© 2007 BitTorrent Inc.

Quality of Application:

QoS is Dead, Long Live Politeness

Ben TeitelbaumProduct Marketer, Content Delivery Services

Product Manager, Device Programs

© 2007 BitTorrent Inc.

physics.bigu.edu cern.ch

Quality of Application(s)

QoA

Not just about your application

Multiple apps make up end-user experience

Sometimes doing with less increases overall utility

Design applications1 for the best end-user experience

1. Network matters too, but should not be tuned for specific apps

© 2007 BitTorrent Inc.

Politeness

QoS is dead, but politeness has a long history of success

Ethernet CSMA/CD

TCP congestion control

QBone Scavenger Service (LBE)

throughput ≈ (C x MTU) / (RTT x sqrt(loss))

© 2007 BitTorrent Inc.

QoA at BitTorrent

BitTorrent DNA: peer-accelerated HTTP streaming

• Delivery via CDN ($$$) and DNA peer network ($)

Smart piece-picking

• Maximize peer use while ensuring smooth playback

Painless seeding

• Polite transport protocol defers to TCPs

• Delay-based congestion control anticipates packet loss

• Seeding won’t disrupt gaming, web-surfing, or VoIP

TCP throughput ≈ (C x MTU) / (RTT x sqrt(loss))