, it would be preferable for the carrier's network to accept this handoff and then convert it, if nec- essary, to a SONET/WDM format. Because Ethernet interfaces are very cost effective for the end user compared to traditional WAN interfaces, TLS- based services (supported by Ethernet-ready edge NEs) would be an attrac- tive offer to corporations. It also saves costs for the network provider by eliminating the adaptation functions to ATM. Although ATM can support speeds of tens of megabits per second, it does not support interfaces oper- ating at 1 or 10 Gbps equally well. Native data interfaces for other protocols on edge NEs, such as ESCON or FICON, would provide similar values depending on user-specific requirements. At the end of the day, however, native data interfaces are not necessarily intrinsic to WDM only. As noted, next-generation SONET aims at support- ing these same interfaces. Hence, the choice between WDM and next- generation SONET is really a traffic-engineering consideration once we get past the initial cost. This raises the following question: How much growth can be anticipated in a metro access subnetwork? By deploying a WDM-based photonic network, the service provider gains an access or interoffice transport infrastructure that is flexible and scal- able. However, planners need to ascertain that what could turn out to be a high NE cost does not become multiplicative and all 8, 16, or 32 buildings on the ring are each forced to incur a high nodal cost. Although a long-haul network may be a two-point link, or at most be a ring/mesh with a half a dozen or SO high-capacity points (say, in several states), metro access rings typically have a larger number of nodes on them, unless a nonredundant building access is utilized, as shown in Figures 1-8 through 1-12 in Chap- ter 1. A 16-building access ring using next-generation SONET with a Dense Wavelength Division Multiplexing (DWDM) Systems $30,000 device would cost the provider $480,000 in nodal equipment; a ring using DWDM with a $60,000 device woul