Technologies seem to go in cycles: Every few years, a new technology arises, gets promoted and adopted (or doesn't ... anyone remember SMDS?).

Then a few more years pass as users work out the kinks, economies of scale push down the prices, and the not-so-new-anymore technology gets worked solidly into everyone's business and operational processes.

When it comes to WANs, the cycles are clear: the leased-line/X.25 era of the 1980s gave way to the frame relay/ATM era of the 1990s, which led to MPLS-based services in the 2000s. Meantime, the plethora of competitive network protocols slowly converged on the lingua franca of IP. (Interestingly "pure IP" services never really took off - and today, even though the vast majority of traffic is IP, the networks across which it travels are generally built on MPLS.)

What happens next? For the first time in quite a while, I'm seeing signs of some serious momentum around an emerging technology in the WAN space: carrier Ethernet.

The action kicked off fast and furious back in the spring, when Verizon launched its long-awaited Virtual Private LAN Services (VPLS). VPLS is a carrier Ethernet service based on MPLS, which addresses some of the specific challenges with extending Ethernet across the WAN, most notably scalability and availability.

Although other providers have been offering VPLS services for a while (AT&T has had a limited deployment going for a couple of years, and Masergy was the first to deploy VPLS services in the United States in 2003), Verizon's announcement really marked the most significant commitment by a major US provider.

Another indication: This summer, the Metro Ethernet Forum (MEF) announced that an initial group of global providers had achieved certification for both service functionality and performance - meaning that MEF-certified services are guaranteed to support real-time applications such as VoIP and videoconferencing.

As the name would indicate, the MEF is a global industry alliance comprising telcos, cable companies and a range of other players, with the goal of accelerating the worldwide adoption of carrier Ethernet. Certified providers included AT&T, COLT, Embarq, Neon, NTL Telewest, Optimum Lightpath, RCN, Swisscom, Time Warner Cable, Verizon and VSNL International.

The tests, which were conducted by industry veteran Bob Mandeville, president and founder of Iometrix, demonstrated delays of less than 6 millisecond delay across extended metro areas-enough to handle even the most interactive of applications. And the clincher? Enterprises are getting interested, in a significant way.

More than half of the companies I work with say they're using carrier Ethernet services, or planning to within the next year or so. If you're one of them, make sure to ask your providers about their carrier Ethernet services, and the degree to which they've been certified by the MEF. If you're not, now is the time to put carrier Ethernet services on your road map.