With the popularization of technologies such as IP and DWDM, the question looms as to whether SONET will eventually disappear. With a significant embedded base and its important restorative qualities, SONET clearly is not going away any time soon. But the role of this technology is certainly changing to meet the need of next-generation, packet-based networks.
For example, Riverstone Networks (www.riverstonenet.com) recently made available a 10-gigabit Ethernet router called the RS 38000 that combines the best of Ethernet and SONET using a new technology known as resilient packet ring (RPR).
Cisco Systems Inc. (www.cisco.com), Dynarc Inc. (www.dynarc.com), Lantern Communications Inc. (www.lanterncom.com), Luminous Networks Inc. (www.luminousnetworks.com) and Nortel Networks Corp. (www.nortelnetworks.com) in late January announced the formation of an alliance (www.rpralliance.org) to support the standardization and market adoption of RPR technology for metropolitan fiber networks. This new protocol will allow metropolitan area service providers to create high-speed, survivable ring networks optimized for IP and other packet data.
RPR is based on the IEEE 802.17 standard. It offers the 50-millisecond failover resiliency of SONET, but not SONET's heavy overhead or the extra, idle fiber connection required for redundant rings. RPR also offers the lightweight framing, easy manageability, and plug-and-play aspects of Ethernet, explains Andrew Feldman, vice president of corporate marketing and corporate development for Riverstone.
RPR also statistically multiplexes traffic for bandwidth gain. Today, one OC-192 can be divided in OC-48s because SONET is point-to-point. But RPR makes use of idle bandwidth on the fiber to enable a network operator to get more than 200 OC-48s off an OC-192.
"You need to get services not just on next-gen networks, but on existing networks," says Feldman. "If you want big customers, you've got to have SONET in your box. You get them to next-gen services by showing them a next-gen path."
However, the overhead of SONET is being put to good use, says Walter Moretto, product marketing manager for OPTera Connect at Nortel. "We need the SONET overhead for signaling and forward error correction [FEC]. It's not going to waste," he says. SONET overhead can be used for triple FEC to multiply the distances traffic can travel on a fiber link without adding new electronics, he explains. This results in significant savings today for long-haul applications and potentially later in metro applications.
Moretto adds that although SONET functionality and speed is increasing with such things as FEC and faster rates--10gbps today and 80gbps systems in development for both core and metro networks--he doesn't see SONET itself significantly changing. SONET traffic still makes up about 85 percent of the traffic on DWDM links, he says.
"SONET is not dead; what it's dead as is as a service delivery language," says Trey Farmer, executive vice president and COO for network facility wholesaler FiberNet Telecom Group Inc. (www.ftgx.com). "IP can't tell me if the laser is on or off or tuned." People tried to take SONET out of Layer 1 and use it for Layers 2 and 3, says Farmer. (For more on FiberNet, see "FiberNet Takes Fiber Resale in New Direction") "But SONET needs to be able to manage more nodes--it's a difficult system to expand. You want to take the qualities of SONET and strip it down and add stuff from IP," Farmer adds.
Despite the importance of SONET, some companies are coming out with new loop equipment that eliminates the technology completely.
One such example is a solution from Aura Networks Inc. (www.auranetinc.com). Aura's Radiance Optical Ethernet System is made up of several components. The R5000 Central Service Platform is a CO-based management platform that allows the carrier to collect network information and do bandwidth provisioning. The R1000 Premise Service Platform lets the service provider manage the link from the CO location without signaling network management protocol (SNMP); rather it uses Aura's proprietary Stealth IP technology. The company's Stealth IP technology can provide information about the network's optical power levels, voltages, AC and DC power supplies and fans, and can also dole out bandwidth in 1mbps increments--all without consuming user bandwidth. Also part of the Optical Ethernet system is the company's NetBeacon Element and Service Provisioning Management System.
The product, however, does not employ SONET technology in its first release because the company is initially targeting greenfield deployments from companies like Telseon (www.telseon.com) and Yipes Communications Inc. (www.yipes.com), says Alan Brind, senior vice president of marketing at Aura. But future releases may include SONET. Aura's only announced customer thus far is beta tester N2N Solutions Inc. (www.n2nsolutions.com), a building-centric LEC (BLEC) out of Schaumburg, Ill.
"SONET has a role because there's a huge infrastructure that's there," says Brind. "All this stuff is going to coexist together."
SONET is a good technology, but it was designed for TDM, he adds. "SONET is very, very cumbersome," he says. "It doesn't scale very well, and it's very slow to provision, and at OC-12 it kind of maxes out."
SONET as a protocol is taking on an important role as glue between the optics and IP layer both in metro and core applications, notes Karl Traberg, director of marketing requirements for Alcatel Inc.'s (www.alcatelusa.com) Terrestrial Networks division.
"Between optical cross-connects and large core routers, you will have SONET interfaces," he adds. "There's a lot of standardization going on to enable communications between the two."
SONET OC-192 is a $3 billion market in North America, and it's not going away, says Traberg.
"As we see the emergence of true optical ring functionality, SONET in the core will still be there for four- and two-fiber [applications]," he adds. "But once you see regional optical ring systems, SONET network elements will have less ring functionality and more of a traffic aggregation role because traffic is passed on to the optical layer. That's happening so provisioning is quicker. One hundred to 200 days to deploy an OC-48 circuit--of course that's not acceptable."
AT&T Corp. (www.att.com) and WorldCom Inc. (www.wcom.com) are planning 10 to 15 superPoPs in North America. These sites will be made up of optical cross-connects interconnected with DWDM, he says. Aggregation of small cities along the way will be handled by SONET add/drop multiplexers that have just a basic aggregation capability. "That's the path going forward," he says.
The big push in the metro market is for gigabit Ethernet and other new functions, Traberg says.
"ATM also is desired, but not to the same extent. The traditional SONET metro market at least for OC-48 is pretty flat, but OC-192 is growing," he says.
Alcatel's Optinex line includes the 1630 SMX multiservice metro SONET device, an OC-48/192 SONET system with traditional interfaces. The company expects to introduce a gigabit Ethernet interface to that product in the second quarter.
"The traditional interfaces are still the drivers. That just shows there's still a need for two classes of cross-connects--optical cross-connects in the core and SONET cross- connects in the access portion of the network," he says. "And Alcatel is strong in the cross- connect market, where we do both sides."
