Metro network design methodologies that build a next-generation network infrastructure based on this generation's services and demands

This paper describes two key network architecture design concepts that relate to evolving existing transport networks into economically viable next-generation optical networks. Today's metropolitan transport networks largely consist of synchronous optical network/synchronous digital hierarchy rings or switch-to-switch fiber connections for some form of optical Ethernet. The result is an optical-electrical-optical infrastructure that has limited use in providing wavelength services. Wavelength-division multiplexing (WDM) is the enabling technology for wavelength services, but it has limited penetration in the metropolitan area due to its cost justification being dependent primarily on fiber relief. The first part of this paper shows how existing services, primarily using time-division-multiplexing (TDM) transport, can be used to economically justify a WDM infrastructure while achieving significantly lower costs than legacy design techniques would produce. Dynamic bandwidth-on-demand (BoD) service is another elusive goal envisioned for next-generation metropolitan networks. This paper addresses how an economically viable BoD infrastructure can be built based on revenues from existing enterprise services rather than relying on revenues from new and unproven services. Quantitative analyses, presented in the paper, show the key parameters that determine when BoD services will be used, how bandwidth granularity affects BoD decisions, and how the customer's use of BoD drives service provider network design considerations.

I. Introduction

For some time, a common assumption has been that the role of optical networking is to support extraordinary growth of existing services and enable new large-bandwidth applications. However, for this vision to become a reality, it is necessary that both the envisioned new services are economically viable and there is an economically feasible path from the present networks to those that enable the new services. Metropolitan networks play a critical role in the overall expansion of network services. They not only provide for services within individual metropolitan areas, but they also serve as the gateways for wide-area national- and international-scale networks.