A Virtual SDN-Enabled LTE EPC Architecture: A Case Study for S-/P-Gateways Functions

The recent initiative of Network Functions Virtualization (NFV) aims to deliver any data- plane processing or control-plane function in high volume data centers or network elements to decrease operational cost and increase deployment flexibility. In order to dynamically direct traffic flows between respective network elements, Software Defined Networking (SDN) can be seen as one enabler. In this paper, we focus on mobile core network nodes such as the MME, HSS, S- and P- Gateway as standardized for the LTE Evolved Packet Core (EPC). One straightforward solution for a virtualized EPC architecture would be to move all EPC network nodes completely into a data center and handle the data traffic via SDN-enabled switches. However, this solution would keep the conventional monolithic architecture unchanged. A possible split in the EPC functionality between a centralized data center and operator's transport network elements could be needed to provide the desired flexibility, performance and TCO reduction. Therefore, we have analyzed the EPC nodes and classified their functions according to their impact on data-plane and control-plane processing. We propose a mapping for these functions on four alternative deployment frameworks based on SDN and OpenFlow (OF). In addition, we investigate the current OF implementation's capability to realize basic core operations such as QoS, data classification, tunneling and charging. Our analysis shows that functions, which involve high data packet processing such as tunneling, have more potential to be kept on the data-plane network element, i.e. realized by an OpenFlow Switch. We argue for an enhanced OF network element NE+, which contains additional network functions next to the basic OpenFlow protocol.

I. Introduction

In today's operator networks the deployment of new network services comes at a high cost for integration and operation as network functions typically come with separate hardware entities. Network Functions Virtualization (NFV) [1] is a recent operator's initiative aiming at addressing this problem. NFV is transforming the way how operators architect their networks towards deploying network services onto virtualized industry standard servers, which can be located for example in data centers. In this way, NFV involves delivering network functions as software that can run as virtualized instances and that can be deployed at locations in the network as required, without the need to install hardware equipment for each new service. With this migration from hardware to software running in a cloud environment, NFV is expected to lower not only equipment cost (capex) but also operational cost (opex). Services are expected to be deployed more flexibly and can be scaled up and down quickly. From an architecture perspective, NFV can be seen as complementary to technologies such as Software Defined Networking (SDN) and cloud computing. Virtualized network functions might run in an operator's cloud environment and might be configured via OpenFlow. Whereas, these technology aspects are out of scope of the current NFV white paper [1], we address them by a thorough analysis of alternative architectures for functions deployment of an LTE EPC system in an operator cloud environment with SDN as a network enabler. Fig. 1: LTE EPC functional architecture