Ethernet at 30: The quiet before the storm

Ethernet celebrated its 30th birthday on 22 May. What started as a cable between copiers that ran a bit faster than today's home...

Ethernet celebrated its 30th birthday on 22 May. What started as a cable between copiers that ran a bit faster than today's home broadband services has evolved into the key technology in huge enterprise networks and even carrier data services.

For Ethernet trailblazers a recurring refrain is that Ethernet today is nothing like what they invented.

Bob Metcalfe, who as a researcher at the Xerox Palo Alto Research Center (PARC) wrote a memo describing Ethernet on 22 May 1973, recalled realising a few years later that the fledgling technology was outgrowing its origins at the lab in Palo Alto, California.

"I remember thinking in 1982, 'There are people buying Ethernet I have never met'," Metcalfe told an audience of networking pioneers and reporters at PARC last week.

From its first incarnation as a shared packet network that ran at about 3 megabits per second (mbps), Ethernet grew into a popular 10mbps technology. It gave each user their own dedicated bandwidth with switches, helped spawn IEEE 802.11 wireless Lans and eventually found its way into carrier data networks.

Along the way it supplanted a long list of rival technologies for networks, most notably Token Ring and Asynchronous Transfer Mode.

For that Metcalfe credits what he called the Ethernet business model: a formal standard with fierce competition among different implementations that nevertheless can work together, with continuing evolution of the standard that never leaves users of older versions stranded with useless equipment.

If some suppliers, service providers and research companies are right, Ethernet's acceleration isn't over yet. However, it may slow down to a less dizzying rate.

The industry's track record seems to call for a 100gbps speed within a few years.

"We've shifted the decimal point, on average, every four years," said Bob Grow, principal architect at Intel and chair of the Institute of Electrical and Electronics Engineers (IEEE) 802.3 working group, the body in charge of Ethernet standards. "If that's true, some time this year, we should be starting to shift the decimal point."

But the IT and telecommunications crash in 2001 has meant cutbacks in enterprise technology spending and a glut of data capacity on carrier networks. Now the talk is more of 40-Gigabit Ethernet and a wait of several years for broad use of it.

The current fastest Ethernet, at 10gbps, which was ratified as a standard last year, is more than enough for most carriers and enterprises so far, several analysts and executives said.

Gigabit Ethernet is the top speed in the backbones of most enterprise networks, where traffic from many servers and departments comes together, and on Ethernet data services from carriers to corporate customers.

"Right now, (10-Gigabit Ethernet) is coming onto the scene," said Bob Smith, senior director of emerging products and services at BellSouth, a major provider of Ethernet data services.

Though about 20% of the carrier's Ethernet customers are using Gigabit Ethernet services, "We have some customers up on gigabit speeds now that are wondering what to do with the other half of the bandwidth that they're not using," Smith said.

"Typically, it doesn't make sense to do the next speed until you have (widespread) adoption of the current speed," Grow said. For the length of time it has been available, 10-Gigabit Ethernet has had slower uptake than Gigabit Ethernet had at a similar point in the 1990s, he said.

For some potential users, including carriers, existing investments might hold back adoption of a faster technology for several years, according to Kevin Dillon, director of portfolio marketing at router supplier Juniper Networks.

Many have large investments in fibre infrastructure that will not work with anything faster than 10-Gigabit Ethernet. They would need to wait until that gear is fully depreciated, he said.

Whenever the next leap is taken, there are technical reasons to make the shorter step to 40gbps rather than develop 100-Gigabit Ethernet, analysts and executives said.

Ethernet interfaces at that speed would match up with traditional wide area network links at OC-768 (also about 40gbps), making it easier to design equipment and networks, said David Passmore, an analyst at Burton Group.

"Forty-gig in the wide area was all the rage two years back when everyone thought internet demand was growing exponentially," Passmore said. Although not much demand has materialised for such ports, chips developed for them could help to form the basis of 40-Gigabit Ethernet interfaces, he said.

At least one executive at Ethernet giant Cisco Systems believes 40-Gigabit Ethernet could be technically feasible within two years. Luca Cafiero, senior vice-president and general manager of switching, voice and storage, said the technical hurdles would be far less daunting for 40-Gigabit than for 100-Gigabit Ethernet.

In fact, Cisco Catalyst 6500 Series routing switches already can be equipped to support 40gbps per interface cards, and a card might be built with a single 40gbps interface, he said.

Other equipment suppliers are also lining up for this speed. Juniper Networks and high-speed Ethernet switch pioneer Extreme Networks say they can now support 40gbps of throughput on a line card.

However, at least one long-time Ethernet engineer doubts the industry will set a standard at 40gbps.

"Forty-gigabit will not be economically viable in terms of the effort the industry has to put in to develop a new technology," said Nan Chen, director of product marketing at equipment maker Atrica and a veteran of the Fast Ethernet standards process in the 1990s.

That speed could be achieved by simply bringing four 10-Gigabit Ethernet connections together using link aggregation, a much less expensive proposition than developing a new kind of interface.

If a whole new standard is to be developed, it should go all the way to 100gbps, he said.

Chen said he would not be surprised to see a formal call for interest in 100-Gigabit Ethernet at the IEEE in 2004, a standards development process of two years or so, and products in 2006.

"The economy may not be conducive for that kind of development, but if you look at the developments so far, that would make sense," he said.

There may be a way around having to create a new Ethernet interface that can handle 100gbps, he added. Ten 10-Gigabit Ethernet connections could be combined within a device using wave-division multiplexing, going out through an optical 100gbps interface. The current 10-Gigabit Ethernet standard includes an option for doing this using four 2.5gbps links, he said.

Other experts say 40gbps could be worth the work.

In the past, Ethernet has been used mainly in Lans inside an organisation's own building. Aggregating four fast links was relatively inexpensive in that setting, so there was no need to change gears until 10 times the speed was needed, Passmore said.

Now fat Ethernet pipes are also used over long distances, where networks typically are more expensive to roll out and connection speeds have gone up roughly by multiples of four, most recently from OC-48 (2.5gbps) to OC-192 (10gbps) to OC-768 (40gbps). 

"In the Wan, going by 4x is perfectly adequate," Passmore said.

Formal work on an Ethernet standard faster than 10gbps has not even started, according to Grow. No one has yet submitted a call for interest for a new Ethernet at either 40gbps or 100gbps. But that may just be the quiet before the storm.

"There would be significant disagreement on what is the correct next speed within the committee," Grow said. Once a standards process begins, it typically takes three years to finish, he said.

Actual demand for the technology is another question. Some observers do not see a faster Ethernet in wide use until 2010 or so.

"We still have a long way to go before we are through aggregating Gigabit (Ethernet) up to 10-Gigabit," said Dave Dunphy, an analyst at Current Analysis.

Even BellSouth's Smith, who is optimistic about the eventual need for more speed, is taking the long view.

"Ten years out, 40-Gigabit will be deployed as commonly as 1-Gigabit is today," he said.

Juniper's Dillon hinted at a glimmer of demand for a faster Ethernet. Some of the company's carrier customers are already aggregating multiple 10-Gigabit Ethernet links between their facilities at the edge of metropolitan networks, he said.

The early market for a faster Ethernet might be limited to the cores of campus networks, links between campuses and the edges of carrier networks.

As for faster Ethernet pipes to servers, I/O technology is only beginning to catch up with 10-Gigabit Ethernet.

"Forty gigabits or 100 gigabits would be completely wasted on a server," Passmore said.

However, one Ethernet pioneer is looking to overcome this barrier.

Judy Estrin, chief executive officer of Packet Design, spun off a new company in March to develop a scalable I/O architecture. With the new company, Precision I/O, Estrin hopes to break through current scalability limitations to make server I/O scale up to handle 40gbps or more, she said at the Ethernet anniversary event last week.

Estrin, who has founded and sold several successful networking companies since the 1980s, has a special attachment to Ethernet.

She was introduced to the technology in its early days at a seminar given by Metcalfe at PARC. Estrin attended the seminar with fellow students after they went out to lunch for her 21st birthday and she enjoyed her first drink. That may have been one reason it made such an impression on her, she said.

Stephen Lawson writes for IDG news service

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