MEF president Nan Chen, who is also vice president of marketing for Atrica Inc. (Santa Clara, Calif.), presented a summary of the MEF's goals, which have solidified since the forum formed in mid-2001 at the Supercomm trade show.

The MEF is not a standards body itself. Rather, the forum is linking together various standards and definitions to create a reference model for a network that delivers services over Ethernet, regardless of what transport layer is being used.

The key is that the transport layer could be Ethernet itself, Sonet, the Resilient Packet Ring protocol or T1/E1 lines. End users would see applications originating from an Ethernet port but would not know which protocol is carrying those services across the network.

Support for Sonet and other transport types is key because most networks are a patchwork quilt of heterogeneous transport types, said Paul Bottorff, MEF technical committee co-chair and director of switching architecture for Nortel Networks. "The idea that the network will be all RPR or all direct Ethernet or all Sonet is probably wrong," he said.

Moreover, the MEF's ambitions might serve it well in the currently cold telecom environment. Newer service providers such as Yipes and Telseon were creating all-Ethernet networks two years ago, but they've fallen onto hard times. Meanwhile, the incumbent players have chosen to curtail new-equipment spending and concentrate on enhancing existing Sonet or SDH equipment. To gain favor with carriers, metro Ethernet services might have to travel on Sonet highways.

In creating a universal metro Ethernet services layer, the MEF will have to define methods of Ethernet protection and quality-of-service that would apply to any type of transport. That's a lofty goal, so the forum is first concentrating on getting its definitions solidified for pure Ethernet transport, Chen said.

At its August meeting, in Montreal, the MEF completed draft 1.0 of its protection spec. Protection refers to backup paths that the network can use should a particular node or link fail, and it is a critical gap between Sonet and Ethernet. Sonet calls for the network to switch to the backup path within 50 ms, while Ethernet, crafted for LANs, uses a spanning-tree protocol that takes several seconds to complete.

Chen said the MEF would prefer to piggyback on developing standards that use multiprotocol label switching for Ethernet protection. Several such standards have been proposed, however, so the MEF will have to settle on one — preferably one that can work with any transport technology, Chen said. The MEF hopes to have a protection scheme that can be applied across multiple network rings, he said.

MEF members also agreed on draft 2.0 of their Ethernet services definitions, which cover three connectivity types: virtual private lines, Ethernet private LANs and TDM-circuit emulation. Other connectivity services are likely to follow, along with "application services that will sit on top of these," Bottorff said.

Other MEF documents completed in August include Draft 2.0 of the operations, administration and maintenance technical specification and version 1.0 of a user-network interface spec, as well as a draft of the MEF's overall services model.