ars technica
By Nate Anderson
Full Article
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 do show that P4P's iTracker technology can increase P2P download speeds by 80 percent on ISP networks without materially increasing the network load.
P4P, which is being designed under the aegis of the Distributed Computing Industry Association, is meant to "localize" peer-to-peer 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 just filed the results of the first major P4P trial as an "Internet draft" with the IETF. The trial involved Pando, Yale, three (unnamed) ISPs, and Comcast, and it took place over the summer. 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," in case you were worried), 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 percent above default behavior.
Comcast wants the iTracker mechanism made an IETF standard; more impressively, it recognizes that iTrackers should be "opt-in" mechanisms that each user can control. "The use of ISP-provided iTrackers should probably be an opt-in feature for P2P users, or at least a feature of which they are explicitly aware of and which has been enabled by default in a particular P2P client," say the engineers. "In this way, P2P users could choose to opt-in either explicitly or by their choice of P2P client in order to choose to use the iTracker to improve performance, which benefits both the user and the ISP at the same time."
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.