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Siegfried Kiselev
Siegfried Kiselev

Network Function Virtualization: Concepts And A...


Network functions virtualization (NFV)[1] is a network architecture concept that leverages the IT virtualization technologies to virtualize entire classes of network node functions into building blocks that may connect, or chain together, to create and deliver communication services.




Network Function Virtualization: Concepts and A...



NFV relies upon traditional server-virtualization techniques such as those used in enterprise IT. A virtualized network function, or VNF, is implemented within one or more virtual machines or containers running different software and processes, on top of commercial off the shelf (COTS) high-volume servers, switches and storage devices, or even cloud computing infrastructure, instead of having custom hardware appliances for each network function thereby avoiding vendor lock-in.


The decoupling of the network function software from the customized hardware platform realizes a flexible network architecture that enables agile network management, fast new service roll outs with significant reduction in CAPEX and OPEX.


In October 2012, a group of telecom operators published a white paper[4] at a conference in Darmstadt, Germany, on software-defined networking (SDN) and OpenFlow. The Call for Action concluding the White Paper led to the creation of the Network Functions Virtualization (NFV) Industry Specification Group (ISG) [5] within the European Telecommunications Standards Institute (ETSI). The ISG was made up of representatives from the telecommunication industry from Europe and beyond.[6][7] ETSI ISG NFV addresses many aspects, including functional architecture, information model, data model, protocols, APIs, testing, reliability, security, future evolutions, etc.


A service provider that follows the NFV design implements one or more virtualized network functions, or VNFs. A VNF by itself does not automatically provide a usable product or service to the provider's customers. To build more complex services, the notion of service chaining is used, where multiple VNFs are used in sequence to deliver a service.


Ideally, therefore, virtualized functions should be located where they are the most effective and least expensive. That means a service provider should be free to locate NFV in all possible locations, from the data center to the network node to the customer premises. This approach, known as distributed NFV, has been emphasized from the beginning as NFV was being developed and standardized, and is prominent in the recently released NFV ISG documents.[12]


VNFCs should in general be able to scale up and/or scale out. By being able to allocate flexible (virtual) CPUs to each of the VNFC instances, the network management layer can scale up (i.e., scale vertically) the VNFC to provide the throughput/performance and scalability expectations over a single system or a single platform. Similarly, the network management layer can scale out (i.e., scale horizontally) a VNFC by activating multiple instances of such VNFC over multiple platforms and therefore reach out to the performance and architecture specifications whilst not compromising the other VNFC function stabilities.


Thus, NFV is not dependent on SDN or SDN concepts, but NFV and SDN can cooperate to enhance the management of a NFV infrastructure and to create a more dynamic network environment. It is entirely possible to implement a virtualized network function (VNF) as a standalone entity using existing networking and orchestration paradigms. However, there are inherent benefits in leveraging SDN concepts to implement and manage an NFV infrastructure, particularly when looking at the management and orchestration of Network Services (NS), composed of different type of Network Functions (NF), such as Physical Network Functions (PNF) and VNFs, and placed between different geo-located NFV infrastructures, and that's why multivendor platforms are being defined that incorporate SDN and NFV in concerted ecosystems.[18]


All network control functions in an NFV infrastructure can be accomplished using SDN concepts and NFV could be considered one of the primary SDN use cases in service provider environments.[20] For example, within each NFV infrastructure site, a VIM could rely upon an SDN controller to setup and configure the overlay networks interconnecting (e.g. VXLAN) the VNFs and PNFs composing an NS. The SDN controller would then configure the NFV infrastructure switches and routers, as well as the network gateways, as needed. Similarly, a Wide Area Infrastructure Manager (WIM) could rely upon an SDN controller to setup overlay networks to interconnect NSs that are deployed to different geo-located NFV infrastructures. It is also apparent that many SDN use-cases could incorporate concepts introduced in the NFV initiative. Examples include where the centralized controller is controlling a distributed forwarding function that could in fact be also virtualized on existing processing or routing equipment.


NFV has proven a popular standard even in its infancy. Its immediate applications are numerous, such as virtualization of mobile base stations, platform as a service (PaaS), content delivery networks (CDN), fixed access and home environments.[21] The potential benefits of NFV is anticipated to be significant. Virtualization of network functions deployed on general purpose standardized hardware is expected to reduce capital and operational expenditures, and service and product introduction times.[22][23] Many major network equipment vendors have announced support for NFV.[24] This has coincided with NFV announcements from major software suppliers who provide the NFV platforms used by equipment suppliers to build their NFV products.[25][26]


Virtualization is also changing the way availability is specified, measured and achieved in NFV solutions. As VNFs replace traditional function-dedicated equipment, there is a shift from equipment-based availability to a service-based, end-to-end, layered approach.[38][39] Virtualizing network functions breaks the explicit coupling with specific equipment, therefore availability is defined by the availability of VNF services. Because NFV technology can virtualize a wide range of network function types, each with their own service availability expectations, NFV platforms should support a wide range of fault tolerance options. This flexibility enables CSPs to optimize their NFV solutions to meet any VNF availability requirement.


ETSI has already indicated that an important part of controlling the NFV environment be done through automated orchestration. NFV Management and Orchestration (NFV-MANO) refers to a set of functions within an NFV system to manage and orchestrate the allocation of virtual infrastructure resources to virtualized network functions (VNFs) and network services (NSs). They are the brains of the NFV system and a key automation enabler.


Recent performance study on NFV focused on the throughput, latency and jitter of virtualized network functions (VNFs), as well as NFV scalability in terms of the number of VNFs a single physical server can support.[43]Open source NFV platforms are available, one representative is openNetVM.[44] openNetVM is a high performance NFV platform based on DPDK and Docker containers. openNetVM provides a flexible framework for deploying network functions and interconnecting them to build service chains. openNetVM is an open source version of the NetVM platform described in NSDI 2014 and HotMiddlebox 2016 papers, released under the BSD license. The source code can be found at GitHub:openNetVM[45]


Network functions virtualization (NFV) is the replacement of network appliance hardware with virtual machines. The virtual machines use a hypervisor to run networking software and processes such as routing and load balancing.


NFV allows for the separation of communication services from dedicated hardware, such as routers and firewalls. This separation means network operations can provide new services dynamically and without installing new hardware. Deploying network components with network functions virtualization takes hours instead of months like with traditional networking. Also, the virtualized services can run on less expensive, generic servers instead of proprietary hardware.


Essentially, network functions virtualization replaces the functionality provided by individual hardware networking components. This means that virtual machines run software that accomplishes the same networking functions as the traditional hardware. Load balancing, routing and firewall security are all performed by software instead of hardware components. A hypervisor or software-defined networking controller allows network engineers to program all of the different segments of the virtual network, and even automate the provisioning of the network. IT managers can configure various aspects of the network functionality through one pane of glass, in minutes.


Many service providers feel that the benefits of network functions virtualization outweigh the risks. With traditional hardware-based networks, network managers have to purchase dedicated hardware devices and manually configure and connect them to build a network. This is time-consuming and requires specialized networking expertise.


NFV allows virtual network function to run on a standard generic server, controlled by a hypervisor, which is far less expensive than purchasing proprietary hardware devices. Network configuration and management is much simpler with a virtualized network. Best of all, network functionality can be changed or added on demand because the network runs on virtual machines that are easily provisioned and managed.


NFV makes a network more responsive and flexible, and easily scalable. It can accelerate time to market and significantly reduce equipment costs. However, there are security risks, and network functions virtualization security concerns have proven to be a hurdle for wide adoption among telecommunications providers. Here are some of the risks of implementing network functions virtualization that service providers need to consider: 041b061a72


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