Many service providers are turning to Ethernet technology for MANs and WANs to support their new service offerings. And enterprise customers are asking providers to standardize on Ethernet as the user-to-network interface (UNI) everywhere on their networks to reduce expenses. Ethernet is familiar to enterprise customers and their IT staffs. It can scale to deliver bandwidth up to 10 Gbps to support demanding applications, and its bandwidth can be tailored to deliver performance that meets the needs of specific business applications.

Ethernet is also an extremely flexible offering for the service provider. Today's intelligent Ethernet equipment delivers advanced security and rich quality-of-service (QoS) capabilities, enabling providers to offer customized metro services. These offerings include a flexible mix of services and data rates for point-to-point as well as multipoint connections.

Ethernet can help enable service providers to reduce operating expenses, make more efficient capital expenditures, and introduce profitable, high-margin services. The cost of introducing new Ethernet services is relatively low, because the technology can be integrated and can interoperate with the service provider's existing transport infrastructure (running Ethernet over SONET/SDH, for example). In addition, Ethernet services can be a high bandwidth complement to a provider's existing service portfolio by integrating with existing frame relay and ATM services.

By offering Ethernet-based services that can support more advanced applications, service providers can differentiate their offerings from competitors, improve their profit margins, and improve their revenue potential over the long term. Building a Service-Driven Metro Network There are five important steps to consider when formulating a service-driven approach to building a metro network that meets customers' requirements:

• Service Definition - Specifies the various metro Ethernet services and their capabilities (the most important step).
• Service-level agreement (SLA) Definition - Specifies the attributes and performance that each service delivers.
• Architecture - Determines the objects within a network, their roles and relationships, and the network topology.
• Technology Deployment - Asks service providers to evaluate and choose specific technologies to support their metro services and architectures.
• Solution Deployment - Defines specific solutions and the products that will assume the different roles within the network.

A comprehensive, service-driven network employs multiple technology and product options to achieve the flexibility and scalability that is required. Many providers will opt for a hybrid of Layer 1, Layer 2, and Layer 3 technologies and products, rather than a single-layer solution. This hybrid approach can also be beneficial from a network management perspective if a single vendor can supply the underlying infrastructure.

Regardless of the underlying transport and access architectures, technologies, and products, Ethernet is the customer-facing interface to the service-provider's network or customer UNI. The network behind this UNI can be built using any technology. From a customer perspective, the services and their projected scale matter-not the supporting technology. After all of the planned services are determined, the service provider can consider architecture and technology decisions.