OFC/NFOEC: Why Verizon Wants Terabit
That's because 400-Gbit/s Ethernet doesn't seem worth the potential trouble if 1 Tbit/s can be had. Glenn Wellbrock, Verizon's director of backbone network design, explained his reasoning during a panel at Monday's The Optical Society (OSA) , an adjunct conference to OFC/NFOEC.
"I just don't want to make so many changes in the network, because it's very painful," Wellbrock said. "Once we get a network in place, its really difficult to replace cards that haven't been depreciated, or even to move off that card."
His concerns come from bad experiences in 40-Gbit/s. The industry didn't declare any standards, leading to a variety of approaches that all came with high prices. And the first three years of 40-Gbit/s development were lost on a duo-binary modulation format that Wellbrock considered a dead end.
Verizon talks about 100 Gbit/s so much because "it's the easiest thing to do," he said. The industry has a standard approach that's going to be usable on 10-Gbit/s fiber spans. Verizon has one, possibly two, 100-Gbit/s spans running commercially, based on Nortel Networks Ltd. equipment. (See Verizon Switches On 100G in Europe and Rumor: Verizon's Got Another 100G.)
Standards bodies such as the Institute of Electrical and Electronics Engineers Inc. (IEEE) have yet to settle -- or even formally discuss -- what speed to shoot for after 100-Gbit/s Ethernet. So far, it look as if the carriers want to jump to Terabit Ethernet, while the equipment vendors are favoring 400 Gbit/s -- partly because the chips for a first generation of 400 Gbit/s would be available soon. (See Dare We Aim for Terabit Ethernet?)
Wellbrock said he'd be willing to use 400 Gbit/s if it turns out to be the best the industry can do. But he would like the industry to carefully deliberate whether 1-Tbit/s is doable, rather than go for the "safe bet" at 400-Gbit/s.
"We might be hurting ourselves by making an intermediate step when we don't have to," he said.
Wellbrock can afford to say that, because Verizon has a backup plan: It can always light more fiber for 100-Gbit/s links. Not every span has fiber available, so there might be some leasing involved. But it's something Wellbrock is prepared to do if he runs out of bandwidth before faster speeds are available.
Facebook doesn't have that option. Senior network engineer Donn Lee has been doing the conference circuit for several months, talking about Facebook's imminent need for 1-Tbit/s gear (and emphasizing how screwed Facebook feels about not having 100 Gbit/s available in 2007).
Lee was a speaker at the OSA Executive Forum and repeated his plea -- but with an added hint of resignation. Seeing that neither 400 Gbit/s nor 1 Tbit/s will arrive on his timetable, Lee is ready to build it himself.
"We are gonna have to go to 400-Gbit/s or 1-Tbit/s link aggregation bundles," said Lee. "Call it what you want; it won't be a standard because a standard won't be available. But link aggregation is in the future for us."
— Craig Matsumoto, West Coast Editor, Light Reading