A comparison of SDN and NFV for re-designing the LTE Packet Core

With an increase in the number of mobile users and traffic, mobile network operators are finding it difficult to scale their radio and core networks. Further, hardware network appliances are expensive to procure and upgrade, and are difficult to adapt and program for new services. These trends have recently spurred several efforts to redesign various components of mobile networks, including the LTE Evolved Packet Core (EPC). Software Defined Networking (SDN) and Network Functions Virtualization (NFV) are two popular emerging networking paradigms that aim to increase network flexibility and scalability, while reducing the overall cost. With SDN, the control and data planes of the packet core can be separated, enabling cheaper packet gateways in the data plane, and an intelligent core network controller to handle the signaling and management functions. With NFV, the various hardware components that comprise the packet core can be virtualized and run as software on a cloud, enabling benefits such as elastic scaling and quick innovation. While several proposals exist to use SDN and NFV to redesign the EPC, there is no common framework to compare the new designs on various performance metrics. This paper presents the design and evaluation of two open-source implementations of the LTE EPC, one based on SDN principles and the other based on NFV, and presents a performance comparison of the two approaches. Experiments with our prototype show that an NFV-based implementation is better suited for networks with high signaling traffic, because handling the communication with the SDN controller quickly becomes the bottleneck at the switches in the SDN-based EPC. On the other hand, an SDN-based design of the EPC is better suited for networks with high data plane traffic, because SDN switches are often more optimized for packet forwarding than virtualized software appliances. We believe that our framework can be used to develop and compare several such design alternatives, and can serve as a guide for future redesigns of mobile data packet core networks.