By Jeffrey Krauss,
Bandwidth Monitor
and President of Telecommunications and Technology Policy
For months, bandwidth hogging by peer-to-peer (P2P) services has been the talk of the town, but now, network operators have started doing something about it.

With P2P file sharing, you can use your computer to download music and video files from other computers attached to the Internet. There is no central repository of files. The files reside on computers just like yours. In fact, so long as your computer is attached to the Internet, others can download files from your computer.

How do you know where to find the file you want? You search. There are three approaches to this. Napster provided a central registry for all shareable files–very efficient, but vulnerable to being shut down by the copyright owners. Gnutella uses a decentralized approach, and your computer must send out search messages that are relayed from peer to peer to peer–very inefficient and slow. KaZaA uses an intermediate approach. Some computers become ultra-peers, and each establishes a registry of information about the computers "connected" to it. Except these are logical connections, not physical, so the physical path between your computer and its ultra-peer might involve many network hops.

Recent studies suggest that more than 50 percent of Internet traffic is P2P file sharing. According to Time Warner Cable, 12 percent of subscribers use 80 percent of capacity. And on some ISPs, up to 70 percent of upload traffic is P2P!

There are several strategies for dealing with this. Bandwidth-shaping technology allows network administrators to establish priorities and give certain applications like e-mail preference over others. They can also limit the amount of bandwidth that P2P applications can consume. New products that make this feasible are claimed to be very accurate in detecting and limiting certain protocols and types of traffic, while allowing other types of traffic to flow freely.

Detecting P2P traffic is possible because P2P packets contain certain signatures in the form of bit patterns that identify themselves. But protocols evolve over time, and the protocol used by KaZaA today is different from the one it used last year. So bandwidth management vendors have to monitor the P2P software and incorporate periodic updates into their products.

While it's possible to block all P2P traffic, a less drastic approach is to limit the available bandwidth. For example, earlier this year, at the request of Towson University, Comcast implemented rate limiting to limit the bandwidth used for P2P file sharing on the college dorm network. But the university didn't disclose how much bandwidth would be available for P2P, or whether it would vary by time of day or differ by uplink or downlink.

Another approach is to try to intimidate your subscribers. Last November, one cable modem ISP, Prolog (Palmerton, Pa.), operating on the Service Electric cable systems, notified its subscribers that it has a policy prohibiting residential users from operating servers. It said that allowing P2P uploading from your computer is a prohibited server activity. But no enforcement action has been taken, so far as I can tell. Similarly, Cox is sending warning letters to users who exceed a download cap of 30 gigabytes per month. But nobody has been kicked off.

One company, Sandvine Inc., has a different idea. Because the P2P search process doesn't care what a download costs in terms of network resources, there is no incentive to fetch the file from a computer that is nearby. For an ISP, the cheapest way is for one subscriber to retrieve the file from another subscriber to that same ISP, using no external resources at all. The Sandvine equipment analyzes all P2P searches and ensures that each is redirected down the least-cost network path. It finds the copies of the file you want, and downloads it for you in the most efficient way. In other words, it becomes a participant in the P2P activity. Your lawyers might find that a little scary.

Any of these bandwidth management approaches might run afoul of some franchise agreements. A few months ago, the County Council where I live (Montgomery County, Md.) amended the cable TV law. The original version of the amendment contained detailed technical requirements such as:

Cable modem service must provide and maintain download capacity of at least 3 GB in any 24-hour period, and must provide and maintain upload capacity of at least 2 GB in any 24-hour period.

But at the last minute, those technical details were deleted, and the following language was added instead:

The County Executive must issue regulations…establishing minimum cable modem service levels that a franchisee must provide.

Of course, the FCC decided that cable modem service is an information service and not subject to cable franchise regulations, and we all hope the Court will agree.

But the best approach is what Time Warner is trying. In three systems, TW has created a higher tier called Road Runner Xtreme. Users who exceed the download level of 15 GB per month will pay more, either by joining the higher tier that allows 40 GB per month, or by paying a surcharge for every 5 GB above the 15. That sounds good to me. I've been subsidizing those hogs. Let them pay more. And, oh yeah, give me a discount.

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