What is the meaning of Network Function Virtualization (NFV) ??
- NFV helps service providers to replace traditional Hardware appliances with software to achieve greater efficiency and reduce the cost.
- NFV allows software developed by the vendors to run on generic shared hardware, creating multiple touchpoints for management.
ETSI NFV Framework:
The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the telecommunications industry. Over the years ETSI has developed a number of standards/frameworks around NFV.ETSI NFV Framework standardizes NFV by defining the various elements required in virtualizing networking functions.
Infrastructure Layer:
The VNFs running on virtual hardware (virtual machines), emulated by the virtualization layer running on physical hardware.
NFV Infrastructure (NFVI):
The physical resources (compute, storage, network) and the virtualization layer that make up the infrastructure.
Computing hardware includes both the CPU and memory
Storage can be locally attached or distributed with devices such as NAS or SAN technologies
Networking hardware comprises pools of network interface cards and ports that can be used by the VNFs. The network also includes the data path for forwarding packets between virtual machines and across hosts.
The virtualization layer
It interacts directly with the pool of hardware devices, making them available to VNFs as virtual machines.
The virtual machine offers the virtualized computing, storage, and networking resources to any software that it hosts (VNF in this case) and presents these resources to the VNF as if they were dedicated physical hardware devices.
Virtualized Infrastructure Manager (VIM)
- VIM is part of MANO (Management and Orchestration blocks), Responsible for managing NFVI resources in “one domain” managing the computing, storage, and networking hardware, the software that is implementing the virtualization layer, and the virtualized hardware. (OpenStack can be considered as a VIM).
- Note the word “one domain” here. So there may be multiple VIMs in an NFV architecture, each managing its respective NFV Infrastructure (NFVI) domain.
- Because VIM directly manages the hardware resources, it has a full inventory of these resources and visibility into their operational attributes (such as power management, health status, and availability), as well as the capacity to monitor their performance attributes (such as utilization statistics).
- Manages life cycle of virtual resources in an NFVI domain. That is, it creates, maintains, and trminates virtual machines (VMs) from physical resources in an NFVI domain.
- Keeps inventory of virtual machines (VMs) associated with physical resources.
- Performance and fault management of hardware, software, and virtual resources.
- Keeps north-bound APIs and thus exposes physical and virtual resources to other management systems.
Virtualized Network Functions (VNF) Layer:
The VNF layer is where the virtualization of the network function is implemented. It comprises the VNF-block and the functional block that manages it, called VNF-Manager (VNFM).
Virtualized Network Functions (VNFs):
- IT represents a software implementation of a network function that is capable of running on top of the NFVI. the details of the virtualized environment are transparent to the VNF, and it is expected to be unaware that the generic hardware it is running on is actually a virtual machine.
- The network service being virtualized may be implemented through a single VNF, or it may require multiple VNFs. If, however, the network service requires VNFs to process the data in a specific sequence, then the connectivity between the VNFs needs to be defined and deployed to ensure it This is referred to service chaining.
Virtual Network Function Manager (VNFM):
- VNFM is to VNFs, what VIM is to NFVI as its main responsibility to bring up the VNF and manage the scaling of its resources.
- VNFM manages the life cycle of VNFs. That is it creates, maintains, scales, and terminates VNF instances. ( Which are installed on the Virtual Machines (VMs) which the VIM creates and manages)
- When the VNFM must instantiate a new VNF or add or modify the resources available to a VNF (for example, more CPU or memory) it communicates that requirement to the VIM. In turn, it requests that the virtualization layer modify the resources allocated to the VM that is hosting the VNF, Since the VIM has visibility into the inventory, it can also determine if it is possible for the current resource availability to these additional needs.
- The VNFM also has the responsibility for the FCAPS (fault, configuration, performance, accounting, and security) of the VNFs. It manages this directly by communicating with the VNFs or using the Element Management System (EMS) functional block.
- There may be one EMS per VNF or an EMS can manage multiple VNFs. EMS itself can be a VNF
NFV Orchestrator (NFVO):
- Has a critical and important role in the framework by generating, maintaining, and tearing down network services of VNF themselves. If there are multiple VNFs, the orchestrator will enable the creation of end-to-end service over multiple VNFs.
- In other words, NFVO has overlooked the end-to-end service deployment, parsing the bigger picture of service virtualization, and communicating the needed pieces of information to VIM and VNFM for implementing that service.
- NFVO also works with the VIM(s) and has a full view of the resources that they are managing. As indicated previously, there can be multiple VIMs and each one of them has only visibility of the NFVI resources that it is managing. Since NFVO has the collective information from these VIMs, it can coordinate the resource allocation through the VIMs.
- Similarly, the VNFM is independently managing the VNFs and doesn’t have visibility into any connection of the services between the VNFs and how the VNFs combine to form the end-to-end service path. This knowledge resides in the NFVO, and it’s the role of the NFVO to work through the VNFM to create the end-to-end service between the VNFs. It is therefore the NFVO that has visibility into the network topology formed by the VNFs for a service instance.
- NFV Orchestrator is also responsible for global resource management of NFVI resources. For example managing the NFVI resources i.e. compute, storage, and networking resources among multiple VIMs in the network. The Orchestrator performs its functions by NOT talking directly to VNFs but through VNFM and VIM.
VNF creation process:
- The full view of the end-to-end topology is visible to the NFVO.
- The NFVO instantiates the required VNFs and communicates this to the VNFM.
- VNFM determines the number of VMs needed as well as the resources that each of these will need and reverts back to NFVO with this requirement to be able to fulfill the VNF creation.
- Because NFVO has information about the hardware resources, it validates if there are enough resources available for the VMs to be created. The NFVO now needs to initiate a request to have these VMs created.
- NFVO sends requests to VIM to create the VMs and allocate the necessary resources to those VMs.
- VIM asks the virtualization layer to create these VMs.
- Once the VMs are successfully created, VIM acknowledges this back to NFVO.
- NFVO notifies VNFM that the VMs it needs are available to bring up the VNFs.
- VNFM now configures the VNFs with any specific parameters.
- Upon successful configuration of the VNFs, VNFM communicates to NFVO that the VNFs are ready, configured, and available to use.