Overlay networkOverlay network from a physical standpoint: that's complexityOverlay network, site layer: customers, partners, amplification, remote, point of presence Optical layer: Optical cross-connect, Optical fiber, Optical amplifiers, WDM SystemOverlay network Sonet layer: ADM and ring topologyOverlay network: IP connectivityOverlay networkOverlay networkOverlay networkFree SAS domestic networkInternet connectivity: an overviewxDSL Connectivity (en caption)xDSL Connectivity (fr caption) Internet Access layer Internet distribution and core