# 5G Support for Industrial IoT Applications--Challenges, Solutions, and Research Gaps
## 3 A Brief Overview of 5G
### SDN, NFV and Resource Orchestration Approaches in 5G  
The trend of virtualization leads to the appearance of cloud-native applications and infrastructure managers that ensure the seamless operation of those applications. Today's most widely used resource and service managers, e.g., Kubernetes [14] that manages containers primarily for web applications, provide automatic scheduling, scaling, and self-healing features. Most of these solutions, however, target solely data centers, and are not designed for a geographically distributed infrastructure. Moreover, they often fail to employ such scheduling policy that guarantees the low latency the novel applications demand.  
A dedicated component, namely, the resource orchestrator (RO), is in charge of managing the underlying resources and finding the proper placement of software components realizing the service. Following ETSI's terminologies on Network Function Virtualization (NFV) [15], the software modules composing the network service are referred to as Virtual Network Functions (VNFs).  
VNF (and NFV) is often mentioned together with Software Defined Networking (SDN), especially when discussing 5G core network resource optimization and slicing [16]. On one side, SDN is originated from the telecom operators' domain with the intent of separating the rigid and interdependent structure of control and forwarding planes in networking equipment. On the other hand, VNF/NFV has emerged from the data center and resource optimization community aiming to provide flexibility in the network functions. These communities nowadays work together in solving challenges brought by the requirements of 5G slicing [17]. The main concepts and respective challenges have recently been summarized in [16].  
A key element of this infrastructure is the resource orchestrator, which can be considered as a component encompassing orchestration related tasks, and in ETSI's architecture it appears both in the  
Figure 3: An architectural view of the 5G network slicing [13].  
Virtual Infrastructure Manager (VIM) and in the NFV Orchestrator (NFVO). In general, RO assigns VNFs composing the service to compute resources and also allocates paths between connected VNFs.  
A novel RO (or a hierarchy of ROs) that can efficiently manage underlying resources in cloud-edge/mobile edge/distributed cloud computing environments is an inevitable future component with challenging tasks. It must be able to jointly handle compute and network resources in a tightly integrated framework and it must be aware of network characteristics besides compute capabilities. Furthermore, the requested network services have to be created on-the-fly within seconds. Two different design approaches can be applied to achieve such features. On the one hand, on top of VIMs and network controllers, a higher level orchestrator, i.e., the NFVO, can be added which is able to integrate different resource domains. This solution results in a hierarchy of ROs and the cooperation of VIMs and NFVO yielding larger deployment time and the need for strictly defined external APIs. Multi-provider scenarios require this approach. On the other hand, the VIM itself can be extended with network awareness and with the detailed view on network resources. With such an upgrade, the additional NFVO becomes unnecessary for single-provider setups where resources belong to the same operator and by these means, the orchestration and deployment time can be reduced significantly [18].