ce whose price keeps dropping SO rapidly? Furthermore, for at least a decade, providers of packet-based networks have regularly overengineered their networks by placing more bandwidth into play than necessary. This stratagem let them Chapter 1 hide QoS issues from the user and keep customers as content as if they had utilized a private-line service.31 Some key new technology/specifications that are applicable to the metro access/metro core include the following: SONET/SDH and next-generation SONET/SDH Optical Transport Network (OTN) and Intelligent Optical Network (ION) IEEE 802.3z GbE IEEE 802.3ae 10 GbE IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) IEEE 802.17 RPR IEEE 802.EFM Optical Internetworking Forum (OIF) Optical User-Network Interface (O-UNI)³2 IETF GMPLS MAN evolution may include one or more of the following architectures and technologies: SONET/SDH Next-generation SONET/SDH IP over ATM over SONET IP over PPP over SONET DWDM (metro core) Wide WDM (WWDM), also known as coarse WDM (CWDM), for metro access Ethernet (Ethernet PHY in WAN) with VLAN and STP or RSTP Ethernet (10 GbE WAN PHY) All-optical networking (future) Figure 1-7 depicts one vendor's view of the possible evolution over the next few years. As a consequence of this panoply of architectural choices, carriers will have to decide between next-generation SONET, metro DWDM, CWDM, optical Ethernet/GbE VLAN, optical Ethernet/10 GbE WAN, and optical Advances and Opportunities in Next-Generation SONET Figure 1-7 IP + Optical A Cisco view of Ethernet Evolution the world. Source: Cisco Services Optimization promotional materials Next-Generation SONET Legacy SONET IP + Optical Integrated Control Plane Mesh Evolution Legacy SONET Metropolitan Network Migration Traditionally, the metro has largely been supported by legacy SONET and SDH transport, with a TDM-based infrastructue. This structure limits scalability, is built with single-purpose equipment, and its centralized multistep provisioning is costly. Today, we're in the middle of the next-generatio