Resilient Packet Ring Standard Set to Put Vendors on Course

The IEEE's 802.17 Working Group closed out its January meeting in Orlando with completion of a first draft of the resilient packet ring standard, putting vendors on course to be delivering standard-compliant products for beta trials by year's end.

"We left our meeting in Orlando [in late January] feeling very excited that we'd hit all of the milestones we set when we began this process over a year ago, including the big one, which was to get a first draft completed by January of 2002," said Bob Love, chairman of the Reslient Packet Ring Alliance (www.rpralliance.org) and vice chairman of the 802.17 Working Group.

Resilient packet ring (RPR) technology is designed to allow both traditional TDM (time division multiplexed) and packet-based services to flow over the same optical infrastructure in a more bandwidth-efficient manner than can be done with Sonet alone. However, it is compatible with Sonet in the sense that RPR optical restoration and rerouting can be done in conjunction with use of Sonet framing to carry essential network management information.

For example, Ethernet over RPR makes more efficient use of existing Sonet ring infrastructure by using bandwidth in both directions, rather than just one, while leveraging Sonet link protection to provide less than 50-millisecond failover.

Officials described the draft framework as a triumph of compromise in the direction of accommodating all sector needs in what often has been a contentious battle among vendors and service providers pursuing a variety of application optimized approaches. The group even managed to meet the requirements of cable operators, who lately have looked on RPR as an attractive way for them to route multiservice traffic over their metro backbones, noted Raj Sharma, director of strategic technology at Luminous Networks Inc. (www.luminous.com).

"RPR provides a way for cable operators, who traditionally deliver services in a point to multipoint configuration, to set up dedicated interactive service paths without having to build a mesh network where you have to replicate all the point-to-multipoint traffic over each link," Sharma said.

The trick, he added, was to make sure that, in the case of network failure, rerouting on the ring didn't result in delivery of point-to-multipoint signals to different hubs out of synch with each other, which could create unacceptable levels of jitter.

This meant that something called "bandwidth steering" had to be used, versus the Sonet-like process of "wrapping," where any given optical ring is wrapped to another so that, in the event of failure, the signal reverses course and travels over the backup ring to its destination in the opposite direction.

Steering avoids the long delay that can be incurred by going completely around the ring to get to a point relatively close by redirecting signals from the point of entry onto the network, thereby shortening the distance traveled to the most distant node from the point of failure.

"Over time people realized there were benefits with both options," said Gady Rosenfeld, director of strategic marketing for Corrigent Systems Inc. (www.corrigent.com). "With wrapping you minimize packet loss, while steering minimizes jitter. So the SP can implement whichever approach works for its services, with steering set as the default in the draft standard."

The draft 802.17 specifications reflect many such compromises that provide a wide range of multiple options for implementation of RPR capabilities, Sharma noted. For example, he said, the add/drop functionalities at each node can be tailored to a mode of operation that either gives complete priority to the traffic stream flowing over the ring, or it can be set to assign priority to incoming traffic over traffic elements in the passing stream, based on the quality of service parameters associated with each.

Another significant area of compromise in bandwidth management has to do with including "knobs" that allow service providers three different approaches, Sharma said. These range from absolute guaranteed QoS to best effort, with a flexible pro-rata assignment of bandwidth based on service level agreements as the middle ground.

The 802.17 Working Group hopes to get to the point of issuing a draft for working group ballot following its plenary meeting in July, which should lead to eventual final approval in a sponsors' ballot by early next year. By year's end vendors should be in a position to deliver standard-compliant products for testing, with any final refinements incorporated in time for commercial rollouts at about the time the standard is officially sanctioned sometime next March, Love said.

"We see RPR as the ideal vehicle for carrying Ethernet," he added.

Luminous, in mid January, achieved one of its biggest wins with the RPR product it has been offering in advance of standard completion. China Netcom Corp. (www.cnc.net.cn) said it has begun generating revenues over its newly deployed Luminous platform with a range of customers that includes the Shanghai stock exchange. The carrier is delivering TDM circuit voice as well as data traffic over the RPR networks in nine cities spanning five provinces, said Charelson Zheng, COO at China Netcom.

"This solution has given us the flexibility to offer all our voice and data services on one efficient metro platform, and our customers are responding," Zheng said. "In Shanghai, 100 customers signed up within one week after the equipment was installed."

Another major success for RPR networks in the pre standard phase was recorded in Asia recently by Nortel Networks (www.nortelnetworks.com) in a deal with KDDI (www.kddi.com) of Japan. KDDI said it was going to deploy Nortel's OPTera Metro 3500 Multiservice Platform and OPTera Packet Edge System to create what is expected to be Japan's first carrier-grade optical metro rings using optical Ethernet over RPR technology.

"We're working closely with KDDI to help them address the e-Japan initiative, which aims to make Japan the world's most advanced, IT based knowledge nation within five years," noted John Giamatteo, president of Nortel Networks Japan.

The new metro optical rings represent the first phase in KDDI's metro network expansions, which are leveraging off a Nortel-supplied 1.6tbps capacity DWDN (dense wave division multiplexing) intercity backbone the carrier has been deploying over the past year.

The next-generation Ethernet platform puts KDDI in a position to go well beyond the traditional Ethernet services mode, allowing the carrier to do such things as automatically provision services to multiple end points for any given end user in a point- to-multipoint array; provision multiple users with individually managed 10mbps or 100mbps feeds from an edge point served by a gigabit Ethernet link; and offer end-to-end service level guarantees that were previously impossible.

Such capabilities add up to enabling SPs to leverage the low cost and simplicity of "connectionless" networking with the reliability, scalability and capacity of optical to deliver increased bandwidth directly to customer premises, Giamatteo said.

"In densely populated cities, this means bringing content and information directly to enterprises via very high-speed broadband, dramatically increasing productivity by enabling faster and greater access to data and applications," he said.

The implications of such developments for how voice services as well as data services are positioned and sold are profound. A cost-driven method of doing things at broadband levels of speed and quality on a par with 10 and 100mbps LANs will affect everyone in the channels, as well as carrier spaces, especially insofar as intra-office private-line voice delivered over IP packets in wide area Ethernet connections incurs no PSTN cost add-ons.

Now that the technology platforms are making it possible to provision services on a mass-market basis, the demand for the efficiencies surrounding Ethernet services could go a long way toward reinvigorating the global flow of traffic.

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