基于SIP的宽带实时多媒体通信研究与实现

介绍了会晤创建协议(SIP)，提出了基于SIP的应用系统——SRMCS，针对该实时多媒体通信系统，分析了其音频模块的实现和背景噪音的处理、视频模块的实现和视频的流畅播放，并就实时多媒体通信系统的关键问题——视、音频同步给出了可行的解决方案，最后还探讨了本系统中信令流和媒体流的传输方式。     

Evaluation of performance enhancing proxies in internet over satellite

Performance enhancing proxies (PEPs) are widely used to improve the performance of TCP over high delay‐bandwidth product links and links with high error probability. In this paper we analyse the performance of using TCP connection splitting in combination with web caching via traces obtained from a commercial satellite system. We examine the resulting performance gain under different scenarios, including the effect of caching, congestion, random loss and file sizes. We show, via analysing our measurements, that the performance gain from using splitting is highly sensitive to random losses and the number of simultaneous connections, and that such sensitivity is alleviated by caching. On the other hand, the use of a splitting proxy enhances the value of web caching in that cache hits result in much more significant performance improvement over cache misses when TCP splitting is used. We also compare the performance of using different versions of HTTP in such a system. Copyright © 2003 John Wiley & Sons, Ltd.     

基于椭圆曲线的限制代理签名方案

基于椭圆曲线提出了一个限制代谢签名者的代理签名次数和代理签名期限的代理签名方案。原始签名者在代理签名有效期内，能限制代理签名者的代理签名次数，当代理签名有效期过后，能收回代理签名权。该方案克服了通常的代理签名方案中一旦原始签名者将答名权委托给代理签名者，就无法控制代理签名者的代理签名次数，无法收回代理签名权的缺点，该方案是基于椭圆曲线，采用一次一密签名构造的，具有安全性高，速度快，密钥量小，便于实现等优点。     

Estimating and eliminating redundant data transfers over the web: a fragment based approach

Redundant data transfers over the Web, can be mainly attributed to the repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken down to fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process, we propose solutions for dealing with redundant data transfers. This paper has been based on our previous work on ‘Web Components’ but also on related work by other researchers. It utilises a proxy based, client/server architecture, and imposes changes to the algorithms executed on the Proxy server and on clients. We show that our proposed solution can considerably reduce the amount of redundant data transferred on the Web. Copyright © 2004 John Wiley & Sons, Ltd.     

Modbus在电除尘器系统中的应用

介绍了通过应用Modbus协议实现主PLC和3台EPIC进行通讯的通讯服务器的软硬件实现方法。     

The Content Driven Mobile Internet

The development of future mobile networks will be driven, in large part, by content and web based services. In this paper, we examine several performance, scalability and architectural challenges faced by future mobile web applications and how advanced mobile content delivery techniques can address these challenges. We review existing content delivery using a taxonomy that consists of three categories: network scaling, end system acceleration, and content and protocol optimization. While wireline content delivery focuses on network and server scalability, mobile content delivery will likely benefit most from optimizing radio link usage. We also present our ongoing work in this area, which extends the functionality of edge caching to the terminal, uses user interest correlation information to maintain low terminal power consumption and adds a new dimension to radio resource management. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stateful session handoff for mobile WWW

This paper proposes a web session handoff system that can hand over not only stateless but also stateful sessions between homogenous and heterogeneous user devices to enable uninterrupted and seamless web access. The proposed system adopts a proxy-based approach and an optional client-assisted scheme in order to track and hand over session information. In the proposed system, a session is registered at a User Agent Proxy (UAP) and then tracked by the UAP so that the session can be handed over from one device via the UAP to another device. In addition to session information tracked by a UAP, the UAP can hand over more comprehensive session information by using the client-assisted scheme. Compared with client-based approaches, our design has several advantages, such as less modification to user devices, practicability, and fault tolerance. We have implemented a UAP on a PC and client programs for both PC and PDA. The implementation can successfully hand over between PC and PDA a stateful session for online shopping applications.     

一个通用代理计费系统开发框架的设计与实现

用户在不同的网络环境中选择不同的代理软件实现上网和用户管理，这些代理软件既有共性又各具特色，为减少开发不同代理计费软件的工作量，提高开发效率，加快开发周期，提出利用软件重用的思想，将代理软件的差异集中到少数几个类的实现上，设计并实现一个通用代理计费系统开发框架，基于此框架利用相对简单的步骤开发了基于SQUID的代理计费系统，验证了框架的实用性和可行性，达到了设计目标。     

Improvement on threshold proxy signcryption scheme

Signcryption is a public key or asymmetric cryptographic method that provides simultaneously both message confidentiality and integrity at a lower computational and communication cost. This paper presents a （t, n） threshold proxy signcryption scheme in which no less than t proxy agents in the proxy group can produce the signcryption cryptogram. combines the functionality of threshold proxy signing and encryption. The proposed scheme combines the functionality of both threshold proxy signing and encryption, and provides fair protection for the sender and the proxy agents. This scheme is secure against attack of public key substitution. It also satisfies security properties such as confidentiality and authenticity.     

基于Modbus协议的外输计量监控系统的设计与实现

原油的外输计量系统没有配套的上位机系统,其操作存在一定的缺陷。针对这种情况,在详细介绍了Modbus协议和CRC校验的基础上,提出了基于Visual Basic环境下与流量计算机通信的系统设计方案,在该设计中实现了基于Modbus协议的串口通信以及CRC校验。实际验证,该系统能够有效地解决原有问题。