P2P网络应用中对等通讯技术的研究

本文分析了NAT的基本原理以及其对P2P网络应用的影响,提出通过在Internet上部署一台注册服务器,利用UDP穿越NAT实现P2P网络中双向对等通讯的解决方案;同时,提出通过NAT之后的主机定时向服务器发送保持映射的UDP消息,解决了NAT中动态地址映射保持问题。     

P2P网络穿越中NAT类型检测的原理与实现

随着P2P网络技术的应用普及,更多的局域网主机需要连接到P2P的网络,但P2P对等网络要求网络中所有节点都能直接对等交换信息,这就使得P2P网络应用必须解决NAT穿透,实现双向对等通讯。文章通过对NAT穿透技术的原理分析,设计了一种NAT类型检测的算法,从而提高实际NAT穿透过程中的效能。     

P2P网络中基于UDP穿透NAT技术的研究

当前IPv6尚末全面实施,Internet依然采用32位的IPv4地址。由于IPv4提供的公网IP地址已接近枯竭,导致NAT技术在Internet上广泛应用,而NAT技术的应用给P2P通信带来了障碍。本文试图理清这些问题,并且着重讨论P2P网络中基于UDP穿透NAT的技术。     

P2P网络模型及其应用研究

对等网络(Peer-to-Peer,简称P2P)是基于P2P拓扑发展起来的,在Internet上实施网络计算的新模式。在这种模式下,服务器与客户端的界限消失了,网络上的所有节点都可以"平等"共享其他节点的计算资源。在一个P2P系统里,计算机能够同时扮演客户机和服务器的角色,他的作用在任何任务里都取决于当时系统适合于工作的对象。     

P2P网络模型及其应用研究

对等网络(Peer-to-Peer,简称P2P)是基于P2P拓扑发展起来的,在Internet上实施网络计算的新模式.在这种模式下,服务器与客户端的界限消失了.网络上的所有节点都可以"平等"共享其他节点的计算资源.在一个P2P系统里.计算机能够同时扮演客户机和服务器的角色,他的作用在任何任务里都取决于当时系统适合于工作...     

P2P网络中利用JXTA穿越NAT的方法研究

P2P是当今网络技术的研究热点,如何在对等节点之间建立有效的连接也成为影响P2P应用的一个关键问题,但由于NAT设备的大量存在,使得因特网中的对等节点很难与NAT后的对等节点建立有效的连接.在分析了NAT的基本原理、阻碍对等节点之间通信的原因以及已有的解决方法的基础上,提出了一个基于JXTA的端点和管道技术的解决方案并给出一个开发实例.     

P2P网络体系及检测技术研究

P2P网络是一个分布式网络模型,也叫对等网络,网络中的节点都有相同或相近的责任,其特点就是降低以服务器为核心的地位,充分整合分布在终端主机上的资源,如CPU资源、网络资源和存储资源等。跟传统的C/S模式有着巨大的区别,也就是说,在对等网络中,各个节点的地位是平等的,可以同时作为服务端又可以作为客户端。     

P2P网络模型的研究与分析

对等网络P2P(Peer to peer)是Internet网实现下一次飞跃的关键,本文首先分析了P2P网络以及它和其它传统网络模式的差别,P2P现有的各种应用模型的优势与不足之处。在已有的对等点发现方法的基础上提出了主动搜索模型。     

点对点通信软件设计

点对点通信技术(Peer to Peer,P2P)的核心,就是研究如何使Internet上任意两台电脑之间直接通信.根据网络结构的不同,将点对点通信分成以下四种情形:两个客户端都在公共网络中;两个客户端同时在同一个私有网络中;一个客户端在公共网络中,一个客户端在私有网络中:两个客户端位于不同的私有网络中.其中后面两种情形,需要在服务器的协调下,通过打洞(穿越NAT)才能实现点对点通信,这正是P2P技术的难点.在深入研究P2P的基础上,基于UDP实现了一个P2P软件,该软件具有网络聊天和网络文件传输的功能.     

P2P网络中主流DHT搜索算法的分析比较

对等（P2P）网络是实现下一代互联网的重要组成部分。对等网络的可用性依赖于时网络上数据的高效的查找和提取方法．如何高效的定位和搜索P2P网络上的资源是P2P网络实现的最为关键的问题。本文首先从P2P的定义出发，深入介绍了几种主流的DHT算法与协议并时每种协议进行了讨论。文章的最后展望了DHT在未来的发展趋势。     

Secure seamless peer-to-peer (P2P) UDP communication using IPv4 LSRR option and IPv4+4 addresses

The current structure of the Internet, with hosts behind network address translation (NAT) boxes, causes well-known problems for P2P applications. There are several proposals, e.g., STUN, UPnP, MIDCOM, TURN among others, to enable P2P UDP communication for nodes behind NAT boxes, but each technique offers a partial solution that works in special limited cases and fails in others. In this paper, we present a framework based on the use of IPv4+4 addresses and the standard IPv4 Loose Source Record Route (LSRR) option that offers a complete solution to the secure seamless P2P UDP communication problem. Our proposal requires no changes whatsoever to end-host protocol stacks and Internet routers. The only requirement is a simple upgrade of border routers with a new LSRR-based packet forwarding algorithm for the P2P UDP traffic. We detail our implementation of a Linux-based border router that runs the proposed forwarding algorithm, and describe how applications requiring P2P UDP communication such as Voice over IP (VoIP) using SIP can benefit from our framework.     

Optimizing BitTorrent-like peer-to-peer systems in the presence of network address translation devices

BitTorrent nowadays is one of the most important peer-to-peer (P2P) file-sharing applications on the Internet, and it has also inspired many other P2P applications such as live or on-demand video streaming services. On the other hand, Network Address Translation (NAT) has become pervasive in almost all networking scenarios, from residential Internet access to enterprise networks. Despite the effort of NAT traversal, it is still very likely that P2P applications cannot receive incoming connection requests properly if they are behind NAT. To quantify the performance impact of NAT on BitTorrent-like P2P systems, we have created and validated a detailed but tractable mathematical model. We have also proposed and briefly examined a simple but effective strategy to mitigate the negative impact on NAT peers. In this paper, we further extend our model to cover the proposed biased optimistic unchoke strategy, and optimize the system performance in terms of both average peer download time and system finish time. We also create a new, faster Java-based BitTorrent simulator, which is used to validate the extended model and show the optimality of the proposed strategy and its boundary conditions.     

混合型网络中DDoS攻击的入侵扫描研究

现有网络中网络地址转换（NAT）的存在使得其后网络中的主机对外部网络变得不可见,IPv6庞大的地址空间也使得攻击者利用传统的随机地址扫描策略很难找到有漏洞主机。概述当前DDoS攻击的基本原理,具体分析了随着因特网体系结构的变化,网络NAT等设施的出现对DDoS攻击所带来的影响。针对传统理论在研究DDoS攻击过程中的一些不足,提出了一种基于搜索引擎技术和Teredo服务的新型扫描策略,以及对NAT后主机实施DDoS攻击的具体方法。仿真实验证明这种新型DDoS入侵攻击更加有效,对复杂网络环境的适应性也更强。     

使用UDP穿越P2P网络中NAT的方法

介绍了基于Internet的P2P技术和NAT的基本原理，分析了NAT对P2P的影响。讨论了在现有通信协议上实现点对点应用传输所必须解决的，端到端定位，局域网IP地址解析等技术。最后给出了一个利用UDP Sockets技术实现P2P网络应用的实例。     

基于NAT穿越技术的P2P通信方案的研究与实现

分析了广泛存在的NAT(network address translator)设备对P2P(peer-to-peer)通信的影响,阐述了反向连接技术和UDP(user datagram protocol)打洞技术等NAT穿越技术,基于这些技术提出了一套P2P通信方案并予以实现,使得位于NAT之后的主机可以在中间服务器的协助下穿越NAT建立起P2P通信会话并在此后直接进行P2P通信.最后,对NAT穿越技术涉及的一些关键问题进行了分析和说明.     

一种UDP穿越NAT的新方案

网络地址转换是解决IPV4地址紧缺的有效方法,但对P2P技术的应用产生了负面影响。该文分析网络地址转换对P2P网络产生的负面影响,研究NAT端口映射类型及其检测方法,给出了一种用于P2P网络的穿越NAT协议。该协议可以解决P2P网内私网计算机之间建立直接UDP通信的问题,从而改善了P2P网络连通性。     

Can: A context-aware NAT traversal scheme

Network Address Translation (NAT) is a technique commonly used to share one public IPv4 address among several hosts located behind a NAT device. NAT devices typically block session requests originating from outside, causing NAT traversal problem that prevents the establishment of peer-to-peer (P2P) sessions. There have been many proposals for the NAT traversal problem. However, existing methods induce high connectivity check delay and resource demand when finding a communicating path, calling for a routine that determines the path best suited for a given pair of communicating peers. This study proposes CAN, a Context-Aware NAT traversal scheme which gathers and exchanges network-context information to find the most appropriate path for two communicating peers behind NAT devices. We have implemented CAN and conducted extensive experiments with off-the-shelf NAT devices to compare the performance of CAN with Interactivity Connectivity Establishment (ICE), the most acknowledged approach to creating a session across NATs. Experimental results show that CAN outperforms ICE in terms of direct communication ratio, connectivity check delay and message overload when checking connectivity.     

Performance evaluation of Recursive Distributed Rendezvous based service discovery for Peer-to-Peer Session Initiation Protocol

Recursive Distributed Rendezvous (ReDiR) is a service discovery mechanism for Distributed Hash Table (DHT) based Peer-to-Peer (P2P) overlay networks. One of the major P2P systems that has adopted ReDiR is Peer-to-Peer Session Initiation Protocol (P2PSIP), which is a distributed communication system being standardized in the P2PSIP working group of the Internet Engineering Task Force (IETF). In a P2PSIP overlay, ReDiR can be used for instance to discover Traversal Using Relays around NAT (TURN) relay servers needed by P2PSIP nodes located behind a Network Address Translator (NAT). In this paper, we study the performance of ReDiR in a P2PSIP overlay network. We focus on metrics such as service lookup and registration delays, failure rate, traffic load, and ReDiR’s ability to balance load between service providers and between nodes storing information about service providers.     

P2P网络中TCP穿透NAT的解决方案

随着Internet网络用户的迅速增加,IPv4地址出现了严重的短缺.网络地址转换(NAT)设备的出现解决了这个问题,但也给P2P通信带来了困难.目前,UDP穿透已经得到较好地解决,TCP穿透NAT虽然有一些解决方案,但都不完善.文章提出一种由应用程序来协助完成TCP穿透NAT的方案,减轻了对第三方服务器的依赖,提高了建立连接的安全性和效率.