Protocol Wars have raged in the network design community since the 1970s, or as long as we’ve had packets to switch. In many ways, the current debate over Internet regulation (AKA “net neutrality”) recaps those debates, albeit in a much more foolish way as the loudest voices are the most ignorant. Dana Blankenhorn spills the beans on the article of faith that motivates the regulators:
The idea of absolute top-down control in any area — entertainment, business, technology, politics — is simply non-optimal. Technology has enabled us all to be participants, in any way we wish to be, as well as audience.
That’s heavy, isn’t it? And true! Or not.
“Absolute top-down control” sounds like a really horrible thing, but so does “absolute bottom-up chaos”, because the two most hysterical terms are the first and last. Strip them off and you simply have “top-down”, a pretty respectable concept in many settings. Functional families are managed top-down, and so are businesses, nations, all social groups of animals, etc. So what’s the problem?
Top-down systems are quite often the optimal solution to engineering problems, as they eliminate from the get-go the fundamental problem with edge-managed or bottom-up systems: flapping. If you have four selfish people in a taxi, each of whom wants to get to a different place as quickly as possible, and they can all bark orders at the driver, you may never get anywhere, you’ll simply go around in circles until you run out of gas. All complex systems revolve around compromise, and the top-down control system is in a good position to assess general benefit and ensure that it’s allocated appropriately. It doesn’t scale well, and that’s where modularity and segmentation kick in.
The classic example in networking is the Ethernet. As originally conceived, it was a completely decentralized system, where all decisions about who got to transmit when were made by contention. Each system listened to the wire until it was silent, and then started transmitting. If two systems transmitted at once, they both noticed the collision of their packets and backed-off. After a semi-random delay, they tried again. Eventually everybody got to transmit, but the delays could be substantial. So along comes the Ethernet re-design, where the decision about who gets to transmit is moved up a level, to the switch. Everybody can transmit anytime the switch says they can, and the switch allows several systems to submit packets at the same time, which it sorts out as bandwidth becomes available. Switched Ethernet is centralized, and capable of using 100% of network bandwidth without losing a millisecond to collisions, backoffs, and dead time. It’s the optimal system, and that’s why you use it today.
In this as in many instances, absolute top-control is more optimal than absolute bottom-up chaos. And better than both is moderate top-down management, driven by a policy of the greatest good for the greatest number, or some similar rule.
As an example of engineering fact, it could well be that the best design for a network that permits all people to be performers is for the network’s tubes to be controlled top-down in the interest of fair access. Some at the edges are spammers, virus-makers, and other low-lifes. Can we always count on them to police their own behavior? I don’t think so, and neither do you.
So why do so many grown men still repeat the most idiotic sayings of the scruffy hippies of the 60s?
It’s a great mystery to me.
H/T Doc Searls.