RPR reaches draft standard stage

The IEEE 802.17 Resilient Packet Ring Working Group Friday announced that it has agreed upon a baseline draft of the RPR standard, the first major milestone in reaching ratification, the group says.

The draft, dubbed Darwin to signify an evolutionary merger of two opposing Cisco Systems Inc. and Nortel Networks Corp.-led proposals, received more than 75 percent approval from working group participants during this week's meeting held in Orlando, which ended Thursday evening.

Darwin represents a merger of the Cisco-supported Gandalf and the Nortel-supported Alladin proposals. While the new proposal retains some elements of Cisco's controversial Spatial Reuse Protocol/Dynamic Packet Transport (SRP/DPT) technology, all participants in its development, including Nortel, say the draft represents a true compromise.

"We're really pleased with what we've captured here," says John Hawkins, senior manager of marketing for optical Ethernet at Nortel. "As far as packet format goes, we chose the best of all of them. As far as flexible bandwidth management architecture, we voted on something truly unique to Darwin: We're allowing the end user to decide how to tune his network."

Darwin, according to Hawkins, contains bandwidth management mechanisms presented in both proposals. While Darwin retains the same basic structure for signaling used in congestion as Cisco's SRP technology, changes were made to when and how congestion is detected.

In addition, Darwin's protection mechanisms are a combination of Gandalf's packet wrapping scheme and Alladin's packet steering mechanism. Packet wrapping simply means that packets travel in the opposite direction in the event of a failure. Steering involves notifying all nodes of a failure and subsequently directing traffic away from a fault.

While Gandalf originally proposed using only packet wrapping for protection, Darwin uses packet steering as the default protection mechanism, with packet wrapping as an optional mechanism.

"This really allows us to address all traffic types - toll-quality voice, broadcast-quality video and data," says Raj Sharma, director of Technology Strategy at Luminous Networks Inc. "We accepted the value proposition of both mechanisms and then adapted and evolved SRP to make this work."

Finally, while packet formatting also retains some SRP characteristics, other adaptations have been made, including the addition of a header error-checking field.

"There really wasn't a big to-do about anything," Hawkins says. "It was all a matter of meeting in the middle, and we're all happy about what's been included in the draft."

Luminous' Sharma agrees. "This compromise really shows that the IEEE process has held up again," he says. "I'm confident in saying that this is a fair and complete compromise. Significant changes will be required from all engineers in their product lines, but the real point here is that this draft has remained in line with all of our service ideas."

Bob Love, chairman of the 802.17 working group, warns that there is still much work to be done in the standards process, however.

"A standard is still around 15 months away," he says. "Now is the time to work out all the fine details and make necessary edits. We need to take all of the 17 clauses and formulate them into a single piece of work that will be brought to our next meeting in March."

Jeff Baher, director of marketing for Cisco's Metro IP Access Business Unit, points out that work still needs to be done in the area of topology discovery.

"We tabled these discussions because we hadn't had time to think through it fully," he says. "There are also questions about what speed RPR will be adapted to. We think we're looking to adapt it at 10G bit/sec ring speeds, but that's still in discussion as well."

All in all, the first draft of a potential RPR standard has ended on a positive note.

"There has been a lot of public visibility around this standard," says Mannix O'Conner, marketing executive at Lantern Communications Inc. "A lot of people have been involved in making this decision to compromise and we're very excited. This was our first huge milestone and this is very good news."