Grooming grumbling

As providers streamline, expand and adapt their networks, they have become embroiled in a war over the extent to which wavelength grooming should be performed in optical networks.

The debate heats up on the topic of whether granular grooming — down to STS-1 levels, for example — should be performed by optical switches in the network core. While vendors argue their positions based on the type of optical switch — grooming or non-grooming — they have developed, the real question is which works best for service providers.

Tellium has developed the Aurora optical switch, which competitors call a “non-grooming” switch. The Aurora products groom from the OC-48 level and up, but not below it. Tellium's argument is that large service providers typically don't need to groom at more granular levels in the network core.

The Aurora switch grooms 2.5 Gb/s streams into 10 Gb/s channels, said Krishna Bala, co-founder and chief technical officer for Tellium. This creates greater efficiencies in the network because a lot of Sonet equipment can be eliminated, he said. And by performing granular grooming at the network edge instead of the core, service providers should be able to gain efficiencies in the core, which are compounded by the ability to deploy a mesh-based architecture rather than a ring-based one, he added.

“Service providers can get the look and feel of Sonet without the cost and inefficiencies of rings,” Bala said.

Qwest Communications and Dynegy are deploying the Aurora switch.

But all wars have two sides, and Tellium's competitors have different opinions.

One of the main problems with grooming only at the OC-48 level and beyond is that the bulk of the traffic is at the lower levels, said Steve Chaddick, a senior vice president for Ciena, which has taken the lion's share of the optical switch market with its CoreDirector switch. The CoreDirector can groom at OC-48 levels as well as the lower ones, he said.

“Tellium has been relegated to [being] intelligent patch panels,” Chaddick said.

But Tellium's Bala said Ciena isn't a competitor because “they play at the edge with higher granularity.”

Chaddick disagreed. “We do a super-set of what they do and we can do anything they can do,” he said, noting that the Tellium equipment uses an architecture identical to Cisco's now canceled Wavelength Router.

Rick Thompson, Sycamore Networks' director of product marketing, agreed with Chaddick's assessment of Tellium's Aurora product.

“It is almost the exact same as the Monterey switch [acquired by Cisco],” Thompson said, noting the lack of a viable market for the product led Cisco to cancel development.

Sycamore's SN 16000 product grooms down to the STS-1 level. Sycamore considered developing a non-grooming switch a couple of years ago but elected not to because the company didn't believe the market was headed in that direction, Thompson said.

Fueling the grooming debate is market ambiguity. According to Thompson, the subject of grooming is one the industry needs to be educated about. “There is a lot of confusion,” he said.

Much of the confusion centers on the belief that switches grooming at granular levels would be expensive and wouldn't scale. The development of cheaper chips has brought the cost of building a grooming switch down to the same as a non-grooming one, Thompson said.

“Some traffic in the core won't need to be groomed — but only 10% to 20% of it,” he said. “Grooming is a requirement in the core.”