IP/MPLS SONET/SDH SONET/SDH ETHERNET Intelligent Optical Net TRADITIONAL OVERLAY INTELLIGENT, IP-BASED TRANSPORT NETWORKS OPTICAL NETWORKS are offered by the ION; (b) the carriers may not want to relinquish provisioning control to users and switched virtual connections if either Frame Relay or ATM have not taken off; (c) the national network is not a simple cloud of a few nodes under the administrative domain of a single carrier as often implied by vendor presentations; and (d) only around 20,000 of the 4,600,000 commercial buildings in the United States currently have fiber, making the promise of instantaneous provisionability a mere chimera. Table 1-2 maps some typical customer services to possible underlying technologies. It turns out that a multifaceted carrier will need more than a single technology and/or a single architecture. Table 1-3 lists the available metro access/metro core technologies and the advantages and disadvan- tages of each technology. The following lists the metro optical network technology from an approach and supportive technologies standpoint. The key optical metro access/metro core approaches include Ethernet at the core ELECs Next-generation SONET Next-generation communications carriers DWDM/GMPLS All optical Chapter 1 Table 1-2 CWDM/DWDM TDM/SONET VLAN/GbE Best-Fit Mapping Between Services and Technologies Private line Optical lambda Channel extension Multimedia Table 1-3 Available Metro Technology Strengths Weaknesses Cost Effective Access/Metro Core Technologies SONET Standardized, proven Inefficient for mixed DS1, DS3, OC-3 LL; protection, and traffic and service DS1, DS3 ATM; and performance interface DS1 Frame Relay monitoring granularity Hybrid Standardized, proven Additional elements Frame Relay; ATM/SONET protection, and may be required, DS3, OC-3 ATM; performance may increase monitoring network complexity, transparent LAN and have high costs Multiservice Highly scalable and Still relatively OC-x LL; supports multiple expensive, often OC-x ATM; protocols limited to optical and