Hitachi`s high-octane SONET solution fuels nationwide network
Steve Smith
Bandwidth-friendly dense-wavelength-division-multiplexing (DWDM) technology may be key to Global Crossing Ltd.`s (Hamilton, Bermuda) North American Crossing fiber-optic network, but it is still counting on caffeinated Synchronous Optical Network (SONET) equipment from Hitachi Telecom USA Inc. (Norcross, GA) to provide a 10-gigabit-per-second fiber-optic pipe-line for carrying heavy traffic.
As part of a worldwide Internet- protocol-based fiber-optic network connecting five continents, the North American Crossing connects more than 120 metropolitan areas from Boston to Los Angeles, totaling nearly 20,000 miles of cable. Up until this year, the network featured multiple OC-48 (2.5-Gbit/sec) lines, but before the new millennium arrives, Global Crossing will have added multiple "network express lanes"--OC-192 (10-Gbit/sec) lines in high-traffic areas.
"The combination of OC-192, some OC-48, and others that may be composed of other traffic types--such as IP and ATM [Asynchronous Transfer Mode]--allows service providers to tailor quality of service to the type of traffic and the cost of the service to their customers," says Pete Westafer, Hitachi Telecom`s senior manager of marketing communications.
The North American Crossing includes a digital distribution infrastructure--a combination of nine geographically dispersed, domestic, and international media-distribution centers; specialized software that directs users to the fastest path to content; and a combination of private and public interconnects. The system handles more than 8.8 billion page views per month. "The North American Crossing network offers an ideal combination of virtually unlimited bandwidth and extreme reliability," says Russ Shipley, Global Crossing North America`s vice president of network services.
Keying the upgrade is Hitachi Telecom`s AMN 5192 SONET transport system, designed for both long-haul and metropolitan transmission. The 4-fiber bidirectional line-switched ring (BLSR) equipment supports 10-Gbit/sec rates via DWDM technology. Four-fiber BLSR is favored over 2-fiber BLSR because of its relative higher capacity and increased reliability offered by the larger number of fibers. The AMN 5192 provides protection against transport network outages caused by cut fiber or a failure at a node, automatically reversing traffic around the ring within milliseconds.
"SONET 4-fiber BLSR, with its 50-msec restoration standard, remains the best option for providing maximum network survivability," claims Westafer. "Other techniques such as optical rings and optical restoration in mesh networks offer promise. But large-scale application is still three to five years away."
As new SONET services emerge, the AMN 5192`s Flash eeprom software-based memory technology lets carriers like Global make in-service upgrades remotely and easily. The Flash-memory feature also reduces network recovery time following a power failure, compared to volatile RAM-based technologies that require tape downloads from a software storage device.
"Although the growth of SONET may be slowed by the introduction of other protection techniques," Westafer says, "it will remain a viable means of providing maximum network availability for many years to come."
