Service convergence, content digitization, rapid and flexible service delivery, reduction of capital and operating costs, economies of scale, changes in telecom policy and regulation and ever increasing competition have been key factors in the evolution of virtualized Next Generation Networks (vNGNs). IP-centric converged networks aim to provide a multitude of services over a single network infrastructure. Tremendous success and benefit of server virtualization in data centers is driving the adaption of network virtualization. Network virtualization is applicable to enterprise data center and enterprise as well as wide area networks. This paper is network virtualization aspects of service providers’ next generation network.