Network Functions Virtualization (NFV) was founded by the European Telecommunication Standard Institute (ETSI) with Industry Specification Group (ISG) which contains seven of the world’s leading telecom network operators.
A challenge of large-scale telecom networks is increasing the variety of proprietary hardware and launching new services that may demand the installation of new hardware.
This challenge requires additional floor space, power, cooling, and more maintenance. With evolving virtualization technologies in this decade, NFV focuses on addressing the telecom problems by implementing network functions into software that can run on server hardware or hypervisors.
Furthermore, by using NFV, installing new equipment is eliminated and it will be related to the health of underlay servers and the result is lower CAPEX and OPEX.
There are many benefits when operators use NFV in today’s networks. One of them is Reducing time-to-market to deploy new services to support changing business requirements and market opportunities for new services.
Decoupling physical network equipment from the functions that run on them will help telecom companies to consolidate network equipment types onto servers, storage, and switches that are in data centers. In NFV architecture, the responsibility for handling specific network functions (e.g. IPSEC/SSL VPN) that run in one or more VM, is Virtual Network Function (VNF).
Figure 1 - NFV Infrastructure
As figure 1 depicts, the whole system of NFV that contains physical and virtual components is called NFV Infrastructure (NFVI). NFVI can be different based on deployments and the vision of a service provider. For example, NFVI can build upon Docker or maybe a kind of hypervisor or mixing of both of them.
Service Provider NFV Deployment
Service Providers may use their own OSS/BSS to provision their infrastructures and boost service hosting to their customers and users. Based on this approach, there should be other protocols and components that help Service Providers to build their end-to-end full automated services using NFV. To meet this demand, ETSI released a framework that shows functional blocks and reference points in the NFV framework.
The main reference points and execution reference points are shown by solid lines and are in the scope of NFV. These are potential targets for standardization. The dotted reference points are available in present deployments but might need extensions for handling network function virtualization. However, the dotted reference points are not the main focus of NFV at present. Figure 2 illustrates the ETSI NFV framework architecture that is taken from the ETSI document.
Figure 2 - ETSI NFV Framework
A key component in the NFV architectural framework is the virtualization layer.
This layer abstracts and logically partitions physical hardware resources and anchors between the VNF and the underlying virtualized infrastructure.
The primary tool to realize the virtualization layer would be the hypervisors. The NFV architectural framework should accommodate a diverse range of hypervisors.
On top of such a virtualization layer, the primary means of VNF deployment would be instantiating it in one or more VMs.
Therefore, the virtualization layer shall provide open and standard interfaces towards the hardware resources as well as the VNF deployment container, e.g. VMs, in order to ensure independence among the hardware resources, the virtualization layer, and the VNF instances. VNF portability shall be supported over such a heterogeneous virtualization layer.
The decoupling of a VNF from the underlying hardware resources presents new management challenges. Such challenges include end-to-end service to end-to-end NFV network mapping, instantiating VNFs at appropriate locations to realize the intended service, allocating and scaling hardware resources to the VNFs, and keeping track of VNF instances location, etc.
Such decoupling also presents challenges in determining faults and correlating them for a successful recovery over the network.
While designing the NFV Management and Orchestration, such challenges need to be addressed. In order to perform its task, the NFV Management and Orchestration should work with existing management systems such as OSS/BSS, hardware resource management system, CMS used as a Virtualized Infrastructure Manager, etc., and augment their ability in managing virtualization-specific issues. Also, SDN (Software Defined Network) can bring agile and lower provisioning time to the network alongside NFV.