The idea of using Ethernet throughout the network — replacing Sonet entirely — appears to have vanished, but equipment vendors are still keen on selling the technology as a means of creating services at the network edge. In pre-Supercomm interviews, vendors dealt out anecdotal evidence that carriers have picked up on the idea.

Appian Communications recently announced plans to add Ethernet private local-area network and Ethernet virtual private network services to its Optical Services Activation Platform (OSAP), which comprises boxes that carry both Ethernet and TDM Sonet traffic in native forms.

At Supercomm, Appian demonstrated the new features on rings driven by ONI Systems' metro transport boxes. The OSAP 4800 and smaller OSAP 1600 create dedicated connections that behave like private rings regardless of the topology they traverse. "Think of it as a logical ring that spans multiple Sonet rings, with Ethernet running on that virtual path," said Karen Barton, vice president of marketing for Appian.

The idea is to let carriers add Ethernet services to their TDM rings, rather than build new Ethernet networks. Part of the advantage of a ring is that all traffic flows in one direction, sometimes reversing direction if the way is blocked. The topology is simpler than a mesh, where the exploding number of possible routes requires technologies such as multiprotocol label switching (MPLS) to provide quality-of-service and 50-millisecond restoration for Ethernet.

Appian's preoccupation with rings reflects a common concept in telecom systems: boxes that tap into the existing network. That's always been part of Appian's plan, but other startups during the boom built systems intended to create new networks that would run Internet Protocol in mesh topologies. Carriers' capital budgets have been slashed, however, and it's the existing TDM rings that are the focus for equipment vendors today. Officials at Ethernet vendor Atrica Inc. said, however, that carrier budgets do include room for Ethernet purchases later this year.

"What we're seeing is carriers continuing to solidify their plans for Ethernet," Barton at Appian said.

Other vendors such as Tropic Networks Inc. were quick to point out Ethernet-related applications for their boxes. Tropic's TRX-24000 is an all-optical alternative to an optical add-drop multiplexer (OADM), the system that lets traffic onto and off a Sonet ring.

The system's primary strength is in using passive optical components to send wavelengths on their way, avoiding the use of costly transponders in some cases. But another benefit is the ability to use an existing network to carry Ethernet over Sonet, over MPLS or over wavelengths.

Multiple ways

"There are some carriers that are thinking about deploying three different networks for these three different services," said Ed Dziadzio, Tropic's director of product marketing. "A number of them understand they need more than one way to offer Ethernet to a customer, but they also need to leverage their existing infrastructure."

But the TRX-24000's primary purpose was to reduce the number of transponders needed in the metro network. It uses passive optical components to send wavelengths on their way, as opposed to an optical-electrical-optical step in normal OADMs, which would require transponders to send out the new wavelength.

Another OADM alternative pitched at Supercomm came from Meriton Networks, whose 7200 OADX switches traffic at the wavelength level, with granularity down to 100 Mbits/second, and costs 70 percent less than an OADM, according to David Frost, director of product marketing.