YouTube traffic dynamics and its interplay with a tier-1 ISP

Abstract

In this paper we conduct an extensive and in-depth study of traffic exchanged between YouTube data centers and its users, as seen from the perspective of a tier-1 ISP in Spring 2008 after YouTube was acquired by Google but before Google did any major restructuring of YouTube. Using flow-level data collected at multiple PoPs of the ISP, we first infer where the YouTube data centers are located and where they are connected to the ISP. We then deduce the load balancing strategy used by YouTube to service user requests, and investigate how load balancing strategies and routing policies affect the traffic dynamics across YouTube and the tier-1 ISP.The major contributions of the paper are four-fold: (1) we discover the surprising fact that YouTube does not consider the geographic locations of its users at all while serving video content. Instead, it employs a location-agnostic, proportional load balancing strategy among its data centers to service user requests from all geographies; (2) we perform in-depth analysis of the PoP-level YouTube traffic matrix as seen by the ISP, and investigate how it is shaped by the YouTube load balancing strategy and routing policies utilized by both YouTube and the ISP; (3) with such knowledge, we develop a novel method to estimate unseen traffic (i.e. traffic that is carried outside the ISP network) so as to complete the traffic matrix between YouTube data centers and users from the customer ASes of the ISP; and 4) we explore what if scenarios by assessing the pros and cons of alternative load balancing and routing policies. Our study sheds light on the interesting and important interplay between large content providers and ISPs in today's Internet.