Validation of H-P2PSIP, a scalable solution for interoperability among different overlay networks

This paper reports the results of experiments from an implementation of H-P2PSIP, a hierarchical overlay architecture based on the ongoing work in the IETF P2PSIP Working Group. This architecture allows the exchange of information among different independent overlay networks through the use of a two-layer architecture based on super-peers and hierarchical identifiers. The validation of this proposal is based on a Linux based real implementation where we have used four different scenarios with 1,000 peers in order to perform different experiments. We have obtained results for different parameters such as routing performance (number of hops), delay, routing state (number of overlay routing entries) and bandwidth consumption.     

基于分层P2PSIP的移动终端跨域切换方案

提出了一种基于分层P2PSIP的移动终端跨域切换方案.通过结合P2P定位方式和SIP(Session InitiationProtocol)应用层对移动切换的支持,解决了终端在不同P2P覆盖网间移动后定位的问题.基于SIP)的终端在不同IP子网间移动后,为了正常定位和维持当前会话,必须采取某种移动切换机制.常用的切换机制包括Mobile IP方式和SIP应用层的移动切换支持.在分布式P2PSIP环境中,移动切换问题仍然存在.实际环境中,一定范围内往往有多个相邻的P2P覆盖网,为了使处于不同P2P覆盖网的终端之间可以互相定位和发起会话,可以将独立的P2PSIP网络划分为两个层次,分别用于内部SIP会话和不同P2P网络间的交互.分析并扩展了分层P2PSIP的网络架构,设计了一套对应的切换方案,使得处于分层P2PSlP中的任意两个终端之间可以被定位和发起跨域会话.     

P2PSIP网络与PSTN的一种互通机制

P2PSIP用P2P算法实现SIP的位置管理功能,解决了单点失效问题,有良好的可扩展性,将成为VoIP的关键技术。现有相关研究缺乏对不同网络互通的深入探讨。提出P2PSIP网络与PSTN的一种新颖的互通机制,并且基于该机制设计了一个易于实现的P2PSIP终端与PSTN电话互通的原型系统。互通的关键设计是一个具有双重身份的网关,在P2PSIP网络中作为对等端,在PSTN中负责连接电话机。经测试分析,该互通机制可以应用于实际网络,实现P2PSIP网络和PSTN之间的会话建立。     

基于身份的P2PSIP可认证密钥协商方案

为解决点对点会话初始协议(P2PSIP)的安全性问题,根据其分布式特点,结合身份公钥密码,提出一种可认证密钥协商方案。分析其安全性、运算效率和密钥托管等问题。该方案可以实现P2PSIP呼叫过程的双向身份认证和密钥协商,抵抗中间人攻击、重放攻击和离线密码攻击,防止消息体篡改、会话劫持和身份欺骗。     

P2PSIP系统子网间会话建立延迟的研究

为了解决由于网络节点的大量增加引起的分层P2PSIP系统中子网间用户会话建立的高延迟问题,提出了利用上层覆盖网采用单跳HDT算法的解决方案。对现有的P2PSIP网络进行了研究,把会话建立时用户定位的延迟分为在子网内部和上层覆盖网中两个部分。利用单跳DHT算法来减少子网间用户定位时消息在上层覆盖网中路由的跳数,从而可以降低平均延迟时间。通过对该方案的可行性分析和延迟的比较,表明了该方案是可行的。     

基于Kademlia算法的P2PSIP系统的研究与设计

本文首先概述了基于C/S模式的传统SIP系统的缺陷、P2PSIP系统的由来及发展现状,然后提出了一种构建于P2P层之上的SIP网络电话(P2PSIP)系统的设计方案,其中P2P层采用全分布式哈希表算法Kademlia算法实现;接着重点分析了该方案中DHT(Kad)模块的工作机制以及SIP over P2P中的交互消息;最后给出基于该方案的原型系统的测试结果。     

P2PSIP系统的路由表安全研究

针对P2PSIP系统面临的Eclipse攻击，提出一种基于双向路由表的防御机制。每个节点同时维护路由表和反向路由表，并周期性地随机审计路由表和反向路由表中的节点，以确保每个节点的入度和出度一致。仿真实验表明，该方法能将路由表污染程度从99%降低到25%左右。     

可扩展的P2PSIP会议密钥管理协议*

针对P2PSIP多媒体会议低延时、高扩展性需求,提出一种分级的会议密钥管理协议HOAKA。根据处理能力将会议节点分成两级,由少量高性能节点负责会议管理,所有成员通过单向累加器算法协商会议密钥。研究结果表明,HOAKA不仅具有较高的安全性,而且计算、存储开销低,密钥更新时延小,具有良好的可扩展性。     

一种高效的P2PSIP认证与密钥协商机制*

针对P2PSIP分布式无中心的特点,提出一种基于无证书公钥密码技术的认证与密钥协商机制,并对其正确性、安全性和性能进行了分析讨论。该方案满足普遍认可的密钥协商安全需求,而且没有使用双线性对运算,能有效降低节点的计算开销。与已有方案相比,该方案在保持较高安全性的同时具有更高的运行效率。     

Enabling adaptive live streaming in P2P multipath networks

Live Internet streaming can be regarded as a major current multimedia delivery mode. Efficient delivery under changing network conditions is a severe challenge in the design of live streaming systems. This study analyzes the key considerations and factors influencing live stream quality during system operations, and attempts to improve present P2P (peer-to-peer) live streaming systems by allowing users to enjoy high quality of service under the limitations of network resources. The proposed R-D (Rate-Distortion) optimized-dynamic-nodes-join algorithm is based on multipath streaming concept and receiver-driven approach. This distributed algorithm enables the system to evaluate the current network status in order to optimize the end-to-end distortion of P2P networks and stay in the optimal status. Experiment results of this study demonstrate the effectiveness of the proposed approach.     

Efficient, self-contained handling of identity in peer-to-peer systems

Identification is an essential building block for many services in distributed information systems. The quality and purpose of identification may differ, but the basic underlying problem is always to bind a set of attributes to an identifier in a unique and deterministic way. Name/directory services, such as DNS, X.500, or UDDI, are a well-established concept to address this problem in distributed information systems. However, none of these services addresses the specific requirements of peer-to-peer systems with respect to dynamism, decentralization, and maintenance. We propose the implementation of directories using a structured peer-to-peer overlay network and apply this approach to support self-contained maintenance of routing tables with dynamic IP addresses in structured P2P systems. Thus, we keep routing tables intact without affecting the organization of the overlay networks, making it logically independent of the underlying network infrastructure. Even though the directory is self-referential, since it uses its own service to maintain itself, we show that it is robust due to a self-healing capability. For security, we apply a combination of PGP-like public key distribution and a quorum-based query scheme. We describe the algorithm as implemented in the P-Grid P2P lookup system (http:// www.p-grid.org/) and give a detailed analysis and simulation results demonstrating the efficiency and robustness of our approach.     

Peer-to-peer service provisioning in cloud computing environments

This paper aims to advance the management and delivery of services in large, heterogeneous, uncertain, and evolving cloud computing environments. The goal is important because such systems are becoming increasingly popular, yet existing service management methods do not scale well, and nor do they perform well under highly unpredictable conditions. If these problems can be solved, then Information Technology (IT) services can be made to operate in more scalable and reliable manner. In this paper, we present a peer-to-peer approach for managing services in large scale, dynamic, and evolving cloud computing environments. The system components such as virtualized services, computing servers, storage, and databases self-organize themselves using a peer-to-peer networking overlay. Inter-networking system components through peer-to-peer routing and information dissemination structure is essential to avoid the problems of management bottleneck and single point of failure that is predominantly associated with traditional centralized and hierarchical distributed (grids/clouds) system design approaches. We have validated our approach by conducting a set of rigorous performance evaluation study using the Amazon EC2 cloud computing environment. The results prove that managing services based on peer-to-peer routing and information dissemination structure is feasible and offers significant performance benefits as regards to overall system reliability, scalability, and self-management.     

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.     

Sophia: A local trust system to secure key-based routing in non-deterministic DHTs

Today, many distributed applications are typically deployed at a large scale, including Grid, web search engines and content distribution networks, and it is expected for their scale to grow more in terms of number of machines, locations and administrative domains. This poses many scalability issues related to the scale of the environment they run in. To explicitly address these issues, many distributed systems and everyday services use peer-to-peer (P2P) overlays to allow other parts of the system to benefit from the fault-tolerance and scalability of P2P technology. In particular, Distributed Hash Tables (DHTs), which implement a simple put-and-get interface to a dictionary-like data structure, have been extensively used to overcome the current limitations associated with the centralized and hierarchical components of distributed systems, including data management, resource discovery, job scheduling etc.     

Using taxonomies for content-based routing with ants

This paper presents the SemAnt algorithm, a distributed content-based routing algorithm for peer-to-peer networks based on the Ant Colony Optimization meta-heuristic. Under the assumption that the shared content in the network is annotated according to a taxonomy, it is possible to determine the hierarchical relationships between queries, and to exploit this information to improve the routing process. The experimental results presented in this paper show that the performance of content-based peer-to-peer search is highly dependent on the content distribution in the network and on the network’s topology. It can be improved by exploiting the information provided by the underlying taxonomy. The degree of improvement is proportional to the degree of coherence in the content distribution.     

A comprehensive platform to manage peer churn and bandwidth fluctuations in real-time multimedia P2P networks

In the last few years, new service providers are growing in the Internet scenario to create new multimedia services. The most common approach to this end is based on peer-to-peer (P2P) networks. The new service providers are manifesting great interest not only for classical multimedia applications, like video streaming and video on demand, but also for multi-party games, private video-chat rooms, videoconference and real-time video teaching, usually containing a small number of high-interactive group members. The target of this paper is to define a multipoint multimedia communication platform for such kind of applications, accounting both peer set variation (peer arrivals and departures) and peer bandwidth modifications. In addition, a revenue model for providers of this kind of services is proposed to allow them to design their networks in order to maximize their revenue while satisfying user requirements in terms of both admission rejection probability and perceived quality on the received video stream.     

HD Tree: A novel data structure to support multi-dimensional range query for P2P networks

There are two basic concerns for supporting multi-dimensional range query in P2P overlay networks. The first is to preserve data locality in the process of data space partitioning, and the second is the maintenance of data locality among data ranges with an exponentially expanding and extending rate. The first problem has been well addressed by using recursive decomposition schemes, such as Quad-tree, K-d tree, Z-order, and Hilbert curve. On the other hand, the second problem has been recently identified by our novel data structure: HD Tree. In this paper, we explore how data locality can be easily maintained, and how range query can be efficiently supported in HD Tree. This is done by introducing two basic routing strategies: hierarchical routing and distributed routing. Although hierarchical routing can be applied to any two nodes in the P2P system, it generates high volume traffic toward nodes near the root, and has very limited options to cope with node failure. On the other hand, distributed routing concerns source and destination pairs only at the same depth, but traffic load is bound to some nodes at two neighboring depths, and multiple options can be found to redirect a routing request. Because HD Tree supports multiple routes between any two nodes in the P2P system, routing in HD Tree is very flexible; it can be designed for many purposes, like fault tolerance, or dynamic load balancing. Distributed routing oriented combined routing (DROCR) algorithm is one such routing strategy implemented so far. It is a hybrid algorithm combining advantages from both hierarchical routing and distributed routing. The experimental results show that DROCR algorithm achieves considerable performance gain over the equivalent tree routing at the highest depth examined. For supporting multi-dimensional range query, the experimental results indicate that the exponentially expanding and extending rate have been effectively controlled and minimized by HD Tree overlay structure and DROCR routing.     

AMRST: adaptive multicast routing protocol for satellite–terrestrial networks

Multicasting facilitates the distributing of multimedia information to an entire set of destinations simultaneously. However, the subsequent mass of Internet traffic usually increases the network congestion and degrades network utilization. The unexpected congestion together with limited network capacity might challenge the provision of multimedia services especially since multicast subscribers are widely scattered. The desired QoS of the ongoing services cannot be guaranteed. To address this challenge, in addition to installing new terrestrial broadband networks, another feasible solution would be to integrate now available broadcasting-oriented broadband satellite networks into the Internet backbone. This paper presents a novel adaptive multicast routing (AMRST) protocol to deliver reliable and adaptive multicast services to global subscribers, based on an integrated infrastructure, called a satellite–terrestrial network (ST network), which provides dynamic bandwidth allocation, flexible resource management and ubiquitous transmission. In the AMRST, a proposed virtual hierarchical routing tree was applied in constructing an efficient multicast tree. A routing decision model was proposed to determine routing path for the member requests. A “hierarchical membership maintenance” approach was designed to maintain the multicast membership. The scalability of the AMRST was further addressed. The AMRST not only kept the benefits of the traditional terrestrial multicast but also promoted the multicasting performance by employing the satellite broadcasting capability. The simulation results demonstrate that the AMRST performed excellently for the ST network.     

Chord-PKI: A distributed trust infrastructure based on P2P networks

Many P2P applications require security services such as privacy, anonymity, authentication, and non-repudiation. Such services could be provided through a hierarchical Public Key Infrastructure. However, P2P networks are usually Internet-scale distributed systems comprised of nodes with an undetermined trust level, thus making hierarchical solutions unrealistic. In this paper, we propose Chord-PKI, a distributed PKI architecture which is build upon the Chord overlay network, in order to provide security services for P2P applications. Our solution distributes the functionality of a PKI across the peers by using threshold cryptography and proactive updating. We analyze the security of the proposed infrastructure and through simulations we evaluate its performance for various scenarios of untrusted node distributions.     

基于兴趣域的非结构化P2P模型

泛洪式路由（Flooding）是在非结构化对等网络中进行有效资源查找的主要方式,但其路由过程将产生大量冗余消息,因而严重制约了其可扩展性。随节点数增多,泛洪式路由的网络带宽消耗也变得异常严重。针对非结构化P2P网络拓扑的特点,结合对已有的非结构化P2P搜索算法的研究,文章提出了一种基于兴趣域的非结构化P2P搜索算法,使得节点能在短时间内查找到有效的资源,减少了查询信息量,缩短了路由路径,提高了搜索效率。