Policy-Based Network Slicing Management for Future

Policy-Based Network Slicing Management for Future Mobile Communications Alberto Huertas Celdrán∗ , Manuel Gil Pérez∗ , Félix J. Garc´ıa Clemente† , Fabrizio Ippoliti ‡ , and Gregorio Mart´ınez Pérez∗ ∗

Departamento de Ingenier´ıa de la Información y las Comunicaciones, University of Murcia, 30100 Murcia, Spain Email: [email protected], [email protected], [email protected] † Departamento de Ingenier´ıa y Tecnolog´ıa de Computadores, University of Murcia, 30100 Murcia, Spain Email: [email protected] ‡ Computer Science Division, School of Science and Technology, University of Camerino, 62032 Camerino, Italy Email: [email protected]

Abstract—Innovative technologies, such as Software-Defined Networking (SDN) and Network Functions Virtualization (NFV), are enabling the possibility of managing network infrastructures and their services for enhancing network flexibility, efficient resource control, and cost-efficiency. How to combine these technologies requires taking into account the requirements established by the scenarios being executed, which can change at any time due to their dynamism. Network Slicing appeared to this end. This new technique tailors the needs of a particular scenario whose requirements are extremely heterogeneous and complex. By using Network Slicing, SDN/NFV-enabled environments can be strengthened to manage network resources and services depending on those requirements. Nevertheless, Network Slicing approaches lack management mechanisms that consider the heterogeneity and dynamism provided by scenarios based on future mobile networks. This article presents a formal definition of the Network Slicing information model, where all elements interacting with the Network Slices life cycle are formally represented. Another important contribution is a mobility-aware architecture that combines NFV/SDN techniques and introduces innovative components responsible for managing and orchestrating the Network Slices. Finally, a systematic comparison is made between the existing architectures and the proposed one. Index Terms—Network Slicing, Dynamic network management, Mobility-aware architecture.

more flexibility in provisioning services. Moreover, service providers achieve a significant improvement in the real-time administration of the infrastructure and provisioned services. The network management through SDN and NFV technologies is a hard task due to the heterogeneity of services and the diversity and dynamism of scenario requirements. In order to face this challenge, a particular technique called Network Slicing has been proposed [2]. The Network Slicing concept was introduced in 2010 referring to the possibility to combine network resources to enable their parallel use when sharing the same underlying physical infrastructure [3]. Some years later, with the goal of programming isolated Network Slices, a language semantics was defined that enables to modify the OpenFlow forwarding rules of network devices [4]. Nowadays, a Network Slice can be defined as a specific set of logical resources capable of providing certain services for diverse scenarios that demand different requirements.

I. I NTRODUCTION Communication networks are undergoing a radical change thanks to the recent introduction of innovative technologies, such as Software-Defined Networking (SDN) and Network Functions Virtualization (NFV). On the one hand, SDN is an approach to programmable networks built on the separation between the control and data planes. On the other hand, NFV decouples the software implementation of Network Functions (NF) from the underlying hardware. It enables the flexible and efficient control as well as deployment of virtual network infrastructure and services by providing availability, scalability, and efficiency. The combination of both technologies entails several advantages for network operators and service providers [1]. Network operators indeed benefit from the dynamism when managing their network resources and gain

VNF Manager

eHealth slice Ultra HD Video slice

Service Provider

Network Slice Blueprint Catalog

Domotic slice

Connected Vehicles slice …

Fig. 1: Network Slicing. Fig. 1 shows how the current proposals manage a Network Slicing environment. This environment comprises two

scenarios with different requirements: eHealth and Ultra HD video. The requirements of both services are not particularly challenging given the continuing advancing technologies. However, providing an adequate performance of these services based-on a spontaneous on-demand pattern is fairly challenging. Moreover, providing the high bandwidth required by the video service or the high availability of the eHealth with strict packet loss tolerances and high mobility is also difficult for the current networks, which are designed for best effort purposes. To meet the requirements of these scenarios the Service Provider checks the Network Slice Blueprint Catalog. Within that catalog, a given Network Slice Blueprint is the description of the structure, configuration, and workflows to instantiate and control the Network Slices during their life cycle. Once the catalog has been checked, the Network Slices that better fit the current scenario requirements are deployed, in this example, the eHealth and Ultra HD Video slices. For each slice, the Virtual Network Function (VNF) Manager makes use of a specific set of VNF sharing the same underlying infrastructure. Network Slicing can influence mobile networking directly, also prompted by the incoming fifth generation (5G) mobile technology. New scenarios are emerging in which such dynamism and flexibility have a fundamental role. Among them, the 5G Public Private Partnership (5G-PPP) identified the main Key Performance Indicators (KPIs) 1 regarding the network features to be achieved at an operational level: 10 to 100 times more connected devices, 1000 times higher mobile data volume per geographical area, end-to-end latency of less than 1ms, and ubiquitous 5G access including in low density areas. Recent research has focused on Network Slicing considering 5G networks, as the one proposed in [5]. Moreover, an integration of SDN architectures to enable the slicing is carried out in [6]. Despite the progress made by the previous solutions, to meet the dynamism, flexibility, and mobility considered by the 5G KPIs, a mechanism is needed that can manage dynamically the Network Slices and their resources by considering the current scenarios requirements. Indeed, we believe it is necessary to expand the current Network Slicing concept to strengthen it with mobility features, in order to achieve the network dynamism and flexibility required by the next generation of mobile technologies. Taking into account the potential of the previous technologies, this paper makes three main contributions: 1) A formal definition of the Network Slicing information model, where all elements interacting with the Network Slices life cycle are formally represented. The proposed model extends the definition of Network Slicing found in the literature by considering the mobility requirement, which the location of the Network Slices and their elements ensures. 2) A mobility-aware architecture that combines NFV/SDN techniques and introduces innovative components re1 Key

Performance Indicators defined by 5G-PPP, https://5g-ppp.eu/kpis

sponsible for managing and orchestrating the Network Slices. This architecture is built to consider the dynamism of an evolving scenario and the mobility of its internal elements. 3) An emergency use case where realistic concerns of current solutions are depicted. This use case also shows a systematic comparison between the existing architectures and the proposed one. The remainder of the paper is structured as follows. Section II discusses some related work on Network Slicing solutions as well as open challenges and requirements. Section III presents two information models that extend the current notion of Network Slicing. Section IV shows a realistic use case where different concerns of current solutions are depicted. Section V shows the components forming the proposed architecture in charge of managing the Network Slices and their elements. Finally, conclusions are drawn and future work suggested in Section VI. II. R ELATED WORK 5G networks need to integrate network services with different performance requirements (high throughput, low latency, high reliability, high mobility, and high security) into a single physical network infrastructure. 5G networks also need to provide each service with a customized logical network. In this context, network slicing has been proposed as one of the key technologies to achieve the previous goals. Different scenarios and use cases have been proposed in [7] with the goal of showing how the Network Slicing can improve their current challenges and requirements. Specifically, the authors highlight three scenarios: a Smart City scenario to manage the variety of different networks considered to acquire the information, where IoT networks are run by different departments with different access privileges; a Vehicle-ToEverything (V2X) scenario to provide precise knowledge of the traffic situation to optimize traffic flows, reduce congestion, and minimize accidents without forgetting the highly reliable communication required; and a E-health scenario to enable life-critical services that monitor the patients’ vital signs (e.g., heart rate, pulse, blood pressure etc.) in a reliable, fast, and secure way. In all of them, a smart-city network should be isolated from the public Internet. On the other hand, some key requirements for network slicing are defined in [8], such as network slicing resource specification to manage the description of the resources and network functions; guaranteed slice performance and isolation to enable the safe, secure, performance guaranteed service for multi-tenancy on the common physical networks; crossnetwork segment and cross-domain negotiation, so that each segment of the network may be further divided into different administrative domains; network slicing domain-abstraction to be aware and independent of the domain to which they belong; slice identification, associated with privacy and security characteristics of network slicing; and OAM operations with customized granularity, since different network slice users (operators, customers) will have different requirements.

Network Slice Ontology

hasLocation

Location isLocationOf hasCapability

hasMetric

Managed Element

Metric

Capability isCapabilityOf inherits

Mobility

PowerSettings

...

uses

User

SSP

CPUEff

inherits

isInstanceOf

uses

Service hasUser

hasService providedBy

Provider inherits

Network Operator

PktLossFreq

Network Slice

hasVNF

inherits

VNF

ConnErrRate

...

hasNFVI

composedBy

NFVI

inherits

Physical/Virtual Resource

Sub-NetSlice composedBy

3rd Party

Access Computation

inherits

...

Storage Connectivity

Network Slice Blueprint Ontology Fig. 2: The Network Slicing ontologies.

The authors of [9] present a 5G network slicing architecture together with a scheme for managing mobility between different access networks. Additionally, they also propose a joint power and sub-channel allocation scheme in spectrumsharing two-tier systems based on network slicing. Another architecture for next-generation networks is designed and implemented in [10]. This architecture lies on the concept of network function decomposition and network slicing. Specific network function blocks for forming network slices as well as their roles and requirements are defined in the proposed architecture. Finally, the authors also analyze the impact of the architecture on multiple tenants. The concept of Network Slice as a Service (NSaaS) was introduced in [11] with the goal of helping operators to offer customized end-to-end cellular network as a service. This work also illustrates how operators can configure and manage NSaaS and APIs for customers. Network slicing may impact several aspects of the 5G Radio Access Network like, for example, the protocol architecture, the design of network functions, or the management framework [12]. Regarding the efficient management of the elements making up the Radio Access Network (RAN) of 5G networks, a novel architecture is proposed in [13]. This architecture supports RAN slices according to the definition of a set of configuration descriptors that characterize the features, policies, and resources of radio protocol layers. The work described n [14] presents an energy-aware and policybased system oriented to the NFV and SDN paradigm, which allows managing the network infrastructure dynamically at run-time and on demand through policies. The authors of [15] propose an admission control mechanism to allocate network resources to different slices with the goal of improving the users’ satisfaction while ensuring the slices’ requirements. The authors performed some experiments that showed a higher user

experience in individual slices and a higher scalability with high amounts of users. Finally, the work presented in [16] described a resource allocation mechanism based on airtime assignment to achieve infrastructure sharing and slicing in WiFi Access Points. Its approach has the potential to be straightforwardly used within scenarios of wireless access infrastructure sharing. Despite the progress made by the previous solution a substantial body of work is still required in the definition and management of network slices given their mobility. In this sense, the proposed architecture introduces innovative components in charge of managing and orchestrating Network Slices as well as policies, in order to provide a flexible, efficient, and self-healing solution. III. N ETWORK S LICING F ORMAL M ODEL This section presents two ontologies that extend the current notion of Network Slicing. These are shown in Fig. 2. They are based on the common taxonomy proposed in [2]. To the best of our knowledge, the ontology-based formal models presented below are the first ones proposed in the literature, and they are based on the concepts and components found therein. A. The Network Slice Blueprint Ontology This ontology, shown in the bottom part of Fig. 2, combines concepts about NFV as well as the Network Slicing technique’s own concept. Its main class is NetworkSlice, which represents the instantiation of every element contained by the Network Slice Blueprint Ontology. A given NetworkSlice is responsible for the provisioning of Services and refers to a VNF, which comprises a set of logical resources, either physical or virtual, from the Network Functions Virtualization Infrastructure (NFVI). The NFVI class includes every kind of resource that can be used or deployed within a given IT

infrastructure, which can be related to computation, storage, or networking, for example. In an analogous manner, a SubNetwork Slice, defined as Sub-NetSlice, represents a way of reusing those fundamental Network Slices that provide similar features being shared by different NFs. The combination of all this information represents a Network Slice Blueprint, which is a type of template of how to deploy a Network Slice so as to meet the service requirements. The NetworkSlice class, together with Service and NFVI ones, are examples of ManagedElement from the upper ontology. Service Providers are represented by the Provider class, which is in charge of the provisioning of services. The Service class is relevant because it links all the concepts that describe the services being offered to users.

Users

Resources

(a) Initial scenario. Users

Services

Resources

(b) Emergency-driven scenario.

B. The Network Slice Ontology As shown in the upper part of Fig. 2, this ontology aims to manage the dynamism and mobility of critical components like NetworkSlices, NFVIs, and Services, all of them instances of the main class ManagedElement. It is worthy mentioning that all these elements included in both ontologies have been modeled following the Common Information Model (CIM) language, which has been formally defined by the DMTF as a standard [17]. CIM provides a common definition of management information for systems, networks, applications, and services. Because of that, all elements herein from the ManagedElement class, which is the main element for a given moden in CIM. The ManagedElement class identifies a generic entity that has some features, represented by the Metric, Location, and Capability classes. The Metric class refers to any indicator useful to measure the performance of the Network Slices and their elements. In the proposed use case, as discussed below, this indicator refers mainly to Quality of Service (QoS) values if the managed entity is a service. As proof of concept we have defined four different metrics: SSP, PktLossFreq, CPUEff and ConnErrRate. SSP is the sustained system performance, which focuses on measuring the Network Slice transaction speed. The Packet loss frequency (PktLossFreq) indicates the availability and QoS of the Network Slices communications, the CPUEff indicates the percentage of CPU used by the managed elements. Finally, the connection error rate (ConnErrRate) measures the reliability of the Network Slice and its elements. On the other hand, the Location class shows information about the position within the environment concerned. The Location class is the top-level class of a hierarchical model for location, having five predefined subclasses, namely (from low to high accuracy): Continent, Country, Region, City, and Position. These subclasses are not shown in Fig. 2 to ease its understanding. Position establishes the Geographical or Absolute Position of an element. The Capability class includes other subclasses such as PowerSettings and Mobility. While the former enables the optimization of energy efficiency, the latter has a key role when services are provided in highly dynamic environments, such as the one proposed in this article.

Services

Users

Services

Resources

(c) Post-mitigation scenario.

Fig. 3: The Emergency use case evolution.

IV. A M OTIVATING E XAMPLE : T HE E MERGENCY U SE C ASE This section shows a use case that highlight the issues of managing Network Slices without taking into account mobility aspects of the slices and their resources. Among the use cases identified by European research projects, some of them refer to emergency scenarios, where specific services must be prioritized to be always provided. In other words, this means that the dynamic reconfiguration or substitution of the Network Slices involved are guaranteed. For example, a use case is defined in the 5G NORMA project where parts of the network infrastructure are destroyed due to a natural disaster [18]. In our scenario, an unexpected event may occur at a certain moment, including natural disasters such as earthquakes, floods, or other unfortunate events like terrorist attacks. This scenario is represented through three different phases, as illustrated in Fig. 3. Specifically, Fig. 3 shows the ongoing evolution as follows: (a) the initial scenario, (b) when an emergency occurs, and (c) after the mitigation takes place. From left to right within every Network Slice, there are Users requesting Services that are provided by a set of Resources. In order to better understand each scenario of Fig. 3, consider that the resources currently assigned to a given Network Slice are represented in green, while resources that are not being used are shown in gray. Lastly, a red cross over an element suggests a status of failure. With regard to the services, the green arrow means the user can successfully access a given service, while the red one suggests the opposite. The positive

or negative outcome of the requests does not simply depend on the availability of the resources offered by the Service Provider, but also on which policies are currently regulating the access to such services. The update of those access policies is represented by the lock/unlock icon above the arrow. A. Initial Scenario: Normal Stage, No Emergency Initially, as shown in Fig 3a, a particular Network Slice called eHealth Slice, is deployed with enough resources to fit the requirements of the services. In that situation, the provisioning of services is working fine, as expected. Moreover, resources are not overloaded and users can access services without experiencing problems. Users are mainly represented by every member of healthcare staff working within all facilities for medical services and vehicles. Such services are accessing medical records, hospitalized patients’ locations, or a pharmacy warehouse. As might be expected, services have been provided according to conditions and policies specified by the eHealth Slice. This means that not every emergency member of staff (like doctors, nurses, firemen, and policemen) is granted with the access to each service. Here, the main issue (Concern 1) would be that some services experienced some worsening of the evaluation metrics. In this case, the management mechanism should trigger a dynamic adjustment of the Network Slices resources considering the users’ location and mobility, Network Slices, and their resources.

have in the initial scenario. In this context, the main issue (Concern 3), would be when the emergency finishes and a mechanism detects the new status of the scenario in order to deploy, change, and manage a new Network Slice located in the same place as the previous one. V. A M OBILITY-AWARE A RCHITECTURE TO M ANAGE N ETWORK S LICING The automation of the provisioning of innovative services needs to rely on an agile architecture able to adapt to a highly dynamic context. Fig. 4 shows the main elements of the proposed architecture, which has been developed starting from the ETSI reference model [19] whose components are represented on a blue background. Our contribution, which is shown in orange instead, manages the Network Slices and their resources dynamically with a policy-based and mobility-aware approach. Network Slice Management (NSMan)

OSS/BSS

Orchestrator

Automation Policy Engine

Network Slices NS

NS

NS

...

Network Slice Manager

B. Emergency-driven Scenario: An Emergency Occurs The second phase, represented in Fig. 3b, shows the occurrence of an unpredictable event that leads to serious issues with the provisioning of services and, potentially, to some hardware failures. For example, congestion is likely to happen when networks are still up, given the reduced capacity of the network linking hardware and the larger number of users located at a given place is trying to use online services. In this scenario, rescue teams, along with their instruments and vehicles, need critical connectivity. To properly solve this issue (Concern 2), there is the need for a special mechanism responsible for triggering corrective actions through dynamically changing the Network Slice. The location and mobility of the elements that make up the Network Slices needs to be taken into account to optimize the fixing measure. C. Post-mitigation Scenario: Network Evolved to Fix an Emergency Fig. 3c shows the last step in which an Emergency Slice is deployed as a response to the interruption of the delivery of services from the eHealth Slice. The new slice is provided with essential resources in order to be able to provide critical services to emergency and security personnel so that a stagnant scenario is avoided. In particular, since the service requirements have changed, the policies given by the Network Slice are different. In fact, now, the rescue teams are newly accessing the aforementioned services but, according to the specific policies defined in this context, they may have authorization to access some information that they would not

Virtual Network Functions (VNF) VNF

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... Virtualized Infrastructure Manager (VIM)

Virtualization sublayer Physical Resource

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Fig. 4: Main elements of the proposed architecture. In what follows Section V-A describes the elements proposed by the ETSI architecture, while Section V-B introduces our vision in detail. A. ETSI Architecture This section shows the elements that make up the proposed architecture in charge of managing the network slices given their mobility. From the bottom to the top, Fig. 4 shows that the Virtualized Infrastructure Manager (VIM) is responsible for the Network Functions Virtualization Infrastructure (NFVI) management as well as monitoring the resources. Specifically, the VIM is able to create, control, monitor, and dismantle the whole lifecycle of Virtual Machines (VM) instantiated

TABLE I: Examples of suitable metrics for the Network Slices management. Metric

Abbreviation Capacity

Scope

Packet Loss Frequency

PktLossFreq

Availability

Connectivity

Connection Error Rate (%)

ConnErrRate

Reliability

Connectivity

CPUEff

Transaction speed

Computation

SSP

Transaction speed

Overall performance

Instance Efficiency (%CPU peak) Sustained System Performance Provision Time (s) Total Acquisition Time (s) Communication Latency over SSL Supported Users on a Fixed Budget (#/$)

ProvTime

Resource acquisition time Elasticity

AcqTime

Resource acquisition time Elasticity

CommLatSSL Security, data security SupUserFB

on generic Physical Resources or equipment making up the network slices through the Virtualized Layer. The physical and virtual resources can range from computation and storage elements to SDN-oriented network infrastructure such as OVS switches and SDN controllers. At this point, it is worth mentioning that thanks to the functionality of the VF and VI managers, the proposed architecture is able to deploy, configure, and dismantle network slices with different resources according to the use case requirements. The Virtual Network Function Manager (VNFM) is in charge of the configuration, management, and monitoring of all the VNFs that make up the network slices. This manager is able to deploy, dismantle, and configure on-demand VNFs with the functionality provided by the network slices. The VNFs run on top of Virtual Machines (VS) exposed by the Virtualized Infrastructure. On the other hand, the SDN paradigm has the ability to decouple the data plane, where forwarding elements are located, from the control plane, where routing decisions are made; it also has the control element called SDN Controller, which manages multiple network elements belonging to the data plane, and the global administration perspective, which avoids making changes on individual network elements. In this regard, the SDN Controller allows the proposed architecture to control in real time the network communications between the elements of the network slices with the goal of ensuring aspects like such as security, privacy, and QoS. Lastly, the Orchestrator automatizes the management of the aforementioned elements. This component communicates with the VIM, the VNFM, and the SDN Controller to schedule their tasks as well as to receive information about the state of the scenario, thus updating its catalogs. Finally, the Orchestrator is linked to the Operations Support System/Business Support System (OSS/BSS) that serves the customer services.

Cost efficiency

Security Cost evaluation

inter-actions determined by the component take into account the policies defined by the network administrator as well as the slice context information and the location of the resources. Management policies are considered by the proposed architecture to control the slices as well as their resources dynamically. Policies are categorized in two different groups, intra-slice and inter-slice policies, managing the Network Slices life cycle dynamically but with a sharp difference. While the intra-slice ones are used to manage the elements of the slice itself, the inter-slice ones are responsible for switching from a given slice to a different one, due to the changing of some requirements of the service provided. The decisions made by the engine are then processed and automated by the Orchestrator, which we empower with innovative features. In fact, it becomes, in this case, responsible for the automation of the processes related to the Network Slices management based on the outcomes chosen by the Automation Policy Engine. TABLE I shows some examples of evaluation metrics that can be used to define policies. The first four have been used in the ontology of Fig. 2 where their class names are represented with abbreviations. Once an intra- or inter-slice policy is triggered, the Orchestrator communicates with the Network Slice Manager to perform corrective measures to the given slice. The Network Slice Manager manages the different Network Slices and SubNetwork Slices and it monitors their state. This information flows back to the Orchestrator in order to update the catalogs. The information considered by the Orchestrator and the Automation Policy Engine to perform the previous tasks is depicted in Fig. 5. The catalogs, resources, and instances managed by the ETSI model are shown on a blue background. Additionally, the catalogs, instances, policies, and ontologies introduced by our proposal to manage the Network Slices and their resources dynamically are shown in orange. VI. C ONCLUSION AND F UTURE W ORK

B. Network Slice Management (NSMan) The Network Slice Management (NSMan) includes several elements that directly deal with the life cycle of the Network Slices. These components, shown on an orange background in Fig. 4, represent a solution able to address the concerns about mobility, which have been discussed in the previous sections. The Automation Policy Engine is in charge of making decisions about the management of the slices. The intra- or

This article has presented a flexible mobility-aware solution to manage Network Slices thanks to the combination between SDN and NFV, considering the high dynamicity as a fundamental aspect of the service provision. These technologies can actually offer the necessary flexibility to evolve and adjust according to the continuously changing network scenario. The proposal, starting with a definition of an information model represented by two ontologies, is able to handle the

Orchestrator

Network Services Catalog

VNF Catalog

Network Slice Instances

Sub-Net Slice Instances

Automation Policy Engine

NFV Instances

NFVI Resources

Network Slice Blueprint Catalog

Mobility Policies

Network Slice Blueprint Ontology

Network Slice Ontology

Sub-Net Slice Blueprint Catalog

Fig. 5: Catalogs and databases of the proposed architecture.

Network Slices life cycle dynamically. For this purpose, first we propose a formal definition of the Network Slicing information model, where all elements interacting with the Network Slices life cycle are formally represented. This information model is managed by the novel mobility-aware architecture that combines NFV/SDN techniques and introduces innovative components responsible for managing and orchestrating the Network Slices. Finally, a realistic use case shows different concerns of current solutions and how the proposed architecture is able to address them. As future work, we plan to perform a first implementation of the proposal, also adding some means of predictive analytics for outage prevention and root cause determination, in order to get closer to an autonomic computing. In this sense we are currently implementing and validating the proposed architecture to show the time required to deploy, configure, and dismantle Network Slices as well as their elements and services. With this in mind, we are using: a) OpenStack as VIM to deploy and instantiate virtual machines and networks where the ICE Supervisor and the ICE Equipment Interfaces are running; b) OpenDaylight as SDN Controller to control both physical and virtual switches composing the network topology; and c) Open Baton to orchestrate the elements belonging to the SDN and NFV planes. By considering this environment, we plan to execute several actions aimed at ensuring the security, privacy, and QoS of the proposed emergency use case. ACKNOWLEDGMENT This work has been supported by a Séneca Foundation grant within the Human Resources Researching Postdoctoral Program 2018, the European Commission Horizon 2020 Programme under grant agreement number H2020-ICT-20142/671672 - SELFNET (Framework for Self-Organized Network Management in Virtualized and Software Defined Networks), and the European Commission (FEDER/ERDF). R EFERENCES [1] F. De Turck, R. Boutaba, P. Chemouil, J. Bi, C. Westphal, “Guest Editors’ Introduction: Special Issue on Efficient Management of SDN/NFVBased Systems - Part I,” IEEE Trans. Netw. and Serv. Manag., vol. 12, no. 1, pp. 1–3, Mar. 2015. [2] Next Generation Mobile Networks (NGMN Alliance), “Description of Network Slicing Concept,” NGMN 5G P1 Deliverable, Jan. 2016.

[3] R. Sherwood et al., “Carving Research Slices Out of Your Production Networks with OpenFlow,” ACM SIGCOMM Comput. Commun. Rev., vol. 40, no. 1, pp. 129–130, Jan. 2010. [4] S. Gutz, A. Story, C. Schlesinger, N. Foster, “Splendid Isolation: A Slice Abstraction for Software-Defined Networks,” 1st Workshop on Hot Topics in Software Defined Networks, pp. 79–84, Aug. 2012. [5] P. Rost et al., “Mobile Network Architecture Evolution Toward 5G,” IEEE Comm. Mag., vol. 54, no. 5, pp. 84–91, May 2016. [6] Open Networking Foundation (ONF), “TR-526 Applying SDN Architecture to 5G Slicing,” Issue 1, Apr. 2016. [7] K. Makhijani et al., “Network Slicing Use Cases: Network Customization and Differentiated Services,” draft-netslices-usecases-02 (Work in Progress), Oct. 2017. [8] L. Qiang et al., “Gap Analysis for Transport Network Slicing,” draftqiang-netslices-gap-analysis-01 (Work in Progress), July 2017. [9] H. Zhang, N. Liu, X. Chu, K. Long, A. H. Aghvami, V. C. M. Leung, “Network Slicing Based 5G and Future Mobile Networks: Mobility, Resource Management, and Challenges,” IEEE Comm. Mag., vol. 55, no. 8, pp. 138–145, Aug. 2017. [10] D. S. Michalopoulos, M. Doll, V. Sciancalepore, D. Bega, P. Schneider, P. Rost, “Network Slicing via Function Decomposition and Flexible Network Design,” 28th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, pp. 8–13, Oct. 2017. [11] X. Zhou, R. Li, T. Chen, H. Zhang, “Network Slicing as a Service: Enabling Enterprises’ Own Software-Defined Cellular Networks,” IEEE Comm. Mag., vol. 54, no. 7, pp. 146–153, July 2016. [12] I. da Silva et al., “Impact of Network Slicing on 5G Radio Access Networks,” 2016 European Conference on Networks and Communications, pp. 153-157, June 2016. [13] R. Ferrus, O. Sallent, J. Perez-Romero, R. Agusti, “On 5G Radio Access Network Slicing: Radio Interface Protocol Features and Configuration,” IEEE Comm. Mag., In Press, Jan. 2018. [14] A. Huertas Celdrán, M. Gil Pérez, F. J. Garc´ıa Clemente, G. Mart´ınez Pérez, “Policy-Based Management for Green Mobile Networks Through Software-Defined Networking,” Mobile Networks and Applications, In Press, Dec. 2016. [15] M. Jiang, M. Condoluci, T. Mahmoodi, “Network Slicing Management & Prioritization in 5G Mobile Systems,” 22th European Wireless Conference, pp. 1–6, May 2016. [16] M. Richart et al. “Resource Allocation for Network Slicing in WiFi Access Points,” 13th International Conference on Network and Service Management, pp. 1–4, Nov. 2017. [17] Distributed Management Task Force, Inc., “The CIM Standard: Common Information Model,” http://www.dmtf.org/standards/cim [18] EU H2020 5G NORMA Project, “Use Cases, Scenarios and Requirements,” Deliverable D2.1, Oct. 2015. [19] European Telecommunications Standards Institute (ETSI), “Network Functions Virtualisation (NFV); Infrastructure Overview,” ETSI GS NFV-INF 001 V1.1.1, Jan. 2015.