Smart grid technologies will equip the electrical grid of the future with two-way information flow between grid entities and consumers. This bidirectional information flow facilitates improved grid monitoring, control automation, energy efficiency, and sustainability. Several smart grid networking architectures have been proposed recently. However, the majority of these are restricted to subdomains such as home area networks or substation networks, or are not scalable. There is a need for an overarching and inclusive communication architecture which accounts for all smart grid communication scenarios. In this paper, we propose iCenS, a holistic smart grid networking architecture. We identify various communication scenarios, elaborate on the suitability of iCenS, and discuss how it can be used to solve smart grid networking challenges. We also present simulation results demonstrating the scalability of our design and its effectiveness in serving various types of smart grid traffic.