A glass act

Dense wave division multiplexing is elbowing its way into the metro environment, and the push to run Internet protocol and asynchronous transfer mode directly on the optical layer is gaining momentum. Cost is a key factor as carriers gear up for data traffic on their networks. Although vendors, no doubt echoing carrier customer sentiments, don't want to eliminate Sonet from the game, they are devising methods of adding intelligence to lightwaves, which will further fuel IP and ATM over glass.

"We'll see a decline in Sonet in the future and a dramatic increase in DWDM with ATM and IP," said Erica Henkel, an industry analyst with Frost & Sullivan.

The attraction is that there is no electronic layer and no electronic conversion. Wavelengths are protocol-independent, and cutting out conversion makes for cleaner throughput and better performance. Osicom Technologies is already seeing a shift toward data protocols.

"We have seen an incredibly large amount of movement in that area," said Ron Mackey, executive vice president of technology at Osicom. His company is supplying product to a Chinese cable company building a 100% IP network and an unnamed U.S.-based competitive local exchange carrier building an ATM-based network that will mirror that of an incumbent.

The key drivers are cost and network simplification. New WDM products incorporate monitoring and protection at the optical layer. Although Mackey acknowledges that the level of protection might not meet the five nines (99.999%) telecom reliability goal, the difference is negligible.

"Deploying a network based on Sonet can cost 50% more than what the current [IP] architecture calls for," Mackey said. "Sonet is key in providing fast recovery and detection of network errors. If you can do 99% of what Sonet can for half the price, that's a compelling argument." But Mackey is cautious about creating totally non-Sonet networks, noting that Sonet was designed and is ideal for voice traffic.

IP and ATM likely will be deployed first in the metro environment on the optical layer, but other protocols are supported, too. For example, a "mindboggling" number of networks are based on some form of Ethernet, so metro DWDM systems are also including gigabit and fast Ethernet interfaces, explained Don Smith, vice president and general manager of OPTera solutions at Nortel Networks. "A benefit of data transport is the flattening of that network," he said. It also affords new service opportunities, such as creating virtual campus networks.

Letting IP and ATM handle data is optimal, but only if network management can keep up. Carriers desire a single-view network management system, which is being realized in wavelength management technologies. Lucent Technologies recently announced WaveWrapper, and Nortel Networks has an alternative solution.

"Our approach is to provide an optical service channel from where you enter the system to where you exit the system," Smith said. "It behaves in-band but acts out-of-band."

The service channel travels on the wavelength in addition to, but independent of, the payload. Because it is optical, it can pass through other devices on the system, including optical add/drop multiplexers or optical cross-connects.

Management will drive acceptance of wavelengths and IP or ATM over optics. But the IP/ATM over optics movement is strong enough to capture budget bucks from carriers.

Henkel predicts that in 1999, all U.S. carriers will spend 25% of their new network investment monies on packet-switching technologies. By 2000, that will increase to 40%. And in both years, "carriers will invest another 25% into software for network monitoring, service activation, billing of these new services, and for integration with the existing legacy equipment," she said.

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