StrataCom first to bring low-cost ATM to market; New class of ATM service holds key to efficient transport of TCP IP traffic over ATM.

WASHINGTON--(BUSINESS WIRE)--Jan. 23, 1995--StrataCom Monday announced that it has become the first networking company to support a new class of Asynchronous Transfer Mode (ATM) service called Available Bit Rate service or ABR, that could dramatically lower the cost and improve the performance of using and providing high-speed wide area data communications services.

A new ATM service interface (ASI) board, available with Release 7.2 of the BPX, supports this new class of service making it the first ATM platform to support ABR (see technical note to editors). The ASI card includes ForeSight, StrataCom's rate-based, traffic management software and FairShare, StrataCom's patented per virtual circuit queuing and rate scheduler.

ABR: The Holy Grail for ATM

"Available Bit Rate services represent the holy grail for ATM users," said Joseph Baylock, vice president of networking technologies for Gartner Group. "ABR service will give carriers the ability to increase network utilization while opening the door to new ATM service pricing. This means that ABR services will be priced significantly less than other ATM classes of service such as continuous and variable bit rate services." Broad support for ABR is expected by both carriers and users.

"ABR is ideal for TCP/IP traffic," said Walter Gould, senior systems scientist for Computer Sciences Corp. "Because it relies on closed-loop congestion management mechanism, such as StrataCom's Foresight, ABR is the best class of ATM service to cost-effectively transmit TCP traffic over ATM without significant cell loss."

Commented Stan Kramer, director of public networking services at StrataCom, "From an end-user perspective, ABR services are the most significant development in the world of ATM standards. With this new class of service, users can finally receive truly cost-effective bandwidth-on-demand ATM services, while service providers can significantly increase the trunk utilization of their networks up to 95% by selling bandwidth that remains unused."

Rate-based traffic management is required to provide ABR services. The recent vote to implement a closed-loop, rate-based ATM congestion control standard by the ATM Forum has led to realignment of service classes to include ABR services. StrataCom introduced Foresight, the world's first rate-based, closed-loop congestion management system in 1992 and has implemented this system in its switches. With Release 7.2, this capability is now available for ATM connections on StrataCom's BPX switches.

Kramer noted that a result of the Forum's recent decision to move forward with a rate-based congestion management scheme has motivated many applications developers to begin work on premises equipment and applications that take advantage of new ABR services.

Carriers Voice Support

"We are excited at the prospect of providing ABR services," said Robert Decker, WilTel's director of ATM services. "This will give our customers the flexibility to select a service based on the demands of their applications and business needs."

Anticipating customer trials utilizing ABR services, Chuck Gibney, senior vice president at Cable & Wireless Inc., said, "We look forward to the possibility of being one of the first carriers to provide an ABR service over the StrataCom platform in our planned ATM trials with our customers. Cable & Wireless believes that available bit rate ATM services lend themselves much better to traditional LAN-to-LAN traffic than earlier ATM traffic standards that involve sophisticated traffic `contracts' with the customer and `policing' by the carrier.

"Because LAN workstations are allowed to transmit at any time, it is very difficult for LAN equipment to comply with a traffic contract. An ABR standard, and subsequent public services based on this standard, will allow ATM networks to carry LAN-to-LAN traffic much more efficiently with better performance for the end user. This is the whole idea behind ATM," Gibney concluded.

Because of its ability to allow users to leverage bandwidth in a dynamic fashion, ABR is best suited for bursty data applications such as bulk file transfers, electronic mail, and LAN-to-LAN connectivity.

StrataCom

StrataCom Inc. (NASDAQ:STRM), based in San Jose, Calif. develops, delivers and supports FastPacket networking systems for multiband ATM applications in private wide area networks and public carrier service offerings, such as Frame Relay and ATM.

StrataCom's family of products, including FastPAD, IPX, and BPX are used to integrate and transport a wide variety of corporate information, including voice, data, video, LAN's, image and multimedia traffic in narrowband to broadband ATM network applications. -0- Technical Note to Editors What is ABR?

ABR is a new class of ATM services that permits users to dynamically access available bandwidth not being used by other ATM services, such as continuous bit rate (CBR) and variable bit rate (VBR) services.

Unlike CBR and VBR, which require users to predict and declare application bandwidth requirements and service providers to reserve fixed amounts of bandwidth to meet quality of service requirements, ABR traffic is not "policed" (or tagged discard eligible). Instead, ABR is dependent on sophisticated traffic management mechanisms which monitor network traffic levels and detect the onset of congestion.

Network feedback is used to adapt ABR traffic flows to the available bandwidth in real time. This gives users the ability to reliably burst, for extended periods of time, with minimal cell loss and maximum useable throughput.

New Requirements for ATM Switches

With ABR services come new requirements that must be considered in evaluating equipment that can support this new class of service. These are: control, buffering and service policy.

Control

Flow control has a significant impact on the ability to effectively offer ABR services. The ATM Forum specifies a model, called Virtual Source/Virtual Destination (VS/VD), that segments the control loops of the network between the LAN and WAN, improving the performance of the connection and reducing the buffering requirements for the LAN device.

Other control methods, such as Explicit Forward Congestion Identification (EFCI) and Explicit Rate Marking, depend on end user systems to respond to and control congestion.

Buffering

To effectively offer new ABR services, ATM switches provide per-VC buffering allow "fairness" between users competing for available bandwidth. Wide area ATM switches must also provide large buffers, greater than 20,000 cells, to prevent cell loss during periods of congestion.

Service Policy

ABR services require minimum service levels to ensure fair class of service performance. Virtual circuit rate scheduling and guaranteed service queues are required for ABR services. StrataCom's patented FairShare per-VC queuing and rate scheduler guarantees minimum service levels to every connection and ensures fairness in allocating excess bandwidth.

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Note to Editors: IPX, FastPacket and StrataCom are registered trademarks and BPX, Foresight, FairShare, and FastPAD are trademarks of StrataCom Inc.

CONTACT: StrataCom

Barbara Burdick, 408/494-2003 or e-mail [e-mail]

David Callisch, 408/534-2521