Metro Ethernet cruises toward mainstream

"Now that we've gotten beyond the experimental phase, we need to get products that are interoperable," said Stephen Trowbridge, who is vice chairman of the study group working on the ITU standard and an engineer at Lucent Technologies. "It can't matter whether you have a Nortel box on one end and an Alcatel or Lucent box on the other. Carriers need standards."

Developed 30 years ago, Ethernet is the predominant technology used to connect computers on a corporate network. Now, carriers are using the technology to connect multiple corporate networks together in a metropolitan area network. Over these Ethernet connections, companies can mix their voice and data traffic over a network using Internet Protocol.

Ethernet allows carriers to offer more flexible services. For example, customers can specify how much bandwidth they want within the range of 10 megabits per second and 1 gigabit per second.

Metro Ethernet, as it is called, is also expected to save carriers money. Telephone companies could cut their operating costs by 23 percent annually by using Ethernet services in their metro networks rather than traditional telecommunications services, according to a study released in January by PointEast Research and the Metro Ethernet Forum, a marketing group made up of equipment vendors and service providers.

Traditionally, carriers have connected corporate networks together using other technologies, such as Frame Relay and ATM (Asynchronous Transfer Mode). These services typically run over an optical transport technology called SONET/SDH (Synchronous Optical Network/Synchronous Digital Hierarchy). The new specifications announced last week by the ITU, a global standards group, provide a standardized way for mapping Ethernet over the existing SONET/SDH infrastructure.

Pure Ethernet works fine on a corporate network, but the technology lacks sophisticated, built-in mechanisms for trouble-shooting that are already available in SONET/SDH, said Trowbridge.

For example, SONET/SDH, which is deployed on fiber rings, is able to detect and recover from an outage within 50 milliseconds. Ethernet doesn't have this self-healing feature and relies on Internet Protocol to restore service. In a large network, this can often take several seconds. Some vendors have tried to add new features to Ethernet to make it more reliable and easier to troubleshoot. But others have layered Ethernet on top of SONET/SDH technology, so that carriers can use their existing infrastructure.

"Ethernet over SONET/SDH is a more realistic solution for the operator environment," Trowbridge said. "And today, pretty much every equipment vendor out there sells SONET/SDH gear with Ethernet interfaces."

Several equipment makers, including Cisco Systems, Lucent and Nortel Networks, have already developed products for this market. In fact, equipment makers sold about $2.9 billion worth of metro Ethernet gear in 2003, according to Infonetics Research.

The market is expected to grow to roughly $7.5 billion in 2007, the research company said. It also predicts that more than $24 billion will be spent worldwide on Ethernet in metro networks between 2003 and 2007. Standards such as the ones developed by the ITU should help spur adoption among carriers because they will ensure that products from one vendor will interoperate with another's.

The ITU isn't the only organization working on new standards for carrier-grade Ethernet. The Metro Ethernet Forum has come up with a set of standards describing how certain services are handled over a metro Ethernet infrastructure. And the Institute of Electrical and Electronic Engineers has developed definitions and specifications for equipment running Ethernet in metro networks.