P2P vs CDN: An
Industry Perspective
Pei Cao
P2P CDNs

With the exception of Skype, almost
all P2P systems are essentially
content distribution networks (CDNs)
• Kazaa, BitTorrent, etc.

The Cost-Transfer Effect: the cost of
content distribution is borne by the
network provider, not the content
provider
• vs. itunes, YouTube, etc.
Legal CDNs

Cache-based CDNs are the most networkefficient delivery mechanism
• the only way to make sure data traverse a link
only once

However, US equipment vendors do not
provide cache support for fear of lawsuits
 Are P2Ps only useful for violating copyright?
P2P for Legal Content

Inherent advantages of P2P over CDNs
• No high initial costs


No cache installations for ISPs
Practically zero cost for content providers
• Supply grows linearly with demand
• End-host driven application-level routing

Many legal content providers want to
use P2P
• Warner Brothers, Apple iTunes (rumored)
Challenges for Legal-Content P2Ps


User demand for QoS = Cost of content to
end user
Challenges for providing QoS
• Research problems:


QoS on top of heterogeneous and dynamic peers
Provide QoS against DDoS attacks
• Need cooperation from network service
provider


Research issue: a way for P2P to be trafficengineered by ISPs
Need a pricing structure
Predictions

Content providers will use peers to
reduce their delivery costs
• as long as the QoS issues are figured
out…

Equipment vendors will cache for
legal peers
• Peers and ISP-based CDNs co-exist and
collaborate

Delivery agreements between
content providers and Cable/DSL
ISPs