VoIP认证与计费的设计与实现

基于RADIUS的VoIP认证系统，采用分散受理、集中管理的接入认证管理体系，数据集中存放在认证中心(RADIUS服务器)，用户身份认证由PC向网守发起，网守通过RADIUS协议向认证中心的认证服务器发起认证请求。这样，可以保证用户安全地使用网络资源，以确保用户身份的合法性。同时其落地话单经过处理，可进行计费及其它帐务处理。文中论述了RADIUS对VoIP的支持，提出了一个Gatekeeper与RADIUS结合的整体解决方案。     

高校VoIP平台搭建案例研究

本文介绍了语音在校园网上传输VoIP的技术特点、国际标准以及VoIP在校园网上的应用和发展状况,并对VoIP的技术体系结构进行了详细阐述,重点以某大学VoIP系统与传统网络的融合为实例进行研究。     

Randomized trial of a gatekeeper program for suicide prevention: 1-year impact on secondary school staff.

Gatekeeper-training programs, designed to increase identification and referral of suicidal individuals, are widespread but largely untested. A group-based randomized trial with 32 schools examined impact of Question, Persuade, Refer (QPR) training on a stratified random sample of 249 staff with 1-year average follow-up. To test QPR impact, the authors introduced and contrasted 2 models of gatekeeper-training effects in a population: gatekeeper surveillance and gatekeeper communication. Intent-to-treat analyses showed that training increased self-reported knowledge (effect size [ES] = 0.41), appraisals of efficacy (ES = 1.22), and service access (ES = 1.07). Training effects varied dramatically. Appraisals increased most for staff with lowest baseline appraisals, and suicide identification behaviors increased most for staff already communicating with students about suicide and distress. Consistent with the communication model, increased knowledge and appraisals were not sufficient to increase suicide identification behaviors. Also consistent with the communication model were results from 2,059 8th and 10th graders surveyed showing that fewer students with prior suicide attempts endorsed talking to adults about distress. Skill training for staff serving as "natural gatekeepers" plus interventions that modify students' help-seeking behaviors are recommended to supplement universal gatekeeper training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

H.323网守在呼叫路由中的应用研究

以H．323网守在VoIP体系结构中的作用和地位为基础,重点阐述了H．323网守在呼叫路由中的应用;通过实际的项目开发经验和理论研究成果,提出了一种分布式网守拓扑结构中域内和域间呼叫路由的解决方案,使用这种网守拓扑结构作为对分级网守结构中网络拓展的一种补充,从而加速了H．323网守在VoIP体系中进行注册节点地址解析和呼叫路由的进程。目前,这种方法在VANLINK公司H．323网守中已经得到证实。     

Implementation of a prototype VoIP system

VoIP(Voice over IP) is a rapidly growing area with great market potential.To promote it for both commerical and research purposes,a prototype VoIP system based on state-of -the -art otorola communication techniques has been developed.It is a gateway system integrating a PBX and a VoIP module.All components that H.323 defines to supprot VoIP are implemented in the VoIP module,though in a simplified manner,As an embedded system,the system features realtimeness and task distributiveness.A number of addiitonal techniques are used to improve the performance,including noise suppression,zero copy,and buffer structure optimization.When refined in interoperability,the system will also readily serve as a product.     

一种基于H.235协议的关守消息认证机制

首先对基于用户秘密散列签名的关守消息认证机制做了简单介绍,然后针对该机制的不足之处提出了一种基于H.235协议的改进方法,具有安全性高,速度快,管理方便等优点.     

SIP与H.323的比较与互通

文中从实际出发,参考了RFC3261和H.323文献,详细阐述了SIP和H.323的区别,提出了两者在网络中互通的基本概念。在此基础上,通过网际协作功能(IWF)提出了SIP和H.323的互通模型。最后,在软交换网络体系中,提出了SIP和H.323互通的网络构架,以满足未来网络和业务发展的需要。     

IP电话常见问题及解决方法

本主要介绍了IP电话一期网络在运行中所出现的问题和原因，并提供了解决方法，为二期网络建设和运行维护提供指导性建议。     

一种基于VRRP的网闸高可用性协议模型

当前的高可用性标准协议无法满足网闸等多机网络设备的高可用性需求。为解决该问题,提出一种基于虚拟路由器冗余协议(VRRP)的网闸高可用性协议模型。在VRRP协议基础上添加一个本地测试模块,在向其他设备发送宣告报文的同时,向本地另一端发送测试报文,对协议的功能、报文格式、状态转换图进行文字和形式化描述,根据协议完成模块和流程设计,从而实现原型。实验结果表明,当正常工作的主用机发生状况时,备用机可自动接替主用机工作,在优先级高的主用机故障解除并恢复正常后会重新接管工作,达到了预期效果。     

Single-step electrochemical functionalization of double-walled carbon nanotube (DWCNT) membranes and the demonstration of ionic rectification

Carbon nanotube (CNT) membranes allow the mimicking of natural ion channels for applications in drug delivery and chemical separation. Double-walled carbon nanotube membranes were simply functionalized with dye in a single step instead of the previous two-step functionalization. Non-faradic electrochemical impedance spectra indicated that the functionalized gatekeeper by single-step modification can be actuated to mimic the protein channel under bias. This functional chemistry was proven by a highly efficient ion rectification, wherein the highest experimental rectification factor of ferricyanide was up to 14.4. One-step functionalization by electrooxidation of amine provides a simple and promising functionalization chemistry for the application of CNT membranes.