itan fiber architectures with the stated goal of being able to handle data more efficiently than traditional SONET and to bring down the cost for service providers and companies. If successful, the groups will have a standard by 2003 that will define how the dual-ring architecture of SONET can be used without leaving one ring idle as backup the way SONET does. This new technology is known as Resilient Packet Ring (RPR). It takes advantage of the fact that data flows are less time dependent than voice. According to observers, these standards will let companies and service providers deploy metropolitan area optical band- width SO that it can be distributed efficiently for IP, with a focus on Ethernet. At the same time, there are major advances in SONET. These evolving systems are being called next-generation SONET. Vendors are now begin- ning to support the ITU X.86 and American National Standards Institute (ANSI) T1X1.5 Generic Framing Procedure (GFP) standard for direct Eth- ernet over SONET (EoS) services. This technology enables new products for LAN-to-LAN connections with fewer network elements. 29 Single-chip EoS mappers enable direct LAN-to-LAN communication over existing SONET/ SDH networks and are planned to be used in Ethernet switches, stand- alone data service unit/channel service unit (DSU/CSU) systems, and Advances and Opportunities in Next-Generation SONET SONET add/drop multiplexers (ADMs) within the LAN and metropolitan access (edge) network. EoS maps Ethernet frames into SONET/SDH pay- load and, as such, effectively transforms a portion of the SONET network into an invisible tunnel between LANs to provide TLS. There is also interest in Generalized MPLS (GMPLS) because it extends the MPLS control plane to encompass time division (SONET ADMs), wave- length (optical lambdas), and spatial switching (incoming port or fiber to outgoing port or fiber). The extension of LAN capabilities to the metro area has also been called the optical Ethernet. Efforts of the IEEE 802.EFM, such as Ethernet in the First 