Service integration extends the life of SONET/SDH

Once viewed as too rigid to efficiently carry data traffic, SONET/SDH has received a much-needed makeover. Next-generation SONET/SDH now supports native Ethernet, storage-area networking protocols, and even WDM. With rumors of its imminent demise squelched—for the near-term, at least—next-generation SONET/SDH is quietly making inroads into territory formerly occupied by the so-called "God box."

Legacy add/drop-multiplexing equipment provides four basic functions: transmission, multiplexing, management capability, and the ability to add and drop traffic. Their next-generation equivalents, sometimes called multiservice provisioning platforms (MSPPs), can support multiple rings, interconnect and groom traffic across those multiple rings, and perhaps most important, feature a variety of interfaces. Native Ethernet and SAN interfaces like Fibre Channel, Escon, and Ficon can be terminated directly on the next-generation device.

"We're firmly convinced that SONET will remain an important, if not the most important, component of these next-generation ADMs [add/drop multiplexers] in the years ahead," asserts Robert Rosenberg, president of Insight Research (Boonton, NJ). "And we say this with the full realization of the growing importance of Ethernet," he adds.

Patrick Matthews, senior analyst with the Yankee Group (Boston), agrees that next-generation SONET/SDH will be the infrastructure of choice for at least the next three to five years. He sites three emerging technologies—generic framing procedure (GFP), virtual concatenation (VC), and link capacity adjustment scheme (LCAS)—as the fundamental building blocks for extending the life of SONET/SDH by enabling the transport of native Ethernet traffic.

GFP is a protocol-independent method for mapping a variety of data signals into standard SONET/SDH frames. It acts like a Cuisinart, says one industry insider, "chopping traffic of various sizes into small standard-sized packets that SONET understands." According to Matthews, GFP has been embraced by the industry because it provides a single defined mechanism for frame delineation and encapsulation, replacing the numerous proprietary techniques used before.

Employed to support much finer granularity for bandwidth efficiency, VC eliminates the standard rigid hierarchy of legacy SONET/SDH. "If you have 100 Mbits of Ethernet traffic," explains Matthews, "and you have to have use an STS-3 concatenated, you can now use virtual concatenation to 'right size' the pipe to an STS-1. You're basically providing 103 Mbits of bandwidth to carry that 100-Mbit signal so you don't waste bandwidth." VC is particularly attractive to carriers because it can be used within the legacy SONET/SDH environment as well.

Applied in conjunction with VC, LCAS enables the dynamic adjustment of the concatenated payload without service interruption. "It's the real meat behind virtual concatenation," asserts Kevin Wade, senior manager of product marketing at Turin Networks (Petaluma, CA). "[Virtual concatenation] makes it easier, but LCAS makes it dynamic. It removes all the barriers, all the negatives that people associate with SONET, namely that it's too rigid." Both VC and LCAS have been added to the Telcordia OSMINE process, which is "a real indicator of how much desire there is on the part of the carriers for these newer technologies," he notes.

The ability to provide wavelength services is becoming more prevalent as well; many vendors have added or are in the process of adding WDM capabilities, often achieved via a CWDM line card. However, DWDM costs are decreasing to the point where it is almost as economical to support DWDM as it is to support CWDM, asserts Scott Messenger, product marketing director in the Optical Group at Cisco Systems (San Jose, CA). He sites a growing trend among end users to leverage MSPPs for their WDM infrastructure. Today's MSPPs support true DWDM in a footprint four times smaller than legacy transmission systems. "Customers are looking to MSPPs not only for signal aggregation," he reports, "but also for the delivery of lambda-based services from any point to any point as well as optical add/drop multiplexing in the wavelength domain."

The next-generation SONET/SDH ADM market is poised to grow from roughly $900 million this year to about $9.5 billion by 2008, reports Insight's Rosenberg—nearly a 60% compound annual growth rate.

The $900 million carriers are projected to spend this year attests to their serious interest in the equipment. During SuperComm in June, BellSouth announced the selection of Lucent Technologies' Metropolis DMX and Cisco's ONS 15454 to upgrade its SONET infrastructure. A week earlier, Verizon announced the winner of its next-generation ADM request for proposal; the carrier selected Fujitsu's FLASHWAVE 4500. Fujitsu also won a contract from SBC back in April.

Independent communications operators are also taking note, choosing to deploy next-generation SONET boxes in greenfield applications rather than legacy equipment. While that remains a small percentage of the market, it nonetheless provides additional revenue streams for SONET vendors. Turin Networks, for example, recently added local telephone companies Grand River Mutual Telephone and Vermont Telephone to its roster of customers.

Thanks to increased service integration, next-generation SONET/SDH ADMs are starting to look a lot like the God boxes of a few years ago—but without all the hype. "The MSPPs are becoming God boxes," asserts Rich Goode, senior manager of strategy and business development at Lucent (Murray Hill, NJ), "but in an incremental fashion on a 'pay as you grow' path. I think the whole God-box market fell apart because it wasn't 'pay as you grow.' It was 'pay now,' and that just ended up being too much money."

More in Network Design