To handle the enormous demand for data services, the metro network must be able to respond quickly and dynamically to the networking services required by end customers, as opposed to simply providing fixed point-to-point connectivity. The environment has shifted in favor of systems that can support many diverse services with the rapid deployment of a flexible, intelligent optical infrastructure. There are four key operational requirements for success in the metro networking equipment: transparency, flexibility, simplicity, and intelligence.

Transparency

A key requirement in the metro network is the ability to connect all of the various services offered in today's metro network (as well as those that may be offered in the future) in a bit-rate– and protocol-independent manner over a shared optical infrastructure.

The Internet has proven the value of transparency from an application viewpoint. The success of the Internet as a global communications medium is due, in no small part, to the fact that it is transparent to the traffic carried within the IP frames. This one attribute has allowed Internet applications to evolve from e-mail, file transfer protocol (FTP), Telnet, and Gopher to support hypertext markup language (HTML) browsing, shared computing, streaming media, and a host of other services today, with more to come in the future.

In contrast, the Internet faces significant challenges in supporting real-time-oriented services, such as voice and SAN, which demand strict quality of service (QoS) tolerances that are difficult to achieve on a best-effort connectionless network such as the Internet. The metro is the place where there is demand for the widest range of services. Here, SONET/SDH for voice services and Fibre Channel or enterprise system connection (ESCON) for SANs are the preferred Layer-1 transports.

Flexibility

Flexibility means supporting a wide range of network topologies, such as point-to-point, rings and mesh configurations. This flexibility works in tandem with transparency to allow for native support of metro traffic. Different application services require different connectivity models. IP and Gigabit Ethernet traffic is best served by a mesh network environment, whereas SANs are typically best served in point-to-point configurations and voice traffic by using native SONET/SDH rings. Deploying just one specific topology either limits the service provider to supporting only a limited set of services or, more often, forces them to incur extra cost and complexity in adapting traffic from one topology to another.

Simplicity

Simplicity refers to the ability to rapidly roll out new services over the metro optical network in a straightforward and effective manner. The complexity of the supported services must not be amplified by the metro infrastructure used to connect them. By combining the functions of wavelength transmission and switching into a single element, the OADX simplifies the design of the optical transport network. Integrating WDM transport with the ability to switch any input wavelength to any output wavelength makes it possible to configure and reconfigure wavelengths in support of services without truck rolls, simplifying the initial infrastructure's ability to accommodate future services.

Intelligence

Intelligence entails the ability to discover and adapt the current network topology and conditions to support optical lightpath set-up, protection, and restoration on demand. The different services offered in the metro network require different path characteristics in terms of wavelength topology and protection. By supporting an intelligent control plane, the optical wavelength network can provide the appropriate optical transport infrastructure for the application.