基于协议分析的IM阻断策略及算法分析

本文根据即时通讯(IM)的协议模型,在TCP层和即时通讯协议层分析了阻断即时通讯的可能性,分别提出了基于TCP层和即时通讯协议层的协议分析的阻断策略.在TCP层,通过插入FIN报文或RST报文,以关闭TCP连接(特别是与登录服务器的连接);在即时通讯协议层,通过对相应字段的值进行设置,使客户端进入不活动状态.为使阻断策略能够有效地实施,本文也提出了一个消息驱动的实现算法.通过对Yahoo! Messenger的阻断实验,证明了本文提出的方法能够高效地完成阻断任务(平均数据包量不超过2.5个).用统计分析的方法对它们的性能进行比较,结果表明各种方法的效率在不同的背景流量下没有显著的差异,通过消息驱动算法实现的基于协议分析的阻断策略,其工作效率不受背景流量的影响.另外,即时通讯数据的触发方式,使得发送的阻断包的数量与背景流量无关,也不对网络负载造成明显的影响.本文的工作为实施即时通讯的阻断提供了有效的解决方案.     

基于社会计算的IM恶意代码防御机制

即时通信(IM,Instant Messaging)网络已成为恶意代码传播的主要途径之一,本文提出了一种基于社会计算的IM恶意代码防御机制:利用用户与好友之间的社会信任关系,通过社会计算集成网络中多种反病毒软件的检测结果及用户的安全经验形成群体智慧,从而构成一个分布式协作防御机制.该机制利用即时通信网络平台,并依据好友间的交互行为计算动态信任,在IM客户端部署方案,用户之间实时相互协作抵御通过IM传播的恶意代码.实验结果表明,在大多数用户接受好友警告的情况下,即时通信网络中所有节点最终都被免疫,提高了整个社会网络防御IM恶意代码的能力.     

Quality-based evaluation of multimedia synchronization protocolsfor distributed multimedia information systems

Distributed, networked multimedia information systems will be a critical component of technology-based information infrastructures in the future. We present an infrastructure for supporting multimedia applications. We discuss various characteristics of multimedia data and the effect of the network on the required quality of presentation for multimedia data. We present a suite of synchronization protocols to support the quality of presentation. The crux of these protocols is the scheduling of multimedia information for synchronized delivery, over broadband networks with limited resources, and is identified as an NP-hard problem. We introduce two parameters which can be used to measure the performance of end-to-end synchronization protocols in a network supporting distributed multimedia applications. We propose and implement several heuristic scheduling algorithms, and compare their performance. We deduce the appropriateness of these algorithms in different types of distributed multimedia environments     

基于VB和ADO的机考批改系统

即时通信目前有4种主要协议:即时信息和空间协议(IMPP)、空间和即时信息协议(PRIM)、针对即时通信和空间平衡扩充的进程协议SIP(SIMPLE)以及XMPP。XMPP是其中最重要的协议之一,是基于XML流的即时通信协议。首先简单介绍XMPP出现的背景,然后详细解析XMPP中的XML流、XML节和JID等基本概念,采用一些实例说明这些基本概念在即时通信中的应用,最后还对XMPP的互通性、安全性及加密特征进行了讨论。     

Exploring the routing strategies in next-generation satellite networks

Employing an efficient routing algorithm in satellite networks is a critical issue, because satellite network resources are costly and must be managed in an optimal and effective manner. Because of the particular features of satellite networks, such as dynamic topology, non-homogeneous traffic distribution, limited power and processing capabilities, and high propagation delays, new routing approaches should be developed. In this article, we first examine these properties with particular emphasis on their effect on the routing objectives. Subsequently, we provide a survey of various routing protocols that aims to address the crucial issues stemming from these properties of satellite systems. We classify these protocols according to their objectives, and discuss their advantages and disadvantages. We also elaborate on relevant technical aspects.     

Introduction to the Special Issue on Instant Messaging in the Workplace

Instant messaging (IM) in the workplace has become an important topic for research as IM applications have proliferated in the corporate context. However, much of the work done to date has examined IM use from the consumer perspective, leaving us with little guidance as to its use in the office. This special issue addresses this shortcoming in the literature, providing several important studies on workplace IM use. One paper examines the use of IM in resolving differing points of view among coworkers. Another paper studies workplace communications costs and the role IM has in contributing to them by increasing communication volume. Two papers in the issue examine workplace IM in an international context, considering both cross-cultural and demographic issues that impact IM use.      

电信运营商在即时通信领域的竞争策略

即时通信已经变成了一个能量十足的互联网利器,正逐渐深入人们的生活及相关领域,正在给人们的沟通方式注入新的活力,同时也给电信行业带来了挑战和机会。目前该行业的现状是竞争激烈、差异化小,进入门槛低,使后进入者面临一定的困难和挑战。电信运营商要进入该市场,应发挥自己的资源优势,实施差异化战略,着力打造特色服务,将重点放在音视频质量上,为将来与固网及移动网的互联互通做准备等方面。     

Analyse des fonctions des protocoles ipsec et leur intégration dans un réseau privé virtuel

Many approaches may lead to integrate security functions in the intranet/internet services. These functions may be placed at the application layer or at lower OSI layers. IPsec suite protocols were specified by IETF in order to integrate security functionality at network layer. This paper describes the features of IPESC protocols and identifies the aspects which are not standardized. The network translation address (nat) functionality used by routers and firewalls is not always compatible with IPESC. We describe and discuss some solutions for the compatibility of ipsec and nat. The last part of this paper describes a typical architecture for ip vpn based on IPSec technology.     

Self-organization in spontaneous networks: the approach of DHT-based routing protocols

The increase demand for flexibility, spontaneity, adaptability, independence of a wire infrastructure, and easy-managed architectures are driving a revolutionary change in the network community research. The number of proposals in the literature related to technologies like ad hoc, and more recently, sensor networks witnesses for the interest on the deployment of distributed, autonomous, spontaneous, and self-organizing systems. Distributed hash tables (DHTs) have been largely adopted as a useful substrate to the design and specification of self-organizing systems. The functionality of decoupling identification from location, and of providing a general mapping between them, have made the DHT abstraction an interesting principle to be integrated in network-level routing protocols. Although improving scalability, this integration also introduces new challenges for the network architecture specification. In this paper, we examine the main components related to the design of network architectures having DHT interactions in mind. We survey the recent proposals that attempt to deal with DHT-based self-organizing systems, and discuss their differences according the way in which the DHT functionalities are applied. It is verified that initial decisions of the designers about priorities of different issues and requirements are reflected on proposals’ strengths and weakness. We conclude our investigations by presenting a discussion about the proposals’ more significant features. Finally, based on our concluding observations, we also discuss a new and promising approach for the deployment of a distributed and self-organizing system.     

A heuristic approach to establishing punctuation convention in instant messaging

Instant Messaging (IM) features informal writing styles such as the omission of punctuation. Punctuation plays an important role in representing prosody and facilitating syntactic processing during communication. The discrepancy between the recognized importance and actual inadequate usage of punctuation in IM calls for establishing punctuation convention for more effective online communication. The research uniquely reported here addressed two research questions. The first was whether punctuation had an impact on the effectiveness of IM. The results of an empirical study showed that the majority of surveyed participants perceived punctuation to be somewhat important. This led to the investigation of the second research question: how to restore omitted punctuation in instant messaging to help develop punctuation convention effectively? We designed and implemented a technical solution for recovering punctuation based on heuristics rules and an evaluation of this approach showed satisfactory performance. A detailed analysis of punctuation in archived instant messages revealed several patterns of omitted punctuation. The findings of this research not only advance our understanding of the stylistic convention, but also provide positive evidence for establishing punctuation convention in IM. As IM continues to pervade daily communication, punctuation convention in IM deserves closer attention.     

Wormhole attacks in wireless networks

As mobile ad hoc network applications are deployed, security emerges as a central requirement. In this paper, we introduce the wormhole attack, a severe attack in ad hoc networks that is particularly challenging to defend against. The wormhole attack is possible even if the attacker has not compromised any hosts, and even if all communication provides authenticity and confidentiality. In the wormhole attack, an attacker records packets (or bits) at one location in the network, tunnels them (possibly selectively) to another location, and retransmits them there into the network. The wormhole attack can form a serious threat in wireless networks, especially against many ad hoc network routing protocols and location-based wireless security systems. For example, most existing ad hoc network routing protocols, without some mechanism to defend against the wormhole attack, would be unable to find routes longer than one or two hops, severely disrupting communication. We present a general mechanism, called packet leashes, for detecting and, thus defending against wormhole attacks, and we present a specific protocol, called TIK, that implements leashes. We also discuss topology-based wormhole detection, and show that it is impossible for these approaches to detect some wormhole topologies.     

Involuntary migration in cyberspaces: The case of MSN messenger discontinuation

Instant messaging (IM) is one of the most popular Web 2.0 tools for the facilitation of synchronous communication, collaboration, and social interaction among users. The chances that incumbent instant messaging (IM) users will suffer from involuntary switching have increased because competition can eliminate their service/technology providers. This concern leads to our research question: what factors influence IM users’ decision-making in involuntary switching? In light of the above concerns, this study aims to extend the push–pull–mooring (PPM) framework and the migration theory to the context of service involuntary switching by incorporating the notions of network effects and regret. Our model theorizes that four constructs of network effects (referent network size, future expectation, perceived complementary, and perceived compatibility), similarity and innovativeness (pull factors), switching cost (mooring factors), and three push factors regarding migration plan and outcome (dissatisfaction with technical quality and information quality of the migration plan and regret) can affect users’ intention to migrate to other IM services and subsequently alter their migration behaviors. This hypothetical model used in this study has been empirically validated using data collected from 381 IM users. Implications for theory and practice are also discussed.     

不同网络制式下QQ业务性能分析及优化方案

本文对不同网络制式下QQ业务的性能进行分析并提出相应优化方案.QQ类业务具有小数据分组、不连续传输等特征,对移动通信网络的信令面与业务面资源产生了较大的占用与浪费.不同网络制式下,由于资源分配机制不同,QQ业务对网络的影响不同,针对其的优化机制也有所不同,本文分析了2G (GSM)、3G(TD-SCDMA)及B3G (...     

Instant messaging and presence technologies for college campuses

Instant messaging is an application that enables networked users to send and receive short messages. Presence provides information about users' reachability and willingness to accept/reject a brief chat session. Various proprietary IM and presence (IM&P) solutions are currently on the market, and standards are emerging. There are interoperability problems between the two dominant standards (SIMPLE and XMPP); as a result, this important application is finding difficulty in widespread deployment within college campuses and businesses. We describe a brief history of the development of IM&P technology discuss the current standardization work being done within IETF, and present an overall architecture of emerging standards. We provide a comparison between the SIP/SIMPLE and Jabber/XMPP standards. We also present data and its analysis from a survey of campus organizations that sheds light into the main issues of deploying, managing and provisioning of IM&P services on college campus.     

P2PSIP原理和应用

SIP协议是当前VoIP和IM等多媒体协议的呼叫建立协议。P2P技术提供了分布式的网络架构中通信节点之间得对等通信能力,P2P网络架构经历了集中目录式网络架构、纯P2P网络架构、混合式P2P网络架构和结构化P2P网络架构。通过引入P2P技术,SIP网络的能力可以得到增强。P2PSIP网络主要有两个重要的操作:对P2P节点的操作和用户层面的操作。     

Analysis and Design of Instant Message System Based on P2P

By analyzing current development conditions of mainstream Instant Message technologies and services,some detailed discussion about technical solution and formal operation deployment strategies of P2P Instant Message Services based on Internet is made.Several crucial problems of P2P Instant Message System about services management,interconnection with other instant message,security and profit-making mode are analyzed,,and how to develop P2P IM Services is proposed.     

个人通信系统中的一种移动用户登记认证协议

假冒和窃听攻击是无线通信面临的主要威胁。在个人通信系统中,为了对无线链路提供安全保护,必须对链路上所传送的数据/话音进行加密,而且在用户与服务网络之间必须进行相互认证。近年来,人们在不同的移动通信网络(如GSM,IS-41,CDPD,Wireless LAN等)中提出了许多安全协议。然而,这些协议在个人通信环境中应用时存在不同的弱点。本文基于个人通信系统的双钥保密与认证模型,设计了用户位置登记认证协议;并采用BAN认证逻辑对协议的安全性进行了形式化证明,也对协议的计算复杂性进行了定性分析。分析表明,所提出的协议与现有的协议相比具有许多新的安全特性。     

Jingle: Jabber Does Multimedia

Instant messaging is a powerful tool for real-time communication and online collaboration. IM's early focus was text communication, but with the ubiquity of multimedia-enabled devices, there has been great interest in extending IM to support multimedia interactions. Jabber is an open-standards-based approach for IM. The article describes the development of new enhancements to Jabber that provide a set of multimedia extensions called Jingle     

Performance of Unidirectional Broadcast Local Area Networks: Expressnet and Fasnet

Local area communication networks based on packet broadcasting techniques provide simple architectures and flexible and efficient operation. Unidirectional broadcast systems use a unidirectional transmission medium which, due to their physical ordering on the medium, users can access according to some efficient distributed conflict-free round-robin algorithm. Two systems of this type have been presented in the literature: Expressnet and Fasnet. In this paper we briefly describe these two. We identify three different service disciplines achievable by these systems and discuss and compare the performance of each. These systems overcome some of the performance limitations of existing random-access schemes, making them particularly well suited to the high bandwidth requirements Of an integrated services digital local network.     

ID/Locator Split-Based Mobility Scheme for Heterogeneous New Generation Network

The new generation network or the future Internet should treat mobile hosts as first-class objects and allow them to move freely across different networks that use heterogeneous protocols. For this purpose, this paper presents a mobility scheme, designed on the basis of the ID/locator split concept. The scheme provides mobility support from the identity layer, a shim layer inserted between the transport and network layers in the new generation network architecture. Mobility functions are independent of network layer protocols, thus they support mobility across heterogeneous network protocols. These functions are distributed in both end hosts and edge routers so that the scheme provides seamless mobility by reducing handover delay and consequent interruption in communication sessions.