流媒体技术(5) 第五章 流媒体的传输与控制协议

第一节流媒体传输和控制协议概述1.流媒体基础网络协议为: TCP、UDP(传输层) IP协议(互联网层) 2.传输协议为: (1)RTP、RTCP RTP为实时传输协议,通过UDP协议传输。RTCP为实时传输控制协议,可以通过TCP协议传输,也可以通过UDP协议传输,但与RTP采用不同的端口号,加以分离。     

一种长延时信道的加密IP数据加速方法

长延时信道传输TCP/IP数据受信道时延特性影响,分组传输速度由延时决定,而不取决于信道速率,造成信道速率越高传输效率越低下的问题。采用IP协议加速器可以有效提高卫星信道传输速率,进而提高卫星信道利用效率。但是,加密IP数据将传输层数据作为一个整体进行处理,传统的加速方法无法适用于这种数据的加速传输。将经过加密的传输层数据作为一个整体,重新封装成标准TCP或UDP格式,使用相应的加速策略,判断加速与否,采用相应加速方法,加速数据传输,从而解决加密IP数据的加速问题。     

QUIC协议研究

为了解决当前TCP传输存在的两个主要问题:(1)建立连接、断开连接的耗时传输机制;(2)前序包阻塞(Head-of-line blocking,HOL)问题,本文介绍一种基于UDP作为底层传输的全新协议(Quick UDP Internet Connections,QUIC),通过采用UDP为传输层协议,避免建立连接、断开连接的耗时问题和前序包阻塞问题,并且通过一种巧妙的机制保证可靠性传输,克服UDP传输存在的问题.     

基于GPRS的远程监控系统设计

针对当前输油管道压力监控现状,结合GPRS通信模块MC39i,给出了能够实现远程数据传输并可广泛应用于远程监控系统的设计方案.重点阐述了系统的硬件组成以及基于嵌入式实时操作系统FreeRTOS实现数据传输模块的软件设计;采用基于状态机的结构设计方法实现PPP链路层协议,实现GPRS模块与互连网络的连接;分析和比较了UDP和TCP两种传输层数据传输方式,并给出了基于uIP TCP/IP协议栈实现TCP和UDP传输协议的原理;对UDP协议的传输可靠性进行改进,采用带握手的UDP协议可以较好地满足实时性的可靠性要求,并对数据传输性能进行了测试.     

基于网络模拟的自组网路由协议分析

Ad Hoe网络是无须中心设施的无线网络,网络节点依靠自身寻找路由,这使得路由协议得到更多关注.为了考察传输层协议对路由性能的影响,文章在研究Ad Hoc网络典型路由协议工作原理的基础上,利用NS2网络仿真软件,分析了它们在UDP、TCP两种传输层协议下的性能变化.结果表明,采用UDP协议时,AODV总体性能对DSDV优势明显,而使用TCP协议时,AODV的性能略逊于DSDV.     

基于GPRS的远程监控系统设计

针对当前输油管道压力监控现状,结合GPRS通信模块MC39i,给出了能够实现远程数据传输并可广泛应用于远程监控系统的设计方案。重点阐述了系统的硬件组成以及基于嵌入式实时操作系统FreeRTOS实现数据传输模块的软件设计;采用基于状态机的结构设计方法实现PPP链路层协议,实现GPRS模块与互连网络的连接;分析和比较了UDP和TCP两种传输层数据传输方式,并给出了基于uIP TCP/IP协议栈实现TCP和UDP传输协议的原理;对UDP协议的传输可靠性进行改进,采用带握手的UDP协议可以较好地满足实时性的可靠性要求,并对数据传输性能进行了测试。     

基于GPRS的远程监控系统设计

针对当前输油管道压力监控现状，结合GPRS通信模块MC39i，给出了能够实现远程数据传输并可广泛应用于远程监控系统的设计方案。重点阐述了系统的硬件组成以及基于嵌入式实时操作系统FreeRTOS实现数据传输模块的软件设计；采用基于状态机的结构设计方法实现PPP链路层协议，实现GPRS模块与互连网络的连接；分析和比较了UDP和TCP两种传输层数据传输方式，并给出了基于uIP TCP/IP协议栈实现TCP和UDP传输协议的原理；对UDP协议的传输可靠性进行改进，采用带握手的UDP协议可以较好地满足实时性的可靠性要求，并对数据传输性能进行了测试。     

流媒体技术(5)

第五章流媒体的传输与控制协议 第一节流媒体传输和控制协议概述 1.流媒体基础网络协议为: TCP、UDP(传输层) IP协议(互联网层) 2.传输协议为:     

关于上Internet网和TCP/IP协议的实用技术

越来越多的嵌入式应用增加了Internet网络功能,但是,嵌入式应用的编程人员对于上网和TCP／IP协议比较生疏,由于需要了解的技术内容很多,因此很难短时间从中找出有用的关键部分,本文打算对新手给以实用性的指导。TCP／P包括一系列协议首先,应理解我们所说的TCP／IP是统指一系列的协议,其中包括TCP（传输控制协议）、UDP（用户数据报协议）、IP（Internet协议）,还有一些更低层的连接层协议,如Ethernet（以太网协议）等。用TCP协议传输的所谓数据实际指的是数据流中的段,而用UDP协议传输的所谓数据指的是数据包。IP则…     

基于可靠UDP的卫星IP网关设计

TCP是面向连接的可靠点到点协议,但是由于卫星网络中典型的长延时、高误码率以及非对称带宽的特点,导致TCP通过宽带卫星网络时,信道利用率非常低。可靠UDP协议基于标准UDP协议并在应用中增加窗口、应答和重传算法来实现。网关采用该协议将TCP连接分段,在应用中明显地改善了TCP在宽带卫星信道上传输的性能,增加TCP的信道利用率。     

DHTTP: an efficient and cache-friendly transfer protocol for the web

Today's HTTP carries Web interactions over client-initiated TCP connections. An important implication of using this transport method is that interception caches in the network violate the end-to-end principle of the Internet, which severely limits deployment options of these caches. Furthermore, while an increasing number of Web interactions are short, and in fact frequently carry only control information and no data, TCP is often inefficient for short interactions We propose a new transfer protocol for the Web, called Dual-Transport HTTP (DHTTP), which splits the traffic between UDP and TCP channels. When choosing the TCP channel, it is the server who opens the connection back to the client. Through server-initiated connections, DHTTP upholds the Internet end-to-end principle in the presence of interception caches, thereby allowing unrestricted caching within backbones. Moreover, the comparative performance study of DHTTP and HTTP using trace-driven simulation as well as testing real HTTP and DHTTP servers showed a significant performance advantage of DHTTP when the bottleneck is at the server and comparable performance when the bottleneck is in the network.     

一种安全隧道网关的设计与实现

针对应用层客户/服务器系统安全性欠缺的情况,设计、实现了一套基于SSL/TLS协议的安全隧道网关,以提供无缝的安全集成.客户端隧道网关与服务器端隧道网关之间基于X.509证书进行身份认证,并建立SSL/TLS安全链接转发客户端请求与服务器端响应.隧道网关与客户端、服务器之间采用普通TCP/IP链接进行数据传输.隧道网关使已有客户/服务器系统无需任何修改即可享有机密性、完整性和可认证的数据传输.最后给出了网关测试结果与应用实例.     

基于TCP／IP硬件栈的新型服务器结构

随着大数据时代的到来,基于通用处理器的服务器由于硬件结构的限制,很难在提高性能的同时降低功耗,现提出了一种基于TCP／IP硬件栈的新型服务器架构,将TCP／IP处理流程从通用CPU中分离出来,采用专门的硬件电路实现,在性能与通用服务器相同的情况下,大幅度降低功耗。最后使用FPGA搭建了原型机,并与IBM通用服务器进行了对比测试。     

Proposing a standardized protocol for raw biosignal transmission

In this paper, we propose a standardized interface called TiA (TOBI interface A) to transmit raw biosignals, supporting multirate and block-oriented transmission of different kinds of signals from various acquisition devices (e.g., EEG, electrooculogram, near-infrared spectroscopy signals, etc.) at the same time. To facilitate a distinction between those kinds of signals, so-called signal types are introduced. TiA is a single-server, multiple-client system, whereby clients can connect to the server at runtime. Information transfer between client and server is divided into control and data connections. The control connections use transmission control protocol (TCP) and transmit extensible-markup-language (XML)-encoded meta information. The data transmission utilizes a user datagram protocol (UDP) or TCP with a binary data stream. A standardized handshaking procedure for the connection setup and a standardized binary data packet has been defined. Thus, a standardized layer, abstracting used hardware devices and facilitating distributed raw data transmission in a standardized way, has been evolved. A cross-platform library, implemented in C ++, is available for download.     

Transport protocols for Internet-compatible satellite networks

We address the question of how well end-to-end transport connections perform in a satellite environment composed of one or more satellites in geostationary orbit (GEO) or low-altitude Earth orbit (LEO), in which the connection may traverse a portion of the wired Internet. We first summarize the various ways in which latency and asymmetry can impair the performance of the Internet's transmission control protocol (TCP), and discuss extensions to standard TCP that alleviate some of these performance problems. Through analysis, simulation, and experiments, we quantify the performance of state-of-the-art TCP implementations in a satellite environment. A key part of the experimental method is the use of traffic models empirically derived from Internet traffic traces. We identify those TCP implementations that can be expected to perform reasonably well, and those that can suffer serious performance degradation. An important result is that, even with the best satellite-optimized TCP implementations, moderate levels of congestion in the wide-area Internet can seriously degrade performance for satellite connections. For scenarios in which TCP performance is poor, we investigate the potential improvement of using a satellite gateway, proxy, or Web cache to “split” transport connections in a manner transparent to end users. Finally, we describe a new transport protocol for use internally within a satellite network or as part of a split connection. This protocol, which we call the satellite transport protocol (STP), is optimized for challenging network impairments such as high latency, asymmetry, and high error rates. Among its chief benefits are up to an order of magnitude reduction in the bandwidth used in the reverse path, as compared to standard TCP, when conducting large file transfers. This is a particularly important attribute for the kind of asymmetric connectivity likely to dominate satellite-based Internet access     

基于4G网络的视频加密传输系统设计

设计了一种视频加密传输设备,利用HDMI或USB接口接收外部摄像机或DV机视频数据流,对视频流数据进行编码,再经过加密处理后,通过4G移动网络将加密压缩的视频流数据传送至服务端。当服务器远端有设备连接时,能接收并播放视频数据。该传输设备软件实现了视频采集编码、4G移动网络、数据加密、TCP/IP协议传输数据等模块,与远端服务器通过私有协议发送加密数据,验证了各模块的工作性能以及可靠性。     

基于以太网的远程数据采集系统设计

针对远程数据采集方面的应用需求,设计了一种基于ARM微处理器的以太网数据采集系统。选取S3C2440作为数据处理器和控制器,DM9000作为网络芯片,在Linux为操作平台下,实现了10位数据采集,并将采集到的数据经过S3C2440的处理,通过以太网传输到服务器上。数据传输采用的网络通信协议是TCP/IP协议,通信过程采用C/S模式。     

TCP/IP协议处理器的多连接管理设计与实现

介绍了一种基于TCP/IP协议的可支持数千条连接的网络处理器,主要对TCP协议处理模块的多连接管理和切换做了重点的阐述.TCP协议是面向连接的协议,以往多连接的实现是将每一个连接作为操作系统的一个进程,由操作系统的进程管理程序统一进行调度.当需要将多连接用硬件来实现时,连接的切换就需要仿照操作系统的进程调度机制来进行.提出的多连接管理和切换的机制已经用Verilog HDL描述,并在Xilinx的Vertex4开发版上得到验证,结果证明此多连接管理和切换机制可以很好地支持数千条连接的同时运行,并在新型网络处理器中得到应用.     

Suitability of DAMA and Contention-Based Satellite Access Schemes for TCP Traffic in Mobile DVB-RCS

The problem of optimizing access and bandwidth sharing among transmission control protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type.     

Throughput Analysis and Measurements in IEEE 802.11 WLANs with TCP and UDP Traffic Flows

There is a vast literature on the throughput analysis of the IEEE 802.11 media access control (MAC) protocol. However, very little has been done on investigating the interplay between the collision avoidance mechanisms of the 802.11 MAC protocol and the dynamics of upper layer transport protocols. In this paper, we tackle this issue from an analytical, simulative, and experimental perspective. Specifically, we develop Markov chain models to compute the distribution of the number of active stations in an 802.11 wireless local area network (WLAN) when long-lived transmission control protocol (TCP) connections compete with finite-load user datagram protocol (UDP) flows. By embedding these distributions in the MAC protocol modeling, we derive approximate but accurate expressions of the TCP and UDP throughput. We validate the model accuracy through performance tests carried out in a real WLAN for a wide range of configurations. Our analytical model and the supporting experimental outcomes show that 1) the total TCP throughput is basically independent of the number of open TCP connections and the aggregate TCP traffic can be equivalently modeled as two saturated flows; and 2) in the saturated regime, n UDP flows obtain about n times the aggregate throughput achieved by the TCP flows, which is independent of the overall number of persistent TCP connections.