Parlay网关中SIP服务器状态机的设计与实现

在Parlay网关实现SIP协议的映射过程中，SIP服务器的设计是关键。为了确保映射的消息传递机制可靠以及呼叫标识唯一，文章对SIP协议适配器进行了详细的设计，并针对oSIP协议栈中的状态机，在SIP协议适配器中设计了对应的状态机迁移方法和相应的回调函数，最后给出了SIP协议适配器中设计的类图。     

oSIP协议栈的研究及应用

针对GNU oSIP协议栈进行了深入研究,讨论了oSIP协议栈的结构功能及其核心的状态机模块.在研究和实践的基础上,介绍了如何在POSIX兼容系统中实现基于oSIP的SIP应用,最后给出了基于oSIP的应用模型,通过实验测试,该模型工作得非常稳定.     

基于OMAP5912和SIP的IP电话终端

以车载汽车电子多媒体视听系统为研发背景，在OMAP5912平台上采用SIP（会话发起协议）设计了IP电话终端。详细说明了IP电话终端的主要硬件组成部分，介绍了SIP和oSIP协议栈，给出了嵌入式系统IP电话软件的程序设计框架和效果，并对在该基础上实现无线IP电话终端提出了进一步的设想。     

NGN集中监测系统SIP解码模块的设计与实现

介绍了NGN集中测试系统中SIP解码模块的概念及功能,监测功能包括消息数据解析、核心参数提取、利用关键参数进行呼叫合成以及对合成结果进行统计分析处理四个环节,其中消息的解析又包含了消息数据详细解析与合成信息数据提取解析两个部分。基于RFC3261详细说明了SIP消息数据结构,研究了SIP解码方案,对比其他SIP协议解析系统,在编程中采用了逐行提取解析的方法,最终获得某些重要呼叫相关参数,从而为进一步实现呼叫CDR合成以及统计等高级监测功能提供了参考数据。通过现场实测验证了相关理论算法的可行性,同时保证了SIP监测系统的稳定性。     

基于SIP协议的会议软电话设计

随着现代社会人与人之间沟通交流需求的日益迫切,基于SIP协议在网络IP电话得以迅速发展与广泛应用。本文提出了一种基于SIP协议会议软电话的设计实现方案,该方案是基于Windows平台,用C＋＋编写。其呼叫控制模块采用SIP协议,开源的oSIP/eXosip协议栈实现,语音视频模块分别采用流行通用的G.729和H.263编码方案,结合三者开发出SIP软件可视电话的应用程序,其会议模式亦可方便进行三方通话。经测试表明,该软件可视电话具有良好的通话质量和视频效果。最后,本文对该会议电话做了一些功能和性能上的展望。     

基于Netfilter的深度包检测SIP防火墙的设计

针对传统包过滤防火墙不适用于SIP会话这一情况,采用深度包检测技术,设计了一个基于Netfilter的深度包检测SIP防火墙。此防火墙能够实施有状态的SIP感知,深度检查SIP消息,并且动态生成媒体流传输通道,达到SIP会话安全防护能力。     

基于STB和SIP视频通信软件设计及测试

本文中的视频呼叫控制协议选用SIP协议,通信数据的传输承载于NGB网络。设计了总体软件流程,包括STB与SIP终端之间的通信流程,视频播放浏览器模块与视频通信模块之间的接口函数。最后搭建模拟测试平台,对所构成的视频通信模块进行了测试;同时利用Wireshark1.6.1抓包软件,抓取SIP协议数据包,验证了SIP协议能够正常工作,可应用于简易的视频通信。     

SIP软电话在嵌入式手持终端的设计与实现

SIP是原生支持移动性的协议,具有简单性、扩展性、伸缩性等特点,是嵌入式移动终端的理想信令协议。在嵌入式手持终端上实现基于SIP的软电话,该系统由SIP协议进行信令控制,并可进行多媒体会话。文章详细描述了嵌入式软件开发流程,介绍了oSIP2协议栈的调用方法、Linux下多线程编写技术、MiniGUI形界面编程特点以及调试过程。     

基于ARM和DSP的VoIP网关的设计与实现

文章介绍了基于ARM和DSP的VoIP网关的软硬件设计.其中硬件主要由基于ARM内核的微处理器S3C44B0子系统和基于LSI403LP芯片的DSP子系统以及电话接口模块构成.软件设计主要负责控制SIP核心协议栈oSIP、RTP/RTCP核心协议栈ccRTP的正常运转,控制外围DSP芯片工作.测试证明,文章所设计的VoIP网关能够实现网关的主要功能,具有成本低廉、应用灵活、可扩展性好的特点.     

P2P检测控制系统中的协议分析

线速采集全部数据包，进行协议分析和业务类型识别，是实现P2P检测控制系统的基础。本文主要介绍P2P检测控制系统中协议分析的方法和流程，包括数据链路层到传输层的基本报文解析和应用层的协议识别，为各种P2P业务检测系统和网管系统提供参考。     

Selective parsing to enhance SIP performance

The session initiation protocol (SIP) is used as the signaling protocol in the IP multimedia subsystem (IMS) and the signaling is becoming computing intensive comparing to the current telecommunication network. The SIP is a text-based protocol with characteristics of unordered and verbose headers, variable-size message, and case-insensitive keyword. It imposes challenges for an efficient message processing. The property of SIP elements being able to process SIP messages quickly is critical for the performance of IMS networks. This article investigates the performance of SIP message processed in SIP servers, mainly focusing on improving message parsing by introducing a method named selective parsing for SIP message (SP4SIP). By modeling and analyzing a SIP server with a tandem Jackson network, it is concluded that parsing messages is the bottleneck of a SIP server performance, i.e., it is the most processing intensive activity in the system. To validate the approach, it has been implemented in a high-performance SIP server in the authors' lab. The results show that selective parsing for SIP message can indeed reduce processing time.     

一种SIP协议栈中呼叫过程的设计与实现

随着VoIP技术的飞速发展,SIP协议正日益受到业界的重视,越来越多地应用于3G网络。本文提出并基于C语言编程实现一种完全自主设计的SIP协议栈,包括消息编解码模块、状态机模块、传输层模块。实现用户代理客户端和用户代理服务器间的工作状态调度,进而使得两个用户代理能够进行多媒体会话。     

Improved variations relating the Ziv-Lempel and Welch-typealgorithms for sequential data compression

Several data compression algorithms relating existing important source coding algorithms, including Ziv-Lempel codes, Rissanen's Context, and Welch's LZW method, are presented. First, an intermediate algorithm between the two Ziv-Lempel methods for universal data compression is proposed, which has the same asymptotic optimality as the well-known method based on the incremental parsing. The proposed algorithm is then compared with the context gathering algorithm. Context, in terms of gathering direction and gathering frequency. It is shown that while the proposed algorithm and Context have the same gathering frequency, they have opposite directions of context gathering. Practical variations are also considered. By combining the proposed algorithm with Welch's device, two practical data compression methods are obtained. They, as well as Welch's LZW method, start with a small table of symbol strings and build the table during compression and decompression. In practical methods, higher compression efficiency can be gained by accelerating the growth of the table     

Analysis and improvement of SIP conformance test specification

Session initiation protocol (SIP) is one of the most popular protocols these days. There are lots of SIP implementations, but not all of them have good quality, so we need SIP conformance test to verify the conformance between the SIP implementations and SIP related protocols.     

Local and distributed SIP overload control solution improving sustainability of SIP networks

Carriers have adopted session initiation protocol (SIP) in their next generation networks. Providing carrier‐grade service requires high availability in times of component failures, avalanche restart, flash crowds and denial of service attacks, which cause overload on SIP servers. Throughput of SIP servers is largely degraded during overload. We propose an SIP overload control (SIP‐OC) solution for local and remote situations, working in hop‐by‐hop and end‐to‐end modes. Our local SIP‐OC method uses a cross‐layer approach with negligible performance impact, while the implicit nature of our remote SIP‐OC allows detection of sophisticated overload conditions such as those caused by non‐SIP entities. Our remote SIP‐OC uses transaction response time as the basis for implicit overload detection. Coupling our local and remote SIP‐OC schemes, we show that the range of ‘sustainable’ overload that can be imposed on the system improves significantly. Moreover, incorporating a 2‐means filtering mechanism into our SIP‐OC scheme makes it perform well under packet‐loss. We also show that our proposed solution is robust to network latency and SIP server capacity fluctuations. All of our results are obtained from experiments over SIP testbeds including an experimental IP multimedia subsystem. Copyright © 2016 John Wiley & Sons, Ltd.     

网络监测系统中SIP监测模块的研究与实现

为了对实现对NGN网络的建设和优化,需要一种对网络中传输的信令消息进行分析的监测系统。本文以方案思想—设计实现—结果分析为线索,首先对监测系统设计思想进行研究,然后对信令测试仪中SIP监测模块进行了详细分析。在分析SIP协议消息结构的基础上,提出了SIP协议监测的方案,并给出了SIP类的定义体和SIP协议消息解码模块流程图。在SIP解码的基础上对监测模块中最重要的CDR合成模块进行了讨论,通过实际工程测试给出合成CDR结果,从而验证了监测系统方案的可行性与可靠性。