SONET vendors pursue Ethernet transport

TECHNOLOGY

By KATHLEEN RICHARDS

Ethernet is the current front-runner for tomorrow's metro data transport. Since the majority of the carriers left standing in the United States operate SONET-based voice networks, technologies that can improve Ethernet transport over SONET were widely displayed at the annual SuperComm trade show in June in Atlanta.

The metro and first mile Ethernet standards are still in the early stages, and operations, administration, management, and provisioning (OAM&P) - issues of particular concern to incumbent carriers-remain either unsolved or tackled using proprietary technologies. Nevertheless, the pros of carrying Ethernet over SONET (low cost, scalability, ubiquitous installed base worldwide) outweigh the cons in the eyes of many in the industry. And every systems vendor that wants to stay in the metro game is getting on board.

That includes SONET maven Fujitsu Network Communications (Richardson, TX), which finally announced support for Fast Ethernet and Gigabit Ethernet (GbE) in its next-generation Flashwave 4500 platform. Last out of the gate among multiservice-provisioning-platform (MSPP) vendors with Ethernet over SONET capabilities, Fujitsu is still well positioned, say analysts, because it has the largest SONET installed base among carriers in North America.

VC and GFP
Competitors, meanwhile, are debuting second-generation products that map Ethernet over SONET more efficiently. These modules use virtual concatenation (VC) schemes that allow finer granularity for bandwidth provisioning, in conjunction with better framing, via the generic framing protocol (GFP). A link capacity adjustment scheme can make VC even more efficient. Fujitsu is expected to announce a product with VC and GFP before the end of the year.

One of several companies that discussed better Ethernet over SONET mapping functionality at SuperComm, Sycamore Networks (Chelmsford, MA) announced an upgrade to its Gigabit Ethernet service module for its SN 3000 intelligent optical switch. The four-port module now supports VC, which allows carriers to offer sub- and full-rate (50-Mbit/sec up to 1-Gbit/sec in 50-Mbit/sec increments) Ethernet services from a single interface. While other companies such as Lucent Technologies, Tellabs, and White Rock Networks also support VC, Sycamore's Bonnie Sitsis, director of product marketing, says Sycamore's module is the first to fully support the G.707 VC standard. The GbE service module is expected to be in production by the third quarter.

"From a technology perspective, the virtual concatenation and GFP does allow more efficient utilization of the SONET bandwidth payload," says Keith Mayberry, optical-networking analyst at RHK (San Francisco). "This second generation of Ethernet mapping to SONET is more efficient based on new silicon capabilities that have been introduced by the semiconductor companies.

"The key thing is how are these next-generation SONET platforms going to be introduced?" wonders Mayberry. "Are they going to be forklifted in and the old systems forklifted out? Or be built on top as an overlay network to what's already out there? The conversations that I've had with some incumbents indicate the overlay model is going to be the one that is used."

However, constrained capital expenditures (capex) may delay the rollout of next-generation SONET. "I think carriers all have these products in labs and evaluations," Mayberry continues. "But a lot of carriers don't have any capex dollars to spend. The capex dollars are tight and probably will get tighter. Deploying these systems in the incumbent networks is something that may not happen this year-perhaps next year." While incumbent local-exchange carrier BellSouth has committed to deploying next-generation MSPPs in 2003, the carrier contends that its required equipment specifications, including the ability to handle full-rate GbE throughput, haven't been met by systems companies.

The demand for Ethernet services remains another question mark. "A couple of carriers that we talked to have not seen the demand materialize," says Mayberry. "While they have customers, the customer volume and the traction are not what they thought they would be for the product."

Staying bundled
As the SONET vendors debut their next-generation systems' Ethernet capabilities, Internet Photonics (Shrewsbury, NJ) is offering a managed Ethernet service solution with "SONET wraparound." It's an optical Ethernet Layer 1 transport offering that allows carriers to preserve their existing SONET add/drop multiplexers and bypass the unbundling regulations that apply to data services over Layer 2 and Layer 3 switches. The solution uses coarse WDM to support Ethernet data transport over its own dedicated wavelength-SONET traffic is carried on other channels-on carriers' existing fiber networks using a ring or a point-to-point configuration.

The LightStack MX, which can multiplex up to eight 1-Gbit/sec services onto a 10-Gbit/sec wavelength, resides in the carriers' point of presence. A carrier-managed system, LightStack MXA, serves as the demarcation point at the customer premises. Integrated OAM&P capabilities allow carriers to manage the Ethernet service end-to-end using an Ethernet control channel that does not mix with the end-user traffic. The LightStack equipment is Telcordia OSMINE-certified and thus managed by carriers' existing network operations centers.

"It is a unique solution that fits right in and doesn't require carriers to forklift the legacy SONET ADMs," says Mayberry, who believes the technology has potential. "They've integrated some management capabilities that fit in with the existing legacy management solutions, so it makes Ethernet provisioning and operations more in line with what the carriers have traditionally been using."

Internet Photonics' approach also allows carriers to incrementally add equipment instead of upgrading an entire SONET ring, which is what is required to offer Ethernet service over SONET to a single customer. Several incumbent carriers have tested the technology, including AT&T Labs and WorldCom. Verizon, SBC, and AT&T have trials in progress.

More in DWDM & ROADM