Posts by Jim Summers

Better Analogies

I think the critical point here is that Comcast only resets bittorrent uploads when there is congestion. Assuming they only do it when there is congestion, Comcast really isn't harming anyone, since they only reset when there isn't any spare bandwidth available to upload anyway. When there is congestion, it is better to interrupt protocols that handle delays gracefully, like bittorrent, than to interrupt real-time protocols like VoIP. If Comcast didn't discriminate by traffic type when handling congestion, bittorrent uploads would probably finish slightly faster; but VoIP might be completely unusable.

I think there are two analogies that might help explain the issues.

1. You go to a popular club, but when you try to enter, a doorman blocks you and tells you to wait in line. As patrons leave the club, the doorman allows new people into the club, and eventually you get inside. Did the doorman "block" you or "delay" you? The doorman certainly blocks people from entering, but only when the club is full; so in effect, the doorman is delaying you until there is no congestion.

2. You go to a supermarket, fill your cart, and go to the checkout. You notice a sea of cashiers with long lines in front of them, and resign yourself to a wait. While waiting, you notice that some of the lines are moving much faster than others. You are about to change to one of the fast-moving lanes when you notice the sign: "express lane, 8 items or fewer". As a checkout neutrality advocate, you complain bitterly to the management that if they dropped the restrictions on the express lanes, people with full carts could check out faster. You'll also complain about how counting the number of items in your cart is an illegal invasion of privacy.

In both of these cases, the congestion control mechanisms aren't theoretically necessary; the easy solution is to build a bigger club or hire more cashiers. Also, although the supermarket specifies the rules for the express lane, you don't know for sure why a doorman blocks you, the doorman might be discriminating against you for some other reason. It is better to patronize businesses that are not congested, if at all possible; but it is pretty much unavoidable.

In the physical world, we usually manage to deal with congestion without requiring a bunch of new laws. If a supermarket is always crowded and we can't use the express lane, we'll switch to a different supermarket. If we always have a long wait before getting into a club, we'll switch to a different club. Comcast's networks are regularly congested, so much so that it was worth adding equipment just to make the congestion more bearable. If you don't like Comcast's congestion or how they mitigate that congestion, switch to an ISP who makes better tradeoffs; I don't think it is necessarily a better solution to force all ISPs to use the same congestion control algorithms (or none).