The next Ethernet speed will be 100Gbit/s, the IEEE voted recently. Now the standards body just has to go build something never done before.

The IEEE's High Speed Study Group (HSSG), tasked with exploring what Ethernet's next speed might be, voted to pursue 100G Ethernet over other considerations, such as 40Gbit/s Ethernet. The IEEE will work to standardise 100G Ethernet over distances as far as 6 miles over single-mode fibre optic cabling and 328 feet over multimode fibre.

With the approval to move to 100G Ethernet, the next step is to form a 100G Ethernet Task Force to study how to achieve a standard that is technically feasible and economically viable, says John D'Ambrosia, chair of the IEEE HSSG, and scientist of components technology at Force10 Networks.

"There is still a lot of work to be done to finalise our objectives, and where this thing will go," D'Ambrosia says, adding that a formal task force could be approved by July 2007. A completed 100G Ethernet standard might appear by 2009 or 2010. "The next step is getting the project into the 802 process," he adds, referring to the IEEE's umbrella of Working Groups for networking standards, which govern everything from wired Ethernet and Token Ring to wireless LANs and WiMAX.

The need for 100G Ethernet is growing as IP video and transaction-intensive Web 2.0 applications are exploding across the Internet. Companies such as YouTube regularly add 10Gbit/s service pipes to meet growing demand, and carriers will need a better way to aggregate such links, industry watchers say.

The challenge for 100G will be to push Ethernet to a megabits-per-second speed that does not currently exist under any standard. Examples of past leaps in Ethernet speeds, which followed the lead of other technologies include: Fast Ethernet, followed the 100Mbit/s FDDI standard; and 10G Ethernet, which used the 9.9Gbit/s OC-192 SONET as its base. In each case, resulting Ethernet standard borrowed components and encoding techniques used in the existing non-Ethernet standards.

While a comparable 100Gbit/s standard does not exist now for Ethernet to emulate, D'Ambrosia anticipates this will not be too great a challenge for work on 100G. A 100G standard will probably use parallel data transmission -- multiple 10Gbit/s-plus signals travelling over multiple fibres or lanes, D'Ambrosia says. "There has been a lot of maturing in 10G technology" around bonding together multiple links, D'Ambrosia says. "Everyone [in the HSSG] has a high comfort level that we can leverage existing technology" to achieve a 100G standard.

A recent multi-vendor demonstration showed one possible implementation of this kind of parallel 100G Ethernet. The test involved a pre-standard 100G Ethernet protocol stack, which bonded together 10 10Gbit/s links and transmits them over separate optical wavelengths.

Compared to the current standard for link aggregation the 100G demo was "similar but different," says Serge Melle, vice president of technical marketing for Infinera

"Link aggregation groups allow you to group multiple 10G channels together, but this has limitations on scaling," because a total of eight links can be bonded, Melle says. "What we demonstrated is truly a 100G at the MAC layer."

The demonstration was conducted using a Xylinx field-programmable gate array (a software-programmable chip), which acted as the physical 100G Ethernet MAC layer. Traffic from this layer was transmitted to Finisar short-reach optical transceivers, which split the signals into 10 different 10Gbit/s dense wavelength division multiplexing wavelengths, sent over Infinera DWDM gear. At the other end of the link, the 10 separate wavelengths were reassembled so that that transmission appeared as one logical data flow. Level 3's optical network was used in the demonstration, which transmitted 100Gbit/s between Texas and Florida.

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