Enterprise Market Requirements

The enterprise market requirements include:

· Larger number of channels, each operating at lower speeds

· Transparency (since the spectrum of protocols used between sides is large, e.g., FDDI, ESCON, ETHERNET, DPT-SRP, IP, ATM)

· Monitoring and fault localization

· Survivability

· Low cost

The main drive for WDM links in the data communications environment has come so far from large financial institutions that wish to protect their valuable data by duplicating it at a geographically remote backup site. The need for wavelength routing networks in such applications is obvious if more than one primary and backup site exist in a large corporation.

The focus of such corporate networks is very different from that of long-haul carriers. While the latter are more interested in high aggregate capacity at one protocol (SDH), the former are more interested in having a larger number of channels, each operating at lower speeds (typically less than 1 Gb/s). Transparency is also a very important issue in this case, since the spectrum of protocols used between the sites is large (fiber distributed data interface, or FDDI, DPT-SRP, ESCON, fiber channel, ATM, and others). Monitoring and fault localization are central issues for the telcos, while enterprise networks typically have much less stringent requirements.

Another difference between these markets lies in fault tolerance. While SDH networks provide their own backup mechanisms, and thus do not need the optical layer below them to perform fault recovery (which can cause more havoc if not very carefully integrated), such fault tolerance is crucial in the data center backup case, where no such fault tolerance exists. Furthermore, since the telcos are heavily invested in legacy SDH equipment, it will be harder for them to integrate new optical layer fault tolerance into their systems.

In the long run, we expect wavelength routing networks in the data communications sector to provide a low-level, transparent, and configurable infrastructure for more specific technologies, mainly ATM and Transmission Control Protocol (TCP)/IP. Such a layered approach is not redundant, as the low-level optical layer and high-level electrical network play different roles. The main goal of the optical layer is to relieve high-layer nodes from the above-mentioned extra processing by providing high-capacity pipes of fixed bit rate that connect physically remote switching nodes. The goal of the electrical layer is to make efficient use of these pipes by statistically multiplexing lower-bandwidth bit streams with complex behavior (such as the ATM variable bit rate class) onto them. These two types of connections also operate on different time scales. While ATM virtual connections, or TCP IP connections, may have short life spans (from seconds down to milliseconds), lightpaths will typically operate on much longer time scales of hours or days, trying to adapt the network to changes in its usage pattern. Therefore, it is sufficient to have low-speed optical switching and configuration management.

Crucial factors in the penetration of optical technology into this sector are its

· cost

· technical maturity and

· future proof-ness.