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IEEE plots road map for 40/100Gbps Ethernet

Posted: 24 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:IEEE? Ethernet networking? 4100Gbps Ethernet spec?

Arriving at a consensus to pave a road map to both the 40Gbps and 100Gbps options for Ethernet networking, the IEEE is expected to set up an official task group to start writing specifications for these data rates in March next year.

At a San Francisco meeting, the IEEE Higher Speed Study Group decided to support one effort that will draft specifications for 40Gbps and 100Gbps Ethernet. The 100Gbps spec will include versions at 40km and 10km over single-mode fibre, 100m over multimode fibre and 10m over copper cables.

The 40Gbps proposal, mainly backed by companies making data center equipment, was the more controversial part of the decision. Just recently, telecom and networking engineers were at loggerheads over the idea of 40Gbps Ethernet.

Optical transport compatibility
Telecom engineers insisted the speed should be made compatible with existing 40Gbps optical transport networks. Networking engineers did not want to see the 40Gbps speed grade at all, fearing it might fragment the market for high-speed routers and switches, many of which do not have to link directly to optical transport nets.

In the end, all sides agreed to support three flavors of a 40Gbps standard. They include a version extending 100m over multimode fibre, 10m over copper cable and 1m over a backplane. In its documents, the group said the 40Gbps spec will "provide appropriate support for the optical transport network."

"I think the wording leaves the door open to a number of ways to accomplish that goal," said Robert Hays, a strategic marketing manager for Ethernet products at Intel, who was one of the backers of the 40Gbps proposal. "I think one of the fears some people had going into this was that the 40Gbps proposal would be too restrictive," he added.

In side discussions, engineers were able to assure themselves that no one group of companies would bear an undue burden making sure 40Gbps Ethernet is compatible with the optical transport networks. Hays said. "I think everyone felt good about this because we came to an agreement that met most people's needs," he added.

Specifically, engineers informally agreed they will work through groups such as the Ethernet Alliance to educate the market about the different market roles they see for 40G and 100G products. The Alliance is already drafting a white paper on the subject.

The 40G speeds mainly will be directed for use inside or between servers and switches and may not be needed until 2011 or later. The 100G products mainly will link switches in data centers and backbone networks and will be needed much sooner, said Dan Dove, a consultant and former long time employee of Hewlett-Packard's networking division who was active in the IEEE effort.

Dove said networking engineers will work to make sure the final specs do not prevent chip makers from designing silicon that can support both speeds. "We don't want to get into a situation where we have to have double the silicon and twice as many systems," Dove said. He added that having one group write both specs will help drive common technologies into the two data rates.

Encoding question
Still unresolved is the thorny question of encoding schemes. Ethernet is using 64b/66b encoding while telecom companies are proposing approaches such as 512b/513b. Currently, engineers think many of the specs will use multiple channels of 10Gbps Ethernet, especially for short distance requirements. However the issue of parallel versus serial implementations has not been resolved.

If the standards effort stays on track, final specs for the 40Gbit and 100Gbit efforts could be complete before June 2010. Initial draft standards could be hammered out by early 2009, opening the door to some commercial products emerging before the end of 2009.

However, because the group needs to provide a suite of specs for both 40G and 100G, the schedule could be pushed out, said Dove.

- Rick Merritt
EE Times

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