The document discusses key concepts related to Next Generation Networks (NGN). It describes the NGN reference architecture which includes a transfer network to carry information flows, a network control for establishing links, and service control related to the final service provided to users. It also discusses NGN services, quality of service parameters, mobility, nomadism, presence management, resource control, identification and authentication, metering and monitoring, and security issues in NGN. Finally, it provides examples of NGN soft switch architecture and BSNL's migration strategy to NGN.