IP-over-Sonet speeds Internet access

IP-over-Sonet speeds Internet access

paul palumbo

Transmitting Internet protocol (IP) data directly over high-speed Synchronous Optical Network (Sonet) fiber-optic networks could theoretically increase available bandwidth by 20%, produce cost savings by simplifying architecture complexity, and even eliminate some Asynchronous Transfer Mode (ATM) switching hardware.

To test this theory, engineers from IXC Communications, Austin, TX, and Ascend Communications, Alameda, CA, are moving forward with a 90-day technical trial in the Fort Worth, TX, area to demonstrate that IP data can be transferred directly over the Internet at OC-3 speeds of 155 Mbits/sec and higher.

Customers` voracious appetite for remote-access services and Internet connectivity has taken the industry by surprise, resulting in unmet demand for bandwidth. "When traffic bogs down on the Internet, it`s not necessarily due to insufficient bandwidth on the backbone but rather to router hand-off delays between networks," says Alan Smith, director of business development for IXC. "Data traffic has to run through a series of networks, and those interconnections are where the data gets held up," he explains.

Today, traffic over the Internet is connected directly from routers to DS-3 lines, which run to 45 Mbits/ sec. To run at 155-Mbit/sec speeds, data traffic would have to move up to OC-3 bandwidth levels. However, there are no routers that can directly handle an OC-3 connection. To get around that problem, network providers have to install an ATM switch to connect into a router at OC-3, and then take ATM traffic across the backbone to another ATM switch and back into a router again.

Ascend`s IP-over-Sonet solution eliminates the two ATM switches. At present, most Internet backbone networks run at DS-3 rates, except for MCI Communications` network, which operates at OC-3 speeds. MCI is upgrading to OC-12 at speeds of 622 Mbits/sec and higher with ATM switching in between.

"The conventional wisdom was that these IP networks would eventually migrate to ATM, but with voice separated from the data in many cases at the central office, companies are interested in ways to put IP directly over Sonet," says Bernie Schneider, vice president of strategic business development for Ascend Communications.

Schneider notes that Ascend`s Model GRF 400 Giga-Router supports both ATM and IP over Sonet. These GRF 400 systems are for T3 speeds and higher. In first quarter 1997, Ascend will deliver a device to put IP packets directly over OC-12 Sonet connections.

Breaking the OC barrier

Routers on the market today are at the limit of their processing speed at about 16 DS-3s. According to Smith, Ascend`s Giga-Router can handle multiple OC-3 and OC-12 traffic and switch at 16 Mbits/sec, which is not possible with today`s equipment. "If all works as planned, Ascend`s routers could increase both the backbone and routing speed of the Internet," he comments.

The purpose of the trial is to discover any problems and look forward to deployment on a national scale, according to both companies. IXC is already installing new fiber-optic lines across the country and has active fiber from Fort Worth to El Paso. IXC proposes to install routers in the Fort Worth point-of-presence site and run OC-3 electronics (supplied by Alcatel) to outfit a portion of the live fiber. Once the route is configured from Fort Worth, through Abilene, and out to El Paso, IXC will install the circuit and establish a loop back to Fort Worth. Ascend will then generate traffic to prove that the network can, in fact, switch at multiple OC-3 levels.

IXC is deploying Alcatel Sonet technology from Dallas, going West, which includes fluoride-fiber amplifiers that are OC-48 capable at speeds of 2.5 Gbits/sec. Amplifiers run in the 1500-nm range, but IXC stacks light signals through 16 windows for a total transport capacity of 38.4 Gbits/sec.

IXC`s traffic is 70% voice traffic, but that figure was 85% two years ago. "IXC is doing business today with a lot of Internet service providers that didn`t exist two years ago," Smith says, and observes that "data traffic is growing more rapidly than voice." q

Paul Palumbo writes from Seaside, CA.

(pull quotes)

"Companies are interested in ways to put IP directly over Sonet."

"Routers could increase both the backbone and routing speed of the Internet."