Unreeling Xunlei Kankan: Understanding Hybrid CDN-P2P Video-on-Demand Streaming

The hybrid architecture of content distribution network (CDN) and peer to peer (P2P) is promising in providing online streaming media services. In this paper, we conducted a comprehensive measurement study on Kankan, one of the leading VoD streaming service providers in China that is based on a hybrid CDN-P2P architecture. Our measurements are multi-fold, as follows. 1) Kankan adopts a loosely-coupled hybrid architecture , in which the user requests are handled by its CDN and P2P network independently. 2) Kankan deploys a small-scale CDN densely in three geographic clusters in China. It adopts specific redirection servers to dispatch the nationwide requests. 3) Kankan adopts a dual-server mechanism to enhance start-up video streaming. It also provides the CDN acceleration in case of inefficient P2P streaming performance. 4) According to our studies on the peer cache lists, the video contents stored in Kankan peers update quite slowly. The average lifetime of cached videos is longer than one week. Our results show that, by utilizing the slow-varying contents cached in peers and deploying various CDN enhancement mechanisms , Kankan provides a large-scale VoD streaming service with a small-scale fixed infrastructure. Insights obtained in this study will be valuable for the development and deployment of future hybrid CDN-P2P VoD streaming systems.

I. Introduction

Launched in 2007, Xunlei Kankan¹

[Online] Available: http://www.xunlei.com/

has become one of the leading video-on-demand (VoD) streaming service providers in China with 31.4 million daily unique users in the end of 2012 [1]. In Xunlei Kankan, users are able to enjoy the streaming service for hundreds of thousands of distinct video contents on the Internet including movies, TV episodes and so on. Unlike other existing Internet VoD streaming systems that adopt either content distribution network (CDN) or peer-to-peer (P2P) network for content distribution, Kankan is built upon a hybrid CDN-P2P architecture. A Kankan player requests video segments not only from the CDN servers, but also from the shared caches in peer neighbors. These Kankan clients also form one of the largest P2P networks on the Internet. In a recent measurement study conducted in Jan. 2011, 7.4 million unique peers were observed in one week for just the TV show category [2].