Flow Control for Cost-Efficient Peer-to-Peer Streaming

In this paper we address the issue of network cost efficiency for live streaming peer-to-peer systems. We formalize this as an optimization problem, which features a generic cost function. The latter is appropriate to capture not only ISP-specific link weights, but also non-linear, congestion-dependent costs. Our main contribution is the introduction of the Implicit-Primal-Dual scheme for flow control in live streaming peer-to-peer systems. It is fully distributed in that it relies only on local state variable exchanges. Moreover, we show that at a fluid scale, combined with random linear network coding, it admits the cost optimal operating point as a fixed point. We also prove asymptotic boundedness of fluid trajectories for particular cost functions. We finally show via experiments that these optimality properties are resilient to operational constraints such as finite generation size and finite field size.

I. Introduction

Peer-to-peer systems for live streaming, such as TVAnts and Sopcast, have recently met considerable success. As testimony for this, PPLive, which enjoys over 100 million users, has obtained in 2008 a license from the Chinese government to broadcast media content. Despite this growth and evolution to mainstream usage (as opposed to underground, illegal usage), peer-to-peer systems have recently been facing strong criticisms from ISPs.