Comcastic P4P: 80% Speed Boost for P2P Downloads

Excerpted from Ars Technica Report by Nate Anderson

Comcast engineers have just released the first-ever real-world data on P4P technology - and it appears to be a massive success. While only a trial, the results show that P4P’s iTracker technology can increase P2P download speeds by 80% on ISP networks without materially increasing the network load.

P4P, which is being designed under the aegis of the Distributed Computing Industry Association (DCIA), is meant to “localize” peer-to-peer (P2P) transfers. P2P users generally grab data from all around the world, putting tremendous cost and bandwidth pressure on ISP peering and transit links with other networks.

P4P uses an iTracker server to keep those transfers within an ISP’s own network when possible, with the goal of boosting speeds for users and lowering peering-point loads for ISPs.

Comcast engineers have filed the results of their first major P4P trial as an “Internet draft” with the IETF. The trial involved Pando Networks, Yale University, three other ISPs, and Comcast.

It used a special, Pando-provided P2P client that is set up to check in with “iTracker” servers when searching for download locations in a BitTorrent swarm. The test used a 21MB video file (which was licensed), and measured the results of using the P2P client in order to see how the use of iTrackers affected uploads and downloads.

Results were hugely positive. Compared to a random swarm, the use of any iTracker provided substantial speed boosts to Comcast network users, ranging from 57 to 85% above default behavior.

Further good news came from a close examination of the various iTrackers. The fine-grained tracker provided detailed topology information about Comcast’s network, and it took significant time to set up. “It was a detailed mapping of Comcast backbone-connected network Autonomous System Numbers (ASN) to IP Aggregates which were weighted based on priority and distance from each other,” says the report.

Win/win scenarios haven’t been common in the P2P wars, and it’s important to note that this was only a preliminary test. But if P4P shows the same promise in larger trials and if P2P clients start to embed the technology into their software, faster downloads and lower-traffic peering points could be had simply by running some inexpensive servers.