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Broadcasting with BitTorrent - June 26, 2008

BitTorrent president Ashwin Navin has no quarrel with Internet pioneer Vint Cerf's vision of bringing broadcast economics to online video, as Media Wonk reported on in yesterday's post. "Vint was talking about BitTorrent," Navin told me Thursday at the Digital Media Conference in Washington sponsored by Digital Media Wire. "He's been very supportive of our protocol as a way to do point-to-multipoint transmissions. That's part of what BitTorrent DNA is about. It's a way for content publishers not to have to send a million copies of something."

According to Navin, BitTorrent has had about 20 customers beta-testing its DNA service since it was announced late last years. BitTorrent DNA allows content publishers to leverage the 150 million or so PCs worldwide that have installed the BitTorrent client to accelerate the delivery of video to multiple end users.

"The average improvement in server and CDN costs for video has been north of 20%, and in a lot of cases more like 40 or 50%," he said. "For games it's been close to 90%."

The improvement is greater for games because game files don't need to be delivered sequentially, so there's less waiting for particular packets to arrive. Video packets, on the other hand, have to be delivered in the correct sequence for smooth playback, at least at the beginning of a transmission. Once a sufficient amount of video has been loaded into the application's buffer, the need for sequential delivery tails off because packets arrive and can be sorted into the correct order faster than the video is being viewed.

"A lot of what we're working on with publishers is exactly where to set that buffer threshold," Navin said.

On a separate front, Navin said BitTorrent has tweaked its protocol to de-prioritize itself when other applications need bandwidth--one result of its partnership with Comcast announced earlier this year to find ways to better manage the burden placed on ISP networks by upstream BitTorrent traffic.

"Peer-to-peer protocols are designed to consume as much bandwidth as is available," Navin said. "If it's there, they'll use it. That's how they're built.  What we've done is set our protocol to de-prioritize itself if another application, like voice, suddenly needs more bandwidth.

Navin estimates that about 13% of all desktop PCs have the BitTorrent client on them, "and maybe half of those are ones we installed so they've been updated."
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