Herding BitTorrent Traffic away from Expensive ISP Links UMass CMPSCI Technical Repor UM-CS-2008-036

The steady increase in access link capacity of broadband subscribers coupled with the significant increase in traffic, partially due to popular peer-to-peer (P2P) file sharing applications, has had an adverse economic impact on last-mile Internet Service Providers (ISPs). Reducing the cost associated with P2P traffic has become a major issue for ISPs worldwide and has triggered several proposals. However, previous works advocate for changes to P2P software or require application-specific packet identification and manipulation. This paper presents a distinct approach. We leverage on the observation that traffic costs can be reduced by diverting traffic away from expensive links and into cheaper links. We focus on BitTorrent (BT) traffic and propose a change to the ISP’s access router packet schedulers in order to divert traffic away from links labeled as expensive by the ISP. Our proposed packet scheduler is stateless. Our approach requires no change to applications, is blind to packet payload, and only requires changes to access routers of ISPs that desire to reduce their BT traffic costs. Our simulation and experimental results indicate that our approach can successfully herd BT traffic towards cheaper links (up to 50% reduction), without sacrificing user-level performance.