Transport Protocols in the TCP Paradigm and their Performance

This paper defines a class of “TCP-like” transport protocols, called protocols in the TCP Paradigm. The name indicates the protocols are not TCP, but in some sense similar to it. The class includes TCP and also Tom Kelly's “Scalable TCP”, and more. Most of the protocols in the class require ECN in order to become implementable. Most even require a form of ECN that allows a high rate of marked packets. The paper analyzes performance of protocols in the TCP Paradigm and indicates a subset that is likely to perform as well as, or quite possibly better than, Scalable TCP. Criteria are the ability to achieve high throughput, to maintain a steady flow if the ECN marking probability is constant, and to adapt quickly to a changing marking probability. A main conclusion is that in order to benefit from protocols in this paradigm, “source behavior” (reaction of endpoints to marked and unmarked packets) and “router behavior” (how routers choose marking probabilities) must be investigated together.     

面向卫星网络的TCP传输性能的研究

卫星信道的长时延、高误码率、大延时带宽积等的特性使TCP协议的性能受到了很大的影响.为了提高卫星网络下TCP的性能,在不破坏TCP端到端语义的前提下,文中利用在异构网络的边界处设置具有传输控制功能的性能增强代理(Performance Enhancing Proxies,PEP)的理论模型,在SACK TCP协议下对该模型实现了一种卫星网络的拥塞控制和拥塞恢复策略.仿真实验表明,新模型能够充分利用卫星网络的带宽,达到获得最佳有效吞吐量的目的.     

Analysis of TCP Performance over Mobile Ad Hoc Networks

Mobile ad hoc networks have attracted attention lately as a means of providing continuous network connectivity to mobile computing devices regardless of physical location. Recent research has focused primarily on the routing protocols needed in such an environment. In this paper, we investigate the effects that link breakage due to mobility has on TCP performance. Through simulation, we show that TCP throughput drops significantly when nodes move, due to TCP's inability to recognize the difference between link failure and congestion. We also analyze specific examples, such as a situation where throughput is zero for a particular connection. We introduce a new metric, expected throughput, for the comparison of throughput in multi-hop networks, and then use this metric to show how the use of explicit link failure notification (ELFN) techniques can significantly improve TCP performance.     

数字电视前端综合监控系统的实施

安全播出作为广电系统的生命线,在当今数字电视技术高速发展,业务日趋丰富的背景下,高效、全面、严密的监测手段和监控系统对于数字电视播出前端而言显得尤其重要。从传输流与信道监测系统、多画面显示监测录像报警系统、卫星节目安全监控系统三个方面探讨数字电视前端监控。     

A Simulation Study of Scalable TCP and HighSpeed TCP in Geostationary Satellite Networks

This paper investigates the performance of two TCP enhancements (i.e., Scalable TCP and HighSpeed TCP), recently proposed for high-speed backbone networks with a very large bandwidth-delay product, in a geostationary satellite environment. Both persistent and elastic traffic patterns are considered, performance being evaluated in terms of TCP throughput and mean session delay, respectively. The impact of channel characteristics (packet error rate, correlation between successive losses) is widely discussed. Fairness issues are also accounted for, together with the impact of some system parameters, such as the satellite link bandwidth. Extensive comparisons are carried out among Scalable TCP, HighSpeed TCP and other congestion control schemes. The obtained results show the soundness for the use of such protocols in geostationary satellite networks. Indeed, both protocols permit to improve the performance of TCP connections in a wide range of channel conditions, showing (especially Scalable TCP) to be able to cope well with rainy conditions and to exploit a future increase in the satellite link capacity. This work was carried out within the framework of the SatNex Network of Excellence, http://www.satnex.org     

适应卫星IP网络的安全解决方案研究

卫星IP网络作为地面IP网络的延伸,其固有的信道特性带来了TCP性能问题和安全问题。目前业界提出的主流安全解决方案不能很好地适应TCP性能增强技术。文中通过对主流安全解决方案和TCP性能增强技术进行深入研究,挖掘二者不能良好适应的原因,最后提出一种新的适应卫星IP网络的安全解决方案。     

A Receiver-Driven Transport Protocol for the Web

In this paper, we present a receiver-oriented, request/response protocol for the Web that is compatible with the dynamics of TCP's congestion control algorithm. The protocol, called WebTP, is designed to be completely receiver-based in terms of transport initiation, flow-control and congestion-control. We propose a dual window-cum-rate based congestion control mechanism that is compatible with parallel TCP flows, and in fact interacts better with a congested network state. In support of our receiver-driven design, we developed a novel retransmission scheme that is robust to delay variations. The resulting flows achieve efficient network utilization and are qualitatively fair in their interaction amongst themselves and even with competing TCP flows. The paper also provides detailed simulation results to support the protocol design.     

卫星IP网络中传输控制协议的研究

传输控制协议(TCP)是TCP / IP协议栈的主要传输协议,它在网络中的传输效率是影响IP网络传输性能的关键因素之一。当网络中存在卫星链路时,卫星链路的一些固有特性会使TCP的传输性能受到一定影响。文中首先指出卫星信道的特点,对TCP协议在卫星网络中的传输性能进行了分析,重点介绍最近几年这方面的研究成果。