In the so-called backbone of the telecommunications system, the fat pipes that pour data across continents, the name of the game is raw speed (see "Building a Better Backbone,"). But the data racing through the telecom backbone can't fulfill its mission until it is shuttled through the "metropolitan loop," a complex network of cables and switches that delivers those bits to businesses, factories, schools and homes. It's there that the information gusher narrows to a relative trickle, because the metro loop is every bit as tangled as downtown rush-hour traffic. If the broadband revolution is ever to be a reality, the metropolitan bottleneck must be broken.

But that's a tall order. Upgrades in the metro loop have been far slower in coming than advances in the backbone. The reasons range from tougher cost constraints to urban bureaucracy to the presence of a patchwork telecom infrastructure dating back to the 1970s and '80s. But R&D aimed specifically at the metro loop is slowly pushing a variety of solutions out of the laboratory and under the streets. And if we really want broadband, those fixes had better work.