput in one direction, require TCP protocol modifications in end-user devices or are effective for a limited range of network configurations.In order to overcome such limitations, we propose ACKs-first variable-size queuing (AFVQ) for a gateway. In doing so, we have derived an analytic model of the steady-state TCP performance with bidirectional traffic to clearly identify the two sources of the problem: the excessive queuing delay of ACK packets and the excessive number of ACK packets in the queue. Our AFVQ mechanism is designed to directly eliminate the two causes. Specifically, we have based AFVQ on two policies. First, ACKs-first scheduling is used to shorten the queuing delay of ACK packets. Second, the queue size for ACK packets is dynamically adjusted depending on the number of data packets queued in the gateway so that the number of ACK packets is reduced when packets are congested in the gateway. By applying the two policies simultaneously at the uplink and downlink output queue in the gateway, AFVQ achieves balanced TCP throughput improvements in both directions. In this way, it breaks circular dependencies between upload and download traffic.We have implemented AFVQ in our ADSL-based residential gateway using the traffic control module of the Linux kernel. Our gateway yields 95.2% and 93.8% of the maximum download and upload bandwidth, respectively. We have also evaluated the proposed mechanism using the ns-2 simulator over a wide range of network configurations and have shown that AFVQ achieves better upload and download throughput than other representative gateway-based mechanisms such as ACQ, ACKs-first scheduling and ACK Filtering.