6 thoughts on “Twenty Questions for the FCC”

  1. Brett has a lot of custom-built and open source tweaks in his wireless routers, and I’m sure rate control is among them. I think part of the issue is that wants to allow occasional FTP and HTTP uploads but not persistent, hours-long random seeding sessions.

  2. Hours-long seeding at 128kbps can’t cause that much congestion on a 10-20Mbps link, although I guess the transit costs could be substantial: 13GB/day. Hmmmm.

  3. Depends how many people are doing it. If you have 20 on one cable segment, you’re going to get a lot of DOCSIS collisions, and if you are one of a small number of providers of a rare file piece, you’re going to have to field a large number of socket opens, each requiring a response.

  4. The problem is more complex than that. There are actually TWO constraints on downstream equipment, whether it’s wired or wireless: bit rate and packet rate. (Due to the overhead in processing a packet, the packet rate becomes important when there are many small packets sent very quickly — such as by a BitTorrent tracker or seeder or by GNUtella’s UDP discovery mechanism. The latter can flood a network with requests for weeks or even months after the machine that was running GNUtella was shut down.)

    It’s also worth remembering that if a user consumes constant bandwidth, it’s a constant and large cost to the ISP. At $100 per Mbps per month, an increment of 128 Kbps is $12.80. Our ISP makes less than $5 per customer per month, so that’s enough to cause a net loss on the customer.

  5. Comcast has a point-to-multipoint network, where the most severe bandwidth constraint is on the upstream side. Consequently, they need to deploy a system that enforces fair queuing among bandwidth requestors. That’s tricky in DOCSIS, as a scheduling decision needs to be made in real time, but it’s not impossible.

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