Investigation of a large-scale P2P VoD overlay network by measurements Bing Li & Maode Ma & Zhigang Jin & Dongxue Zhao Received: 20 November 2011 / Accepted: 12 March 2012 / Published online: 14 April 2012 # Springer Science+Business Media, LLC 2012 Abstract The proliferation of large-scale Peer-to-Peer (P2P) Video on Demand (VoD) overlays has created the demands to characterize and to understand the emergent properties of P2P VoD applications. In this paper, we investigate the P2P VoD overlay network, spanned by PPLive application, using active measurements. We have developed a piece of measurement software, named as VoDCrawler, to implement the experi- ment. Different from other existing work, our study focuses on the topology and the churn of the overlay networks. From the study, we have revealed the major features of the P2P VoD overlay networks and have compared them with those in P2P file sharing and live streaming systems. The discoveries we have obtained could help further investigation of the operation of the P2P VoD systems and favor the commercial develop- ments of the P2P VoD applications. Keywords Measurement . Overlay networks . Peer-to-peer . PPLive . Video on demand 1 Introduction With the development of networks and multimedia codecs, the applications of peer-to-peer (P2P) video on demand (VoD) have become popular in Internet, which work based on P2P architecture to provide the VoD services with much advantage. At one hand, the P2P VoD application is more convenient for users compared with other popular P2P shar- ing service, such as P2P file sharing and P2P live streaming. In the P2P file sharing systems, users have to wait for a long period to download the entire video file before the start of playing. And in the P2P live streaming systems, users can only passively watch the video content playback as the traditional television (TV) users without active interactions and operations on the video playback, such as pause, for- ward seek, backward seek and so on. However, the limita- tions of both P2P file sharing and P2P live streaming systems could be overcome by P2P VoD applications. In the P2P VoD systems, users are allowed to watch the video content after only caching a little part of the video data in their buffers and are able to perform interaction with the video contents according to their interests. At the other hand, compared with traditional VoD applications based on the client/server (C/S) architecture, called C/S VoD, P2P VoD systems could maintain better robustness and scalability. In C/S VoD systems, the capability of servers is the bottleneck of the entire system usually and it is costly to deploy large-scale systems. In contrast, large-scale P2P VoD systems could be easily deployed. In the P2P VoD systems, peers act as both servers and clients and could help to distribute the video data to relieve the stress of real servers. In light of their popularity, the measurements and the analysis of the P2P applications and the VoD applications have become a significant research topic, which could help B. Li : D. Zhao School of Computer Science and Technology, Tianjin University, Tianjin, China B. Li email: leebingice@gmail.com B. Li : M. Ma (*) School of Electrical and Electronic Engineering, Nanyang Technological University, Block S2.2-B2-27, 50 Nanyang Avenue, Singapore 639798, Singapore e-mail: Maode_Ma@pmail.ntu.edu.sg Z. Jin School of Electronics and Information Engineering, Tianjin University, Tianjin, China e-mail: zgjin@tju.edu.cn Peer-to-Peer Netw. Appl. (2012) 5:398–411 DOI 10.1007/s12083-012-0131-0