©2021 IEEE. This paper is under review at IEEE Communications Surveys & Tutorials. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,1 creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. 5G Multi-access Edge Computing: Security, Dependability, and Performance Gianfranco Nencioni, Rosario G. Garroppo, and Ruxandra F. Olimid Abstract—The main innovation of the Fifth Generation (5G) smartphones have already been produced and sold by many of mobile networks is the ability to provide novel services with manufacturers. Currently, mMTC is not under deployment new and stricter requirements. One of the technologies that since many network operators have deployed LTE-M and NB- enable the new 5G services is the Multi-access Edge Computing (MEC). MEC is a system composed of multiple devices with IoT in relatively recent times. URRLC is a usage scenario that computing and storage capabilities that are deployed at the edge is more immature and challenging, and it is attracting a lot of of the network, i.e., close to the end users. MEC reduces latency attention from the research community [2]. and enables contextual information and real-time awareness One of the technologies that enable 5G to provide URLLC of the local environment. MEC also allows cloud offloading services is the Multi-Access Edge Computing (MEC). MEC and the reduction of traffic congestion. Performance is not the only requirement that the new 5G services have. New mission- consists in the deployment of storage and computing platforms critical applications also require high security and dependability. at the edge of the (radio) access network. In this way, MEC These three aspects (security, dependability, and performance) is enabling the delivery of services with low latency but can are rarely addressed together. This survey fills this gap and also enable context awareness and task offloading. Moreover, presents 5G MEC by addressing all these three aspects. First, we MEC is also the enabler of the edge intelligence, which is overview the background knowledge on MEC by referring to the current standardization efforts. Second, we individually present anticipated to be one of the main innovations of the Sixth each aspect by introducing the related taxonomy (important for Generation (6G) of mobile networks [3]. the not expert on the aspect), the state of the art, and the MEC is the name given by the European Telecommunica- challenges on 5G MEC. Finally, we discuss the challenges of tions Standards Institute (ETSI) that has an Industry Spec- jointly addressing the three aspects. ification Group (ISG) [4] that is standardizing MEC since Index Terms—5G, MEC, Security, Dependability, Performance. 2014. Before 2017, MEC was standing for "Mobile Edge Computing", but ETSI decided to generalize the standard to other access technologies, not only 4G and 5G, but also fixed- access networks and Wireless Local Area Networks (WLAN). I. INTRODUCTION ETSI MEC is not the only standardization effort on edge The Fifth Generation (5G) of mobile networks is currently computing. Fog computing and cloudlet are the two main under deployment. The main innovation is the provision of alternatives. The cloudlet was proposed in 2009 [5] and can wireless connectivity for various usage scenarios [1]: en- be considered the first effort on edge computing. The cloudlet hanced Mobile Broadband (eMBB), for services with very consists of a micro-cloud close to the mobile device. Fog high data rate requirements (up to 20Gb/s); massive Machine- computing has been firstly proposed by Cisco in 2011. Since Type Communication (mMTC), developed for connecting a 2015, fog computing is promoted and standardized by the huge number of Internet-of-Things (IoT) devices (up to one OpenFog consortium [6]. Fog computing has been introduced million devices/km2); Ultra-Reliable Low-Latency Communi- as an extension of the cloud computing paradigm from the cation (URLLC), for services requiring high reliability and core to the edge of the network. Fog Computing consists arXiv:2107.13374v1 [cs.NI] 28 Jul 2021 very low latency (up to 1ms). eMBB allows improving the of a three-layer architecture where clouds, fog nodes, and services provided by the Fourth Generation (4G) of mobile IoT devices interact. There is also another technology called networks. mMTC enhances the services that are now pro- Mobile Cloud Computing (MCC), but it is not edge computing vided by Low-Power Wide Area Networks, such as Long- since it consists of offloading of tasks from the mobile users Term Evolution MTC (LTE-M) and Narrowband IoT (NB- to the cloud. This paper uses as reference the ETSI MEC, but IoT). URLLC enables innovative advanced services, such as many considerations can also be generalized for the other edge mission-critical applications, industrial automation, and en- computing solutions, and, in our study, works on alternative hanced Vehicular to Everything (V2X) such as platooning or edge computing are also included. remote driving. eMBB services are under deployment, and 5G As already mentioned, URLLC is the most innovative and challenging usage scenario for 5G and the one that requires This work was supported by the Norwegian Research Council through the MEC. To support URLLC, MEC has to cope with high 5G-MODaNeI project (no. 308909). G. Nencioni is with the University of Stavanger, 4021 Stavanger, Norway requirements of ultra reliability, which means security and (e-mail: [email protected]). dependability, and of low latency, which is a performance R. G. Garroppo is with the Univrsity of Pisa, 56126 Pisa, Italy (e-mail: indicator. This is one of the reasons for which security, [email protected]). R. F. Olimid is with the University of Bucharest, 030018 Bucharest, dependability, and performance are three critical aspects of Romania (e-mail: [email protected]). MEC. 2 If MEC security has been to some extent investigated TABLE I during the recent years and several surveys are available, LIST OF ACRONYMS fewer surveys are available on performance and even less on 5G Fifth Generation of mobile networks dependability. To the best knowledge of the authors, this is the BSS Business Support System first work that jointly investigates the security, dependability, CN Core Network and performance of 5G MEC. CFS Customer-Facing Service DNS Domain-Name System This paper has the following contributions: EM Element Management • State of the art and challenges on the security, depend- ETSI European Telecommunications Standards Institute GR Group Report (ETSI) ability, and performance of 5G MEC. Each aspect is GS Group Specification (ETSI) addressed individually by using a similar structure and LCM Life-Cycle Management content organization. MANO Management and Orchestration MEAO MEC Application Orchestrator – First, the taxonomy of the investigated aspect is intro- MEC Multi-access Edge Computing duced. In this way, experts on the other aspects can MEH MEC Host MEO MEC Orchestrator better understand the investigated aspect. MEP MEC Platform – Second, the state of the art is presented. The state MEPM MEC Platform Manager of the art is divided into standardization efforts and MEPM-V MEC Platform Manager - NFV NFV Network Function Virtualization academic publications. NFVI NFV Infrastructure – Finally, the challenges are presented and organized NFVO NFV Orchestrator according to the ETSI MEC architecture. OSS Operation Support System RAN Radio Access Network • Challenges in jointly addressing security, dependability, SDN Software-Defined Networking and performance in 5G MEC. The joint provision of these SST Slice/Service Type three aspects and the related trade-offs are analyzed and VIM Virtualization/Virtualized Infrastructure Manager VM Virtual Machine discussed. VNF Virtualized Network Function The next section introduces the necessary background con- VNFM VNF Manager cepts and definitions of 5G MEC. Sections III, IV, and V present the state of the art and the challenges of 5G MEC re- lated to security, dependability, and performance, respectively. Section VI discusses the challenges and trade-offs of jointly addressing security, dependability, and performance aspects. Finally, Section VII presents the conclusions. II. BACKGROUND In the ETSI specifications [7], MEC is defined as "sys- tem which provides an IT service environment and cloud- computing capabilities at the edge of the access network which contains one or more type of access technology, and in close proximity to its users". Before presenting the state of the art of MEC focusing on the three different aspects, the fundamental concepts of MEC and the related enabling technologies are presented. Table I lists the main acronyms that will be used in the rest Fig. 1. ETSI MEC Reference Architecture [8] of the paper. Most of the MEC acronyms are defined in [7], [8]. Note that what is currently defined as MEC was previously defined as Mobile Edge. For example, MEO was the acronym Machines (VMs) and can offer and consume MEC services. of Mobile Edge Orchestrator. The MEP is a collection of functionalities required to run the MEC applications. The MEP can also host MEC services. More information on MEC applications can be found in [9] A. ETSI MEC Architecture (development) and in [10] (enablement). A MEC system is defined as a collection of MEC Hosts The MEC host-level management is composed of the MEC (MEHs) and MEC management necessary to run MEC applica- Platform Manager (MEPM) and the Virtualization Infrastruc- tions [7]. Figure 1 illustrates the ETSI MEC general reference ture Manager (VIM). The MEPM manages MEC applications’ architecture, divided into two levels: the MEC host level and life cycle, rules, and requirements (e.g., required resources, the MEC system level [8]. latency), and provides element management functions to the 1) MEC host level [8]: A MEH contains a virtualization MEP.