Ethernet-over-copper for all
- By William Jackson
- Jun 05, 2006
CHICAGO'Copper is so 20th century. But for many organizations not served by fiber-optic cable, copper still is the only practical network connection and an industry is growing up to supply Ethernet service over the existing copper infrastructure.
'Fiber is the ultimate medium for broadband,' said Gary Bolton, VP of product management for Hatteras Networks Inc. of Research Triangle Park, N.C. But, 'the growth of fiber is not great.'
That is because it often is economically practical to provide fiber only for customers willing to pay for lots of bandwidth. Penetration of fiber has grown only from 9 percent of business locations five years ago to 11 percent today, Bolton said, although major metro areas such as New York and Washington have higher concentrations.
'Fiber is great if you can get it,' said Craig Easley, associate vice president of marketing for Actelis Networks Inc. of Freemont, Calif. 'Otherwise, there is copper there.'
Hatteras and Actelis are two companies demonstrating Ethernet-over-copper products this week at the GlobalComm trade show. Using switches, repeaters and customer premises terminators built to the IEEE 802.3ah standard for Ethernet in the First Mile, carriers can extend their Metro Ethernet networks past their fiber footprints and replace traditional T1 connections with faster, cheaper native Ethernet at speeds ranging between 2 to more than 50 Mbps.
The Institute of Electrical and Electronics Engineers ratified 802.3ah in 2004, and the first standards-based systems were deployed that year.
'The market is just emerging,' Bolton said. 'Last year was an early adopters year. This year it is starting to explode.'
Although First Mile Ethernet primarily is a carrier technology, government, military and educational installations offer the next-largest slice of the market. Although principal sites and headquarters often are served by fiber, outlying offices, campuses and military bases often still rely on copper infrastructure. Easley said a U.S. Army base in Baghdad is using its ML100 EFMplus switches to extend Ethernet connections over a copper loop between sites.
Bolton said Ethernet over copper is not competing with traditional Ethernet, but is extending the reach of those services.
'We are not selling against fiber,' he said. 'It's a huge market.'
The market is huge because traditional phone carriers have been installing copper infrastructure for decades. But that longevity also creates problems and means that Ethernet signals can take a lot of grooming to get adequate speeds and distances over copper.
'That copper plant is a fickle beast,' Easley said. 'It's been spliced and tapped and bridged over the years. It's difficult to run a high-speed service through an unpredictable medium and get reliable results.'
There now are two flavors of First Mile Ethernet, the higher-speed, shorter-range 10PASS-TS and the lower-speed, longer-range 2BASE-TL. Both Hatteras and Actelis are offering 2BASE-TL products. Because 2BASE-TL operates in a baseband, it cannot run on lines also providing plain-old-telephone service at the same time. But it can provide all of the services that Ethernet provides, including voice over IP.
The nominal speed of 2BASE-TL Ethernet over a single copper pair is 5.7 Mbps, but the real-world maximum is more likely to be 3.5 or 4 Mbps. Multiple pairs can be bonded to provide higher rates. He said carriers using Hatteras equipment use an average of 2.3 pairs to deliver service to their customers, although the company is demonstrating a 40-pair bundle at GlobalComm that delivers 225 Mbps. In reality, a seven- or eight-pair bundle probably is the practical upper limit for copper, Bolton said.
'In practice, when you get above 20 Mbps the economics are there to pull fiber,' he said.
The company is targeting the mid-band Ethernet range of 2 to 20 Mbps as the sweet spot for its customers. By allowing carriers to extend this level of Ethernet services to customers not served by fiber, they can generate revenue and help create demand for higher-speed Ethernet that will make installation of fiber economical.
'What we are doing is enabling fiber to be deployed more rapidly,' he said. He is confident the market for Ethernet over existing copper is large enough that Hatteras does not have to worry about putting itself out of business any time soon.
The company's product suite includes the HN 4000 layer 2 switch for the carrier, which can handle up to 40 pairs of copper, and the HN 400 that resides at the customer premises to terminate connections.
Bundling copper pairs raises problems of its own. Crosstalk or interference between pairs can result in wide fluctuations in performance, lowering the overall available bandwidth and range. The Actelis EFMplus switches use signal processing to groom the performance of each copper pair to get the best overall performance out of a bundle.
Although the peak performance of a single pair in an ungroomed bundle might be as high as 4 Mbps compared to 3.8 Mbps in a groomed bundle, the company claims a nearly two-fold increase in overall performance by bringing the speed of all of the pairs to a more consistent level.
The maximum range for 2BASE-TL First Mile Ethernet is 9,000 to 12,000 feet, but Actelis is announcing this week the first EFM repeater, the XR239. This is a passive device that serves two copper pairs and receives its power from the switch. One switch can power up to four repeaters, so up to eight repeaters can be used if they are being powered by switches at each end.
'You can only send so much energy down the phone line' before it interferes with the signals, Easley said.
William Jackson is a Maryland-based freelance writer.