Despite its checkered past, there is new proof that Resilient Packet Ring technology, which provides a efficient and highly reliable mechanism for deploying Ethernet services in a fiber ring, is catching on with service providers (see RPR: RIP? and RPR: Deadlock Ahead?).

“I remember saying RPR was dead last year,” says Michael Howard, a principal analyst at Infonetics Research Inc. “But surprisingly carriers are very interested in it."

Indeed, big carriers are starting to roll out services based on the technology, and many more say they plan to use it in their networks next year.

Earlier this week, AT&T Corp. (NYSE: T) announced it would be deploying RPR-enabled gear from Nortel Networks Corp. (NYSE/Toronto: NT) to offer its AT&T Ultravailable Managed OptEring Services (see AT&T Expands Ethernet). This service leverages RPR technology to transport data, packet video, and voice-over-ring topologies. It will enable business customers with multiple locations in a metropolitan area or campus environment to interconnect sites as a private or virtual local area network.

According to a recent Infonetics report called "Service Provider Networks: Access, Routing, Switching, and Optical, US/Canada 2002," 13 percent of the North American carriers surveyed say they now use a pre-standard version of RPR. About 25 percent say that they are willing to use a pre-standard version of RPR in their networks, and 19% percent say they plan to use the standard version when it’s available next year.

“We’ve seen a lot of interest from our customers who want services that only RPR can deliver,” says Andrea Chiaffitelli, a services director at AT&T. “Nothing else is available that can provide the same level of protection switching necessary for carrying critical assets.”

The AT&T announcement is important on two fronts. For one, this is one of the largest RPR deployments to date. AT&T is deploying Nortel's Optera Metro 3500 switches in up to 70 metro area networks in 38 states throughout the country. The service is currently running in a controlled trial in New York City, with other rollouts soon to follow. AT&T already provides optical Ethernet services to businesses on private, dedicated infrastructures.

Nortel Networks Corp. (NYSE/Toronto: NT) and Cisco Systems Inc. (Nasdaq: CSCO) have been shipping pre-standard versions of RPR on their gear for over a year now. Nortel has deployments at KDDI Corp. in Japan as well as Bell Canada (NYSE/Toronto: BCE) and Bell West in Canada. But this is one of the largest deployments out there, says Jim Dondero, director of optical Ethernet solutions for Nortel.

The second important aspect of this announcement is that AT&T will be using a version of the technology that is as close to the upcoming standard as possible. Up to this point, RPR deployments have involved only proprietary versions of the technology. Even the AT&T implementation is not truly standards-based, since the standard will not be finalized until next year. But Nortel is using specifications from the latest Institute of Electrical and Electronics Engineers Inc. (IEEE) 802.17 draft, which has already been submitted for review and voting by the working group (see RPR Alliance Reaches Working Ballot). The content of the draft is not expected to change significantly between now and the third quarter of 2003, when it will likely be finalized by the IEEE (see RPR Gurus Set Fall Deadline).

Many in the industry are looking at AT&T’s announcement as a big step forward for RPR.

“I take the AT&T announcement as a huge endorsement of RPR, and this endorsement has occurred well in advance of the Standard's approval,” says Robert Love, president of the Resilient Packet Ring Alliance. “It shows that once the carriers are comfortable that the technology will be standardized, they are not that reluctant to begin their rollout.”

In particular, it seems carriers are more comfortable deploying the Sonet-based version of RPR than the version that runs Ethernet over fiber (see Resilient Packet Ring Technology). In the Ethernet-over-Sonet model, carriers use Sonet for transport, and they use RPR to more efficiently utilize fiber, using a special protocol called spatial reuse. RPR proponents argue that this is more cost-effective than pure Sonet implementations. RPR also provides sub-50 millisecond restoration, making its protection comparable to Sonet's.

“Carriers that like rings and already have rings can conveniently ride RPR over existing Sonet/SDH rings,” explains Howard. “They are not choosing the RPR-over-fiber version, rather the layer 2 RPR over layer 1 Sonet/SDH.”

Indeed, AT&T is deploying the Sonet version of the technology. AT&T's Chiaffitelli says that it fit the requirements of AT&T’s network more closely than the purely Ethernet version of the technology.

“We’re targeting customers that might already have Sonet rings, or they are using DWDM,” she says. “Ethernet over RPR offers a way to complement those services.”

— Marguerite Reardon, Senior Editor, Light Reading