高速长距离网络传输协议

传统的TCP传输协议在高速长距离网络中存在许多局限,其传输性能不能满足日益增长的海量数据传输应用的需求.UDP传输协议尽管传输速率很高,却没有可靠性保证.分析了传统的传输协议在高速长距离网络中的局限,分类总结了近年来提出的各种改进的传输协议的主要设计思想以及在传输协议性能评价方面的工作,最后提出了目前研究中仍然存在的开放性问题和进一步的研究方向.     

高速长距离光网络传输协议性能分析

随着光网络技术、IP与光融合等技术的发展,互联网领域出现了高速长距离光网络.中美俄环球科教网络(GLORIAD)是个典型的高速长距离光网络.在基于GLORIAD的测量和实验中,发现带宽利用率存在瓶颈,通过进一步分析高速长距离光网络的特点和传输协议TCP的机制,发现了以TCP协议机制为主的影响传输性能的原因.文章对此进行了比较全面的分析和阐述,并提出了TCP协议改进思路和进一步研究方向.     

面向城域应用的混合式无线网络设计与评测

针对传统城域视频会议中利用有线骨干网连接各无线局域网(WLAN)的方案不能满足按需灵活组网和覆盖城市周边欠发达地区以及远郊的需求,提出了结合WLAN本地覆盖和基于定向天线实现长距离传输的混合式无线网络架构,通过网络性能实测和视频会议应用系统的实际运行,验证了该网络架构的可行性.在测试的基础上,分析了长距离传输网络中基于TDMA的媒体访问控制(MAC)协议设计以及混合式无线网络中面向本地覆盖和长距离传输的两类MAC协议之间的协同等方面的重要性.     

高速长距离网络传输性能优化

从传输协议和网络节点两方面分析高速长距离网络传输性能的影响因素,介绍中间节点拥塞避免、减少主机负载以及改进传输协议等各种性能优化方法,并结合仿真和实际网络实验验证,指出各种技术的优缺点。对传输性能优化技术进行总结并给出设计终端性能自适应的传输协议。     

终端性能自适应传输协议

随着各种应用的需求和光网络技术的飞速发展,互联网领域出现了高速长距离光网络.最新研究发现,由于当前各种科学应用的迫切需求以及网络带宽的迅速提高,网络速率已经远远超出了终端系统的处理能力.在高速长距离光网络环境中,拥塞已经从网络转移到了终端,终端系统的处理能力逐渐成为传输速率的瓶颈.因此,各种终端性能自适应的高速传输协议应运而生.基于这一类协议改进的不同思路,对它们进行了分类描述,重点分析了这些协议的拥塞检测和速率适配机制以及各自的优缺点,在归纳和总结目前研究中仍然存在的开放性问题的同时,提出了进一步的研究方向.     

终端性能自适应传输协议

随着各种应用的需求和光网络技术的飞速发展,互联网领域出现了高速长距离光网络.最新研究发现,由于当前各种科学应用的迫切需求以及网络带宽的迅速提高,网络速率已经远远超出了终端系统的处理能力.在高速长距离光网络环境中,拥塞已经从网络转移到了终端,终端系统的处理能力逐渐成为传输速率的瓶颈.因此,各种终端性能自适应的高速传输协议应运而生.基于这一类协议改进的不同思路,对它们进行了分类描述,重点分析了这些协议的拥塞检测和速率适配机制以及各自的优缺点,在归纳和总结目前研究中仍然存在的开放性问题的同时,提出了进一步的研究方向.     

关于高速长距离光网络传输性能的分析

本文从整体上对高速长距离光网络传输性能进行了分析。首先就高速长距离光网络传输的特点进行了介绍,然后对其传输性能做出了探讨。     

一种改进HSTCP公平性的拥塞控制算法

标准传输控制协议在高速、长距离等应用条件下存在网络带宽不能充分利用的问题, 高速传输协议的提出可以解决此问题, 但在数据包往返时延上存在较大不公平性. 在分析传输公平性基础上, 通过离散事件网络模拟器进行公平性模拟验证, 提出一种通过添加公平因子改进高速传输协议公平性的算法, 经仿真验证, 该算法减轻了因RTT不同造成的不公平性.     

高速网络TCP改进协议NS2仿真性能比较

传统TCP协议在现代高速网络中传输性能存在瓶颈。基于NS2,通过改变瓶颈带宽、往返时延及TCP并行流数等参数,仿真实验了各种TCP改进协议的传输性能,在吞吐率、时延和丢包率等性能指标上对各种协议进行比较。结果表明,多数改进协议在某些方面表现出比传统TCP协议更好的性能,其中采用显式拥塞反馈改进方案的XCP和VCP协议性能表现最好。     

基于UDP的可靠数据传输协议仿真研究

传统TCP协议在现代高速网络中的数据传输变的低效,具有不同往返时延的TCP数据流在竞争瓶颈带宽时将引发带宽不公平分配问题.基于UDP的可靠数据传输协议(UDP-based Data Transfer Protocol, UDT)是在UDP之上增加了可靠性和拥塞控制机制,适合于高速网络下的大量数据传输,具有很高的公平性.通过NS2仿真平台,改变瓶颈带宽、时延等形成不同的网络环境,在效率、公平、稳定等UDT目标性能上同传统TCP进行比较研究,结果显示UDT在高速网络环境下具有比传统TCP更优的传输性能.     

Wireless Sensor Network transport protocol: A critical review

The transport protocols for Wireless Sensor Network (WSN) play vital role in achieving the high performance together with longevity of the network. The researchers are continuously contributing in developing new transport layer protocols based on different principles and architectures enabling different combinations of technical features. The uniqueness of each new protocol more or less lies in these functional features, which can be commonly classified based on their proficiencies in fulfilling congestion control, reliability support, and prioritization. The performance of these protocols has been evaluated using dissimilar set of experimental/simulation parameters, thus there is no well defined benchmark for experimental/simulation settings. The researchers working in this area have to compare the performance of the new protocol with the existing protocols to prove that new protocol is better. However, one of the major challenges faced by the researchers is investigating the performance of all the existing protocols, which have been tested in different simulation environments. This leads the significance of having a well-defined benchmark for the experimental/simulation settings. If the future researchers simulate their protocols according to a standard set of simulation/experimental settings, the performance of those protocols can be directly compared with each other just using the published simulation results. This article offers a twofold contribution to support researchers working in the area of WSN transport protocol design. First, we extensively review the technical features of existing transport protocols and suggest a generic framework for a WSN transport protocol, which offers a strong groundwork for the new researchers to identify the open research issues. Second we analyse the experimental settings, focused application areas and the addressed performance criteria of existing protocols; thus suggest a benchmark of experimental/simulation settings for evaluating prospective transport protocols.     

通信协议的并行机制研究

通信技术的迅速发展，通信网络所提供的带宽达到几百Ｍｂｐｓ～Ｇｂｐｓ数量级。一些应用，象多媒体通信，就能利用网络的高吞吐量。但是，目前的通信协议并不能适应高速传输的环境。运输层和其它较高层协议的处理，已成为通信系统的性能瓶颈。本文首先回顾近十年来通信环境所发生的一些变化，并分析其对运输层协议的影响；第二部分分析标准协议并行实现时的一些关键技术；最后介绍了一个运输层系统模型，该模型采用并行机制，向上提供高性能的运输层服务。     

Simulation methodology and performance analysis of network coding based transport protocol in wireless big data networks

The Multi-Path, Multi-Hop (MPMH) communications have been extensively used in wireless network. It is especially suitable to big data transmissions due to its high throughput. To provide congestion and end-to-end reliability control, two types of transport layer protocols have been proposed in the literature: the TCP-based protocols and the rateless coding based protocols. However, the former is too conservative to explore the capacity of the MPMH networks, and the latter is too aggressive in filling up the communication capacity and performs poorly when dealing with congestions. To overcome their drawbacks, a novel network coding scheme, namely, Adjustable Batching Coding (ABC), was proposed by us, which uses redundancy coding to overcome random loss and uses retransmissions and window size shrink to relieve congestion. The stratified congestion control strategy makes the ABC scheme especially suitable for big data transmissions. However, there is no simulation platform built so far that can accurately test the performance of the network coding based transport protocols. We have built a modular, easy-to-customize simulation system based on an event-based programming method, which can simulate the ABC-based MPMH transport layer behaviors. Using the proposed simulator, the optimal parameters of the protocol can be fine-tuned, and the performance is superior to other transport layer protocols under the same settings. Furthermore, the proposed simulation methodology can be easily extended to other variants of MPMH communication systems by adjusting the ABC parameters.     

主动结点启动的可靠多播通信

一、概述在Internet网上实现多播通信还存在没有完全解决的技术问题,如反馈信息爆炸、丢失数据局部恢复功能等,针对这些问题目前有两个主要研究方向:定时器方法(如SRM)和等级结构化方法(如RMTP),但它们都只能部分地解决这些问题。     

Protocol Customization for Improving MPI Performance on RDMA-Enabled Clusters

Optimizing Message Passing Interface (MPI) point-to-point communication for large messages is of paramount importance since most communications in MPI applications are performed by such operations. Remote Direct Memory Access (RDMA) allows one-sided data transfer and provides great flexibility in the design of efficient communication protocols for large messages. However, achieving high point-to-point communication performance on RDMA-enabled clusters is challenging due to both the complexity in communication protocols and the impact of the protocol invocation scenario on the performance of a given protocol. In this work, we analyze existing protocols and show that they are not ideal in many situations, and propose to use protocol customization, that is, different protocols for different situations to improve MPI performance. More specifically, by leveraging the RDMA capability, we develop a set of protocols that can provide high performance for all protocol invocation scenarios. Armed with this set of protocols that can collectively achieve high performance in all situations, we demonstrate the potential of protocol customization by developing a trace-driven toolkit that allows the appropriate protocol to be selected for each communication in an MPI application to maximize performance. We evaluate the performance of the proposed techniques using micro-benchmarks and application benchmarks. The results indicate that protocol customization can out-perform traditional communication schemes by a large degree in many situations.     

广域网中RPC应用加速网关的研究与实现

通过分析时延和带宽对传输控制协议和应用协议性能的影响,得出广域网的高时延是造成广域网数据传输速率低下的主要原因,尤其对应用层中请求-响应式协议影响更为明显。针对此问题设计基于应用代理的加速方案,并且实现基于RPC协议的应用加速。实验数据表明这种基于应用代理的加速方法对请求-响应式应用层协议的网络传输性能有良好的加速效果。     

无线传感器网络能量多路径路由研究

研究了无线传感器分层网络模型及能量多路径路由机制．为解决现有协议的缺陷，提出了改进型能量多路径路由协议(IMP-EA)，建立了路由算法．以网络寿命和丢包率作为评价指标，对改进型能量多路径路由协议和其它3种路由协议进行了仿真实验．仿真结果表明，改进后的协议有效地延长了网络的生存时间，提高了数据转发效率．     

Is it really good to talk? Testing the impact of providing concurrent verbal protocols on driving performance

Abstract

Questions have been raised regarding the impact that providing concurrent verbal protocols has on task performance in various settings; however, there has been little empirical testing of this in road transport. The aim of this study was to examine the impact of providing concurrent verbal protocols on driving performance. Participants drove an instrumented vehicle around a set route, twice whilst providing a concurrent verbal protocol, and twice without. A comparison revealed no differences in behaviour related to speed, braking and steering wheel angle when driving mid-block, but a significant difference in aspects of braking and acceleration at roundabouts. When not providing a verbal protocol, participants were found to brake harder on approach to a roundabout and accelerate more heavily coming out of roundabouts. It is concluded that providing verbal protocols may have a positive effect on braking and accelerating. Practical implications related to driver training and future research are discussed.

Practitioner Summary: Verbal protocol analysis is used by ergonomists to understand aspects of cognition and decision-making during complex tasks such as driving and control room operation. This study examines the impact that it has on driving performance, providing evidence to support its continued use in ergonomics applications.