SONET still there, but playing quieter
Venerable optical technology handles new tasks for meshed optical networks
 
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While SONET will no longer be the only optical game in town, synchronous optical networking will be around for a long time as a core technology and as a protocol that is useful in framing other types of traffic that run over optical fiber, experts say.
Customers will buy Ethernet services or Gigabit Ethernet services, not SONET, but these Ethernet interfaces might very well be fronting a network that is based on SONET frames, they say.
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Some of SONET's continuing usefulness comes from its wide acceptance, says Chris Nicoll, vice president of market research firm Current Analysis. "It's well-defined and standards-based and helps new gear interoperate with the enormous existing SONET infrastructure," he says.
Even upstart optical companies that are redefining how fiber optic networks work value the SONET protocol. The technology can be used as a digital wrapper around other types of traffic such as Gigabit Ethernet, says Jeff Kiel, vice president and general manager at Sycamore Networks. This wrapper lets network managers flag errors and signal in-band among network devices, he says.
That doesn't mean SONET is ideal for these new networks. In fact, Standards Committee T-1, which writes SONET standards, is still tinkering with the technology. At its meeting next month, the group plans to focus on improving the transport of data over SONET networks, particularly Ethernet, according to Ken Biholar, vice chairman of the committee.
"Is SONET overkill? I think the answer is yes," says Thomas Nolle, president of CIMI Corp., a technology assessment firm. "Some service-level features are irrelevant."
That's because SONET as a way to transport traffic was designed to preserve dedicated circuits across optical networks. Packet traffic does not require such dedicated links, so the T-1 committee is developing ways to optimize transporting packet traffic using SONET.
In addition to its overabundance of features for packets, SONET is expensive and wastes bandwidth. SONET is designed to run on two separate fiber rings. If one ring fails, the other takes over. That means that at any given moment, half the network is being held in reserve.
Designers of new networks rely on meshed architectures rather than ring configurations to protect against failure. This frees the reserved bandwidth.
Some carriers are abandoning SONET except as a common interface to pass off traffic to another carrier. Yipes Communications is one such service provider that finds Gigabit Ethernet preferable because it is more flexible and faster to provision.
"Using SONET is like flying a jumbo jet from San Francisco to San Jose. SONET capabilities don't really add to what we need to do in the metropolitan [network] to deliver services," says Kamran Sistanizadeh, Yipes' chief technical officer.
Still, SONET will remain valuable in carrier backbones where high volumes of traffic must be moved from point to point with high reliability.
"We will use SONET for services if we need the reliability of SONET. If not, we will drive packets directly over wavelengths," says Robert Azzi, vice president of engineering for Sprint. "We will continue to grow our SONET rings. We will include it in metropolitan areas as we extend the core closer to customers."
Customers will likely not hear service providers touting SONET to them anymore. Nevertheless, it is still there supporting the services they buy. "SONET's not dead - it's been reincarnated," says Sycamore's Kiel.
RELATED LINKS
Surf the huge SONET resource Web site complete with glossary, FAQs and primers.
