Softwarization of Mobile Network Functions towards Agile and Energy Efficient 5G Architectures: A Survey <s> Deployment and Nature of the EPC Control Logic. <s> Network architectures such as Software-Defined Networks (SDNs) move the control logic off packet processing devices and onto external controllers. These network architectures with decoupled control planes open many unanswered questions regarding reliability, scalability, and performance when compared to more traditional purely distributed systems. This paper opens the investigation by focusing on two specific questions: given a topology, how many controllers are needed, and where should they go? To answer these questions, we examine fundamental limits to control plane propagation latency on an upcoming Internet2 production deployment, then expand our scope to over 100 publicly available WAN topologies. As expected, the answers depend on the topology. More surprisingly, one controller location is often sufficient to meet existing reaction-time requirements (though certainly not fault tolerance requirements). <s> BIB001 </s> Softwarization of Mobile Network Functions towards Agile and Energy Efficient 5G Architectures: A Survey <s> Deployment and Nature of the EPC Control Logic. <s> Cellular core networks suffer from inflexible and expensive equipment, as well as from complex control-plane protocols. To address these challenges, we present SoftCell, a scalable architecture that supports fine-grained policies for mobile devices in cellular core networks, using commodity switches and servers. SoftCell enables operators to realize high-level service policies that direct traffic through sequences of middleboxes based on subscriber attributes and applications. To minimize the size of the forwarding tables, SoftCell aggregates traffic along multiple dimensions---the service policy, the base station, and the mobile device---at different switches in the network. Since most traffic originates from mobile devices, SoftCell performs fine-grained packet classification at the access switches, next to the base stations, where software switches can easily handle the state and bandwidth requirements. SoftCell guarantees that packets belonging to the same connection traverse the same sequence of middleboxes in both directions, even in the presence of mobility. We demonstrate that SoftCell improves the scalability and flexibility of cellular core networks by analyzing real LTE workloads, performing micro-benchmarks on our prototype controller as well as large-scale simulations. <s> BIB002 </s> Softwarization of Mobile Network Functions towards Agile and Energy Efficient 5G Architectures: A Survey <s> Deployment and Nature of the EPC Control Logic. <s> Software Defined Networking (SDN) and OpenFlow represent the most commonly deployed approaches of the so called Programmable Networks. SDN is an emerging network architecture, which performs the subdivision of control plane and data plane and allows greater speed, greater scalability, and greater ductility in terms of routing and forwarding. OpenFlow, instead, is an SDN component that characterizes the communication between a controller and the devices within the SDN network. Although SDN and OpenFlow work efficiently in wired networks, the integration of these new paradigms over the wireless networks represents still and open issue. In fact, in a dense wireless scenario with an high number of base stations and a limited radio spectrum is still difficult to manage in a proper way operations such as radio spectrum allocation, interference management, handover management, and load balancing among the cells. In this paper, we present a performance analysis of the SDN and OpenFlow over wireless networks. The aim is to evaluate potential advantages introduced by the SDN architecture in terms of Quality of Service (QoS) metrics such as throughput, packet loss, end-to-end delay, and packet delivery ratio. An exhaustive simulation campaign has been conducted through the OMNeT++ network simulator framework by taking into account the new generation IP-based broadband wireless networks. The obtained results shown that the SDN architecture with OpenFlow introduces benefits in the network in term of resource management, transmission data-rate and end-to-end delay. <s> BIB003 </s> Softwarization of Mobile Network Functions towards Agile and Energy Efficient 5G Architectures: A Survey <s> Deployment and Nature of the EPC Control Logic. <s> A network-assisted mobility management scheme has been proposed in this work for a Software-Defined Network (SDN). Instead of using just one controller as is the case in the legacy SDN, this work explores a distributed architecture with multiple sub-controllers. Detailed procedures for intra-domain and inter-domain handovers under this setting have been introduced and explained. <s> BIB004
The lack of a centralized controller for eNBs is discussed in BIB002 , and it is noted that the absence of such may result into an inefficient radio resource control. Virtualization has introduced the use of a centralized controller exploiting SDN in the EPC; however, this approach still lacks efficient power consumption management strategies, as it does not take into account daily traffic variations. Another management strategy that has to be investigated entails the use of a distributed approach BIB004 , where some decisions may be made locally (e.g., at the BSs) to configure instructions remotely within a centralized controller. For example, in the case where the MEC platform is colocated with the BS, it can collect traffic statistics, make local decisions (thus ensuring fast reaction to data traffic and mobility variations), and then share them with the central controller when required, for example, when a BS has to be deactivated. The traditional SDN architecture is centralized BIB003 , with the controller assuming the management responsibility for processing the entire network load. However, as the number of devices receiving network services increases, the processing load also increases. Thus, a centralized controller can potentially be a point of failure, despite its large computation and communication capacity. The placement of SDN controllers has been investigated in BIB001 , where authors provide an analysis about the determining factors that have to be taken into account. This analysis provides useful guidance for SDN operators and application designers, although there are currently no placement rules that apply to every network. Also, the EPC is aware of the aggregate traffic load per BS, but it does not have any knowledge about the energy side information (ESI) in the BSs (energy consumed, harvested, etc.). The lack of such information motivates the need for mobility and energy-aware procedures that can be deployed in the EPC, either in a centralized SDN controller or within subcontrollers (SC) as proposed in BIB004 . These shall perform mobility management tasks, while at the same time being aware of the available energy in the (energy harvesting) BSs. This will ease the energy management tasks in the BSs, by taking into account the current and forecast traffic load.