e where this technology makes the most sense initially. A distinction needs to be made between an architecture that uses Eth- ernet at the edge (which has been deployed by carriers for over 10 years, typically using a point-to-point private line, traditional SONET, and/or ATM with distinct edge devices) and an architecture that uses Ethernet at the core (a new technology). In our definition, next-generation SONET mostly fits the former case, but it offers better streamlined data-ready/data- inclusive equipment with integrated Media Access Control (MAC) bridg- ing/MAC tunneling and/or IP routing, and improved operational efficiency compared to traditional SONET systems. Our definition, however, also includes the reverse case, where the NE is packet based at the core, but it has both Ethernet as well as traditional ITU SONET handoffs at the edge. In the first case, a packet path is emulated over a circuit path; in the latter case, a circuit path is emulated over a packet path. Table 4-1 depicts the various combinations of what we call next-generation SONET for the pur- pose of this investigation. As noted, there is no standard definition (that is, Next-Generation SONET and Optical Architectures Figure 4-2 Application example for next-generation SONET. App server App servers Next-gen Next-gen SONET SONET Engineering Manufacturing #1 Atlanta Boston Long Haul Backbone OC-192 Tape robotics Houston New York Next-gen Next-gen SONET SONET App server Manufacturing #1 Engineering App servers Manufacturing #2 Manufacturing #2 Corporate data centers All three Table 4-1 Edge (User Handoff) Core (Network Handoff) Various Topo- architectural SONET SONET Traditional SONET(a) Combinations Ethernet SONET SONET Packet (RPR) Next-generation SONET Ethernet SONET Hybrid: packet (RPR) on some Ethernet slots and TDM on other slots SONET Ethernet Ethernet based Ethernet Ethernet Ethernet (Discussed in Chapter 3, "Traditional SONET Architectures" (b)-Discussed in the companion book Chapter 4 published by a standards body) for "next generat