Ethernet definitely simplifies the network, and if you're talking about switched Ethernet, you eliminate the scalability problems associated with routers. A secondary argument, though scarcely less forceful than the first, emphasizes the significant cost differential between limited production Sonet and ATM infrastructure equipment, on the one hand, and the ubiquitous Ethernet switches and routers, on the other, and suggests that for the competitive carrier attempting to undercut incumbent pricing, gigabit Ethernet is the only logical approach. Ethernet gear is cheaper, so the argument goes, by at least an order of magnitude than Sonet and ATM equipment of comparable speed, and economies of scale in favor of Ethernet will only increase the price discrepancy in the future. Ethernet equipment is much cheaper than Sonet or ATM gear, and is very appealing on those grounds. Dave Schaeffer, CEO of Cogent Communications, a metropolitan provider of high-speed access over fiber utilizing gigabit Ethernet over Sonet, agrees entirely with the price argument.
Ethernet is driven by commercial pricing and volume sales.
Equipment that is specifically oriented to carriers is always going to be much more expensive. Tim Dixon, vice president of marketing for Calient, a manufacturer of MEMS switches and other optical components, while admitting that the day of pure Ethernet may well lie several years off, sees still other trends favoring a transition away from circuit-based Sonet or ATM infrastructure in the metropolitan networks. IP is already establishing itself in the long haul. You have companies like Enron that aren't using ATM at all anymore. The multiprotocol lambda switching protocol is intended to provide that functionality by extending the QoS provisions of MPLS from the edge router to the lambda router at the core.