Volatility of YouTube content in Orange networks and consequences

We report in this paper traffic measurements of YouTube traffic from Orange networks. We specifically analyze two weeks of measurements in early April 2012. We show that the popularity curves of YouTube files are constant in time and can be well approximated by truncated Zipf laws with a shape parameter less than one. In addition, there is a huge number of files which are viewed very rarely (only once or twice). Even if this may appear as an unfavorable situation with regard to caching in view of theoretical results on cache systems, we show that thanks to file request dynamics caching is very efficient for YouTube traffic. The main reason is that files are massively requested in bursts. Since these bursts represent a significant part of traffic, caching files even by using a rather small storage capacity can achieve high gains in terms of saved bandwidth. Bursts are moreover sufficiently intense so that popular files are not pushed out of the cache memory by those files viewed only once or twice. These observations are illustrated by performing trace driven simulations by using traffic traces captured in the Orange IP backbone network.