Comcast: P4P up to 80 percent faster for P2P downloads at same load

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. For consumers, this would obviously be welcome news, but how does it affect Comcast?

Not too much, it turns out. "We did notice that download activity in our access network increased somewhat, from 56,030MB for Random to 59,765MB for P4P Generic Weight and 60,781MB for P4P Coarse Grained," wrote the Comcast engineers. That's a small increase, especially given that it reduced Comcast's "incoming Internet traffic by an average of 80 percent at peering points."

But uploads proved even more surprising. "It did not appear that P4P significantly increased upstream utilization in our access network," note the engineers. "In essence, uploading was already occurring no matter what and P4P in and of itself did not appear to materially increase uploading for this specific, licensed content."