传输层网络编码性能分析

底层网络随机丢包导致的传输控制协议(TCP)传输性能恶化的问题由来已久.为了保障TCP的吞吐量在无线网络环境下依然能够保持在较好的性能,通过分析传输层网络编码(TCP/NC)协议的基本原理,分别利用NS-2搭建了软件仿真平台和Wi-Fi开发板搭建了硬件仿真平台.在2种平台上分别测试了传输层网络编码的性能并且分析了TCP的拥塞窗口和吞吐量性能.实验结果表明:传输层网络编码能够有效克服底层的随机丢包带来的影响,提升TCP吞吐量.     

业务流预测在网络编码平台的实现及验证

网络编码由于可以利用无线信道的广播特性带来的空间冗余条件,在无线自组织网络中的应用显示了巨大的潜力。但TCP业务的机会网络编码在无线自组织网络中获得的增益却很小。基于这一问题,提出对TCP业务流具有的自相似性进行FARIMA模型建模,进行数据包到达时间的预测,从而为路由节点根据网络状态进行正确的编码等待决定提供依据,仿真结果验证了TCP业务流的自相似性,预测算法具有良好的预测结果。文中详细介绍了预测算法在COPE网络编码的NS2平台中的具体实现流程。     

无线Mesh网中基于网络编码的多路径TCP研究

在无线多跳网络中,本地重传和网络编码已经被成功地应用到多路径技术上以增加吞吐量并减少丢包。然而,在提高UDP传输性能的同时,也产生了数据包重排序和延迟等副作用,严重影响了TCP性能。针对此问题,主要提出一种基于网络编码的多路径传输方案NC-MPTCP,即在无线mesh网络的多条路径中引入网络编码、执行拥塞控制以及使用一个基于信用的方法控制节点的传输速率,提高网络的吞吐量以及增加网络传输的可靠性。该方案使用一个简单的算法,评估丢包率以及发送线性组合数据包的速率,用来降低目的节点的数据包解码延迟和防止TCP的超时重传。仿真结果表明设计的NC-MPTCP有效。     

无线Mesh网络中跨层协作的路由策略

网络编码可以提高无线Mesh网络的吞吐量,但是网络编码在无线Mesh网络中实际应用获得最大网络利用率是需要解决的问题。提出一种多路径策略,能够通过将网络编码和TCP进行最大化融合提高网络的利用率。网络编码被加入到现有的网络系统,通过解决速率控制问题和分组调度问题,调整源节点的数据编码分块,降低数据包重传的次数,提高网络的吞吐量。     

网络化多媒体实时监控系统的应用研究

采用MPEG－1编码解码国际标准和TCP／IP网络协议,在网络环境下,实现视音频信息和控制数据的网上传输。介绍了网络化多媒体实时监控系统的的构成、工作原理和功能特点,并对视音频实时编码技术和网络编程技术进行了详细探讨。     

网络家电系统原理及设计

随着社会电子化智能程度的深入,基于TCP／IP的网络家电已成为家电系统中极其重要的一部分,在一些发达国家中,TCP／IP网络家电正日益普及并迅速发展。文章结合工作实际从网络家电系统、网络通信技术、网络家电设计等几个方面对网络家电系统原理和设计作了详细分析。     

基于TCP的实时网络视频监控系统的实现

设计并实现了一种基于TCP的实时网络视频监控系统。系统基于海思Hi3515处理器硬件平台,采用TCP网络传输协议,H.264视频压缩编码和DirectDraw图像显示技术,提出了一种视频数据传输I帧处理方法,实现了实时网络视频监控。系统运行结果表明,该系统可以在Internet上实现视频的实时传输,视频显示帧率为16帧/秒(CIF格式),不会出现画面延时、抖动现象,满足了实时网络视频监控的要求。     

TCP over OBS边缘节点重传机制的研究

使用传输控制协议(TCP)的拥塞控制机制在传统互联网技术中是解决问题的很好方法.然而在面对新型的光网络技术OBS网络,简单地采用TCP技术因受到OBS自身特性的影响,性能表现不佳,吞吐量低下.为此,通过对OBS技术和TCP拥塞控制机制深入的研究,提出一种基于OBS边缘节点的ACK重传机制来提升TCP over OBS性能的方法,提高OBS网络吞吐量.     

TCP拥塞控制机制及性能分析

随着因特网的迅猛发展,因特网中的业务量呈逐年上升趋势,研究了TCP拥塞控制机制及其提供的拥塞控制性能,特别是对TCP连接过程中的数据业务流量与丢失率和其他参数的关系进行了深入的研究。分析表明TCP拥塞控制机制可通过控制注入网络的业务流量,在一定程度下缓解网络拥塞程度,但不能实现数据的有效率的传输。     

编码TCP的建模与性能分析

研究了无线网络端到端分组丢失和编码纠错对TCP协议工作过程的影响机制,基于三维Markov链建模描述TCP拥塞窗口和可用窗口的变迁过程,在忽略慢启动阶段的条件下,以最大窗口尺寸、端到端分组丢失率和编码冗余系数为输入参数,通过数值计算求解编码TCP的吞吐率,据此定量分析影响编码TCP性能的因素。基于NS2的模拟实验结果表明基于Markov链的数值计算结果具有较高的准确度。     

Multimedia Networking Improvements of an Embedded System: a Case Study

1 Introduction With the rapid development of the Internet and popu-lar broadband connections to the Internet , more andmore embedded systems are designed with networkingconnections for home and office use[1]. Some examplesof such embedded systems include Wi-Fi cell-phones ,systems for long-distance education,setup boxes for In-ternet TV,and more . These systems typically run anembedded operating system and support TCP/IP net-working on the traditional fast Ethernet and the emerg-ing WLA…     

Storage area network extension solutions and their performance assessment

Several solutions are proposed to extend storage area networking solutions over distances of hundreds to thousands of kilometers. Native fibre channel or end-to-end fibre channel-based solutions can be offered over long distances using SONET-based networks. Protocols such as Internet SCSI (iSCSI), Internet fibre channel protocol (iFCP) and fibre channel over TCP/IP (FCIP) are being proposed to enable storage area networking solutions over networks that use IP as their transport protocol. Performance analysis of these solutions in terms of application throughput under variable network conditions of packet loss, bandwidth availability, extension distance, and TCP implementations in the sender and receiver is presented based on analytical modeling of different solutions.     

利用WinSock实现半导体封装设备的通信

Socket接口是TCP/IP的API,TCP/IP网络中的应用程序,是通过Socket实现的.WinSock是一套开放的、支持多种协议的Windows下的网络编程接口.介绍了利用WinSock进行网络编程的一般方法,并在此基础上解决了半导体封装设备使用TCP/IP协议进行网络实时通信的问题,实现了在服务器和客户机两端准确方便地实时发收文件和互相通信,并测试了发收不同大小文件所消耗的平均时间.     

Mobile IPv6 network: implementation and application

Recently, the world has become increasingly mobile, and people have started communicating by wireless networking. Mobile IPv6 enables mobile users to communicate with each other while moving. In this study, a mobile IPv6 network was implemented by the IEEE 802.11 specification, and its performance was analyzed using TCP and UDP applications. The experimental results indicate that throughput stabilized for UDP applications after about 6–14 seconds. However, TCP applications were found to stabilize throughput in 10–20 seconds. The evaluation results reveal that TCP applications perform less well in mobile IPv6 networking than UDP applications. Copyright © 2006 John Wiley & Sons, Ltd.     

基于IP协议的卫星组网通信关键技术研究

早期卫星组网一般采用地球同步卫星(GEO)作为中继器，而现在的卫星宽带信息网则是通过星间链路(ISL)实现相邻卫星之间直接通信，研究宽带卫星组网技术对于加快我国信息基础设施建设具有极其重要的作用。本首先介绍卫星通过星间链路组网通信的系统模型，然后分析卫星网络IP系统的协议堆栈，并对卫星网络TCP/IP协议各层采用的接口和协议、基本功能、工作方式等进行详细研究，最后对卫星组网通信中涉及的物理层、数据链路层和网络层的关键技术逐一进行了探讨。     

Potential performance bottleneck in Linux TCP

Transmission control protocol (TCP) is the most widely used transport protocol on the Internet today. Over the years, especially recently, due to requirements of high bandwidth transmission, various approaches have been proposed to improve TCP performance. The Linux 2.6 kernel is now preemptible. It can be interrupted mid‐task, making the system more responsive and interactive. However, we have noticed that Linux kernel preemption can interact badly with the performance of the networking subsystem. In this paper, we investigate the performance bottleneck in Linux TCP. We systematically describe the trip of a TCP packet from its ingress into a Linux network end system to its final delivery to the application; we study the performance bottleneck in Linux TCP through mathematical modelling and practical experiments; finally, we propose and test one possible solution to resolve this performance bottleneck in Linux TCP. Copyright © 2007 John Wiley & Sons, Ltd.     

High quality networking of audio-visual information

An overview of low bit rate coding and the interaction between source coding and channel coding is presented. The interaction of coding with networking in a multiuser environment, including algorithms for robust coding which anticipate imperfect network performance, and techniques of decoding a signal that has traversed an imperfect network are described. The performances of such algorithms are illustrated with examples from speech, audio, and video transmission in the presence of packet losses. The challenges in measuring the quality of service (QOS) in the context of new algorithms for coding and networking and the difficulty of measuring QOS in the networking of multimedia information are discussed     

Compensating for moderate effective throughput at the desktop

This article presents the design and development of a networking system architecture targeted to support high-speed TCP/IP communication over ATM. The discussed architecture has been developed in the form of an integrated system which incorporates state-of-the-art software and hardware subsystems, and an OC-12c ATM adapter (622 Mb/s). Moreover, the design of this embedded system has been based on the Chorus real-time operating system, which, in turn, hosts an accelerated TCP/IP protocol stack over ATM. Furthermore, the embedded system board has been developed according to the PCI specification to easily be plugged into a host platform. In addition, the OC-12c ATM adapter subsystem has been designed and developed in order to also be plugged into the same host. The developed architecture has proven very efficient and reliable, providing high-throughput and low-latency bulk data communications. The measured performance on an OC-3c-based (155 Mb/s) testbed has shown that an optimally implemented TCP/IP stack, hosted by a real-time kernel and coupled with an ATM adapter, offers a robust desktop platform for high-speed end-to-end communications. The main feature of the accelerated TCP/IP protocol stack is the out-of-band processing of control and data information. The protocol accelerator embedded system processes the TCP/IP headers and accomplishes checksum computations, while data is transferred from the host's user memory space directly to the network. Finally, for validation purposes, the prototype system has been incorporated in an existing networking infrastructure targeted to support mass storage applications     

基于NIOS Ⅱ的嵌入式以太网口的设计

论述了一种实现嵌入式系统网络化的新思路,通过简化的TCP／IP协议LwIP,利用NIOSⅡ,将其移植到MicroC/OS-Ⅱ操作系统中,以此实现嵌入式设备与网络的互联。从硬件和软件两个部分详细介绍了基于NIOSⅡ软核CPU的嵌入式以太网口的开发。还介绍SOPC Builder的使用,操作系统的移植,TCP／IP的移植以及NIOSⅡ中驱动程序和应用程序的编写。     

Network security via reverse engineering of TCP code: vulnerabilityanalysis and proposed solutions

The Transmission Control Protocol/Internet Protocol (TCP/IP) suite is widely employed to interconnect computing facilities in today's network environments. However, there exist several security vulnerabilities in the TCP specification and additional weaknesses in a number of its implementations. These vulnerabilities may allow an intruder to “attack” TCP-based systems, enabling him/her to “hijack” a TCP connection or cause denial of service to legitimate users. The authors analyze the TCP code via a “reverse engineering” technique called “program slicing” to identify several of these vulnerabilities, especially those that are related to the TCP state-transition diagram. They discuss many of the flaws present in the TCP implementation of many widely used operating systems, such as SUNOS 4.1.3, SVR4, and ULTRIX 4.3. The corresponding TCP attack “signatures” (including the well-known 1994 Christmas Day Mitnick Attack) are described, and recommendations are provided to improve the security state of a TCP-based system (e.g., incorporation of a “timer escape route” from every TCP state). Also, it is anticipated that wide dissemination of this article's results may not only lead to vendor patches to TCP code to plug security holes, but also raise awareness of how program slicing may be used to analyze other networking software and how future designs of TCP and other software can be improved