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SLAs safeguard the optical option.

Optical and other applications require service foundation customization.

Tremendous excitement surrounds optical technology because of its promise to make bandwidth scarcity a relic of the past. How does bandwidth abundance at the optical layer, however, translate into services that enterprises can depend on for applications, such as high-speed intranets, delay-sensitive extranets, off-site backups and Internet access?

The key is understanding how to recognize that optical networks are evolving into two layers--the optical-transport layer and the optical-service layer. The optical-transport layer is composed of optical-transport switches (OTX) that use dense wavelength division multiplexing (DWDM) technology to create abundant raw bandwidth.

The optical-service layer is responsible for refining raw bandwidth into data services. The equipment in the optical-service layer is a new class of device called an optical-service switch (OSX), which has interfaces that match the speed of optical net works (such as OC-48 and OC-192), and has the quality of service (QoS), metering and measurement capabilities needed to enable the creation of service-level agreements (SLAs) for each of the applications listed above. OSXs combine the native Internet protocol (IP) support of IP routers, the QoS associated with asynchronous transfer mode, and extend the simple, but well-understood, SLA definitions of frame relay.

Consider a Hollywood special-effects company that requires secure, high-bandwidth connectivity to its business partners. The company's needs are dramatically different from those of an insurance company that generally needs lower bandwidth for its intranet, but requires high bandwidth to support absolutely reliable off-site backups.

How does a service provider resolve the conflicting demands of each SLA requirement, while maintaining a unified network and operations process? The solution is to create a small set of basic service-foundation classes and then customize them along several dimensions to meet the needs of each particular application, such as intranets, off-site backups and extranets.

The virtual private line (VPL) foundation class is defined to provide behavior equivalent to that of a private line, namely zero packet loss with minimal latency and jitter. Like a private line, this service is ideal for off-site backups. Unlike a true private line, however, which is only available in discrete bandwidth chunks, a VPL can be sized by using the metering dimension to meet the specific needs of the specific application (such as 1 Gbps to match the rates of Fibre Channel interfaces on storage equipment). It can be further tuned for an off-site backup application by using the time dimension, giving the VPL high bandwidth at night (when backups are made) and low bandwidth during the day. Finally, a diverse path requirement can be made to ensure high availability, and reporting can be enabled to verify that the delivered performance was indeed without packet loss and had minimal delay.

The flexible data line foundation class is defined to provide behavior equivalent to that of a frame relay virtual circuit, before service dimensions are applied. To make this foundation class appropriate in the insurance company intranet example, first add classification to give time-sensitive applications, such as voice and SNA, higher priority than normal traffic. Metering is then applied to limit the rate of high-priority traffic, while providing ample bandwidth for normal traffic. Finally, a dedicated backup path with 50 ms fail-over is provisioned for high availability.

The broadband virtual private network (VPN) foundation class creates a closed user group that enables secure communications between the special-effects company example and its business partners. The service dimension of metering provides high-bandwidth service (e.g., 200 Mbps), which is sent over the real-time class to ensure rapid data transfer. The reporting for this application shows the data sent from/to each member of the VPN, any data losses and the resulting delays.

With minor changes, the concepts described here can be extended to support other types of applications, such as usage-based billing for an MP3 music distribution company, or pay-per-view video. These SLAs are close to reality today, and when made available, will unleash a new set of business models for commerce over optical networks.

Kavi is director of product management for Tenor Networks in Acton, MA. Circle 261 for more information from Tenor Networks
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Title Annotation:Industry Trend or Event
Comment:Those adopting optical networking technology to increase bandwidth need to carefully establish a service foundation and work out highly customized service level agreements (SLA) to take full advantage of the reliability and scalability of optical systems.
Author:Kavi, Prabhu
Publication:Communications News
Geographic Code:1USA
Date:Nov 1, 2000
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