 used the existing telephone line to make an "internet call." This consumed costly circuit switched resources on the PSTN for an extended period of time. New technologies, such as DSL were then used to separate out Internet traffic from voice and carry it over packet networks. Movement then began to not only move data access away from circuit- switched networks, but also start carrying voice over packet networks. Technologies such as VoIP and softswitching were designed to essentially bring voice traffic onto the data network. The world of circuit switching, as we know it today will eventually migrate to a carrier-class packet/cell network. However, this will not happen overnight or in a flash-cut mode. The installed base of circuit switched gear is too huge and represents too significant an investment. Hence, softswitching architecture will co-exist with the existing architecture for the time being. The migration will start with services such as PRI offload, VoIP long distance, Class 4 replacement and, eventually, Class 5 replacement for the wireline world. This migration and evolution will bring on new challenges for the OSS. 1.3 IP Switching to the Core Before we describe the trend towards next-generation core networking, we must first define the core. There are two components of a network - the edge and core, which are engineered together to provide end-to-end services. The edge of a packet network is the point of attachment to customers. Edge devices typically perform traffic shaping, policing, protocol adaptation, prioritization, segmentation, fragmentation and re-assembly functions. Examples of edge devices are DSLAM, CMTS, Voice Gateway, Broadband Access Aggregator, and MPLS Edge Router. While the edge is charged with examining packets carefully, the core is focused on aggregating flows and switching traffic at high speeds. Examples of core devices are ATM switches, SONET nodes, DWDM switching and MPLS core routers. Multiple networking technologies, on multiple layers, are at play in the core. The initial