Understanding the impact of VCR operations in P2P VoD systems

One of the main challenges faced by peer-topeer (P2P) video-on-demand (VoD) systems is their ability, or lack thereof, to provide VCR functionality (e.g. random jump operations). Such jump operations can have special impact in the server load during flash crowd events, since the server is the only node in the system with a full copy of the video. Currently, there is little knowledge of the impact that such VCR operations can have in the swarm efficiency (and therefore in the playout rate and start-up delay), as well as in the server’s load under different jumping and arrival patterns. In fact, existing state-of-the-art approaches rely mostly on highly over-provisioned peers and servers to absorb such jumping operations. In this paper, we provide the first evaluation of the impact that VCR operations can have on P2P VoD systems for various arrival and viewing patterns. We provide both analytical evidence and experimental results. To better evaluate the impact of these patterns, we have built a system called Kangaroo, which provides advanced DVD-like features, namely arbitrary forward/backward jumps, using an entirely mesh-based network. The system achieves its goals through a combination of carefully designed mechanisms, including proper block scheduling algorithms and peerneighborhood topology management. We also study how viewing patterns affect the performance of the system and use traces captured from a live VoD system, to characterize the performance of the system under realistic workloads.