TR10: Peering into Video's Future
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Second, ISPs are loath to carry P2P traffic, because it's a big money-loser. For conventional one-way transfers, ISPs can charge content owners such as Google or NBC.com according to the amount of bandwidth they consume. But P2P traffic is generated by subscribers themselves, who usually pay a flat monthly fee regardless of how much data they download or upload.
Zhang and others believe they're close to solving both problems. At Cornell University, computer scientist Paul Francis is testing a P2P system called Chunkyspread that combines the best features of trees and meshes. Members' PCs are arranged in a classic tree, but they can also connect to one another, reducing the burden on the branches.
Just as important, Chunkyspread reassembles files in "slices" rather than blocks. A slice consists of the nth bit of every block--for example, the fifth bit in every block of 20 bits. Alice's PC might obtain a commitment from Bob's PC to send bit five from every block it possesses, from Carol's PC to send bit six, and so forth. Once these commitments are made, no more metadata need change hands, saving bandwidth. In simulations, Francis says, Chunkyspread far outperforms simple tree-based multicast methods.
Zhang thinks new technology can also make carrying P2P traffic more palatable for ISPs. Right now, operators have little idea what kind of data flows through their networks. At his Pittsburgh-based stealth startup, Rinera Networks, Zhang is developing software that will identify P2P data, let ISPs decide how much of it they're willing to carry, at what volume and price, and then deliver it as reliably as server-based content distribution systems do--all while tracking everything for accounting purposes. "We want to build an ecosystem such that service providers will actually benefit from P2P traffic," Zhang explains. Heavy P2P users might end up paying extra fees--but in the end, content owners and consumers won't gripe, he argues, since better accounting should make the Internet function more effectively for everyone.
If this smells like a violation of the Internet's tradition of network neutrality--
the principle that ISPs should treat all bits equally, regardless of their origin--then it's because the tradition needs to be updated for an era of very large file transfers, Zhang believes. "It's all about volume," he says. "Of course, we don't want the service providers to dictate what they will carry on their infrastructure. On the other hand, if P2P users benefit from transmitting and receiving more bits, the guys who are actually transporting those bits should be able to share in that."
Networking and hardware companies have their eyes on technologies emerging from places like Rinera and Francis's Cornell lab, even as they build devices designed to help consumers download video and other files over P2P networks. Manufacturers Asus, Planex, and QNAP, for example, are working with BitTorrent to embed the company's P2P software in their home routers, media servers, and storage devices. With luck, Senator Stevens's tubes may stay unblocked a little longer.