What are Virtual Network Functions (VNF)?

Cloud technology is seen as the technology of the future and is quickly becoming the norm for all service providers and telecom operators attempting to operate more effectively and give superior service. To transition historical networks into software-based and service-oriented networks, software-based technologies such as Network Functions Virtualization (NFV) and Software Define Network (SDN) are seen as essential.

Virtual Network Functions (VNF) that run and deploy more quickly and rapidly on a private cloud or one of the public clouds (e.g. Google Cloud Portal, Amazon Web Services, Azure, etc) than traditional networks allow service providers to manage a flexible and dynamic network and automate the deployment of the service, making it quicker, cheaper, and more efficient.

VNFs assist improve the scalability and agility of a network, while also allowing more efficient use of infrastructure resources. Since VNFs replace real hardware, other advantages include a reduction in power consumption, an increase in security, and an expansion of available physical space. Additionally, operating and capital costs are minimized.

In this article, we will discuss the following topics:

• What does VNF Stand for?
• What is the Main Function of the VNF manager?
• What is VNF Architecture?
• What is the Importance of VNFs?
• What are the Advantages of VNF?
• What are the Challanges of VNF?
• What are the Examples of Virtual Network Functions?
• How Does VNF Work?
• What are the Differences Between VNFs and PNFs?
• How does VNFs Differ from NFV?
• What are the Differences Between VNFs and CNFs?
• How to Select VNF Manager?

What does VNF Stand for?

Virtual Network Functions (VNFs) are network services that were previously executed by proprietary, dedicated hardware technology but are now executed on open computing platforms via virtualization. Virtualized routers, load balancers, directory services, firewalls, wide area network (WAN) optimization, and network address translation (NAT) services are typical VNFs.

Individual network and network security tasks are migrated from specialized hardware devices to software that operates on commodity hardware by means of VNFs. Virtual network functions allow organizations to build standard networking hardware components completely in software. Network service providers and companies utilize load balancers, firewalls, routers, Domain Name System (DNS), network address translation (NAT), intrusion detection, caching, Quality of Service (QoS), and Virtual Private Network (VPN) to accomplish these functions. VNF enables enterprises to adapt to business demands with more agility and to be less susceptible to service outages. Virtual network functions (VNFs) operate inside virtual machines (VMs) or containers on standard virtualization infrastructure software like VMWare or KVM. Multiple VMs may exist on a single physical unit, using all of its resources. The administration and orchestration of VNFs are performed inside the NFV (Network Functions Virtualization) framework.

A network function (NF) is a fundamental component of a network design with predefined external interfaces and behavior. This might consist of a network node or a physical device, such as a firewall. A virtual network function is a software implementation of a network function that is readily deployable on virtual machines and other virtual resources (VMs).

Software-defined networking (SDN) implementations rely heavily on virtual network functions (VNFs). The term "virtual" in VNF is rather deceiving, since VNFs do not really provide the same functions as other virtual network services. They instead represent software products with comparable purposes. However, rather than being deployed on specialized hardware or equipment operating inside a data center, these apps operate solely on the data center servers.

Virtual network functionalities have received considerable commercial momentum. They offer a platform for providing secure, flexible services while allowing state-of-the-art business models at a cheaper cost and with more flexibility than typical monolithic hardware-centric legacy systems. They are essential for enterprises designing next-generation service architectures. In a technique called as service chaining, VNFs may be interconnected like building blocks. Although the idea is not novel, service chaining and the service provisioning/deprovisioning operations are streamlined and VNFs offer significant scalability.

Adding network capabilities such as firewalls, switching, WAN optimization, and load balancers to a data center increases cost and complexity. These functions are migrated to software-based virtual network functions that isolate each function from the underlying proprietary hardware and maintain them operational regardless of physical environment faults.

What is the Main Function of the VNF manager?

The VNF manager is an essential component of virtual infrastructure management, since it must standardize virtual network functions and facilitate interoperability between software-defined components. The VNF Manager is responsible for the lifecycle management of virtual network functions, which includes instantiation and termination of network functions, scaling of network functions, software upgrades of VNFs, configuration of various complexities, and receipt of performance measurements and alarms at the VNF level.

Scaling network functions involve scaling in/out (raising and reducing the number of VNFs) and scaling up/down (increasing or lowering the amount of resources, such as RAM or vCPU) based on the requirements. The VNF Manager may be built for the same VNFs, other VNFs, a single VNF instance, or many VNF instances, as well as for more complicated VNFs such as vIMS or vEPC.

What is VNF Architecture?

As essential components of network functions virtualization (NFV) architecture, VNFs are constructed on top of NFV infrastructure (NFVI), which includes a virtual infrastructure manager (VIM) to effectively distribute resources such as storage, computation, and networking among VNFs. The management, automation, and network orchestration (MANO) features offered by NFV serve as the basis for operating NFVI and delivering new VNFs.

Figure 1. VNF Architecture

What is the Importance of VNFs?

Due to their hardware-centric architecture and lack of programmability, old physical networks are somewhat stale by current data center standards despite their importance to business operations. Typically, network orchestration involves the deployment of network resources using a command-line interface (CLI) or simple scripting tools. This infrastructure comprises of closely interconnected private hardware and software. All of this proprietary technology results in a network that is difficult to obtain, inflexible, and expensive to run.

With the current wave of private and public infrastructure-as-a-service offerings, there is a huge industry push to automate the provisioning and setup of on-premise and cloud-based applications and infrastructure. This tendency is leading to an entirely new paradigm of IT automation. This automation is to allow IT firms to dynamically provide any application or connection from a centralized control center at any location, hence enhancing business agility. This trend is motivated by the aim to decrease operating costs, increase performance via automation, and simplify network administration by deploying as little software as possible.

Demand for network programmability and adaptability is driving industry development. Telecom service providers and other major organizations are implementing virtualization technologies such as SDN and NFV to achieve ever-increasing ROI and productivity. The shift to a flexible, dynamic, and programmable business cloud services architecture is driven by open-source software. Standard hardware platforms have been employed in a software-defined data center (SDDC).

VNFs are virtualized network services that provide programmability at a higher level by encapsulating a whole physical or software-defined layer inside a virtual package. They are capable of providing network services, as opposed to physical devices such as routers or switches. The purpose of VNFs is to assist clients in expanding their networks by providing them with tools that provide more flexibility, enhanced security, and cheaper prices than conventional hardware appliances.

VNFs connect conventional telecom networks to software-defined networks. The change entails the replacement of proprietary hardware and restricted APIs for hardware interfaces with cloud infrastructure and open interfaces for external applications. The VNF paradigm symbolizes a transition from vertically integrated, closed systems to an open, converged infrastructure that enables the delivery of IT services with more flexibility.

What are the Advantages of VNF?

Traditionally, new services and network operations are deployed and manually setup on proprietary hardware. Network engineers enable and configure certain appliance features. With service chaining, for instance, engineers would have to manually connect each specialized equipment to link certain tasks so that they execute in the proper order. VNFs virtualize these tasks in software, allowing new functions to be delivered more rapidly and effectively as VMs or containers. The lifecycle of a VNF is shorter and more dynamic due to the fact that functions are regularly added and quickly given via the use of automated software solutions that do not need onsite intervention. This virtualization architecture reduces the need for costly hardware designed for a specific purpose.

VNFs may assist improve the scalability and adaptability of a network, while also allowing more efficient use of network resources. VNFs enable organizations to download, move, upgrade, delete, activate/deactivate, and scale any network location up/down with a single click. This delivers a highly available and readily expandable architecture.

Other VNF advantages include those listed below:

• a reduction in both operational and capital expenses over the long run

• a reduction in power and cooling needs

• a reduction in the amount of physical data center space needed as VNFs replace physical hardware

• a reduction in total power consumption

What are the Challanges of VNF?

Even though ETSI has standardized NFV as a technology, there is a lack of clarity in the function distribution on the MANO layer, such as between the e NFV Orchestrator (NFVO) and the VNF Manager. This fosters an atmosphere conducive to creativity and supports the advancement of technology. However, this results in diverse interpretations of standards by different vendors, distinct product implementations, and random placement of functions throughout the orchestration layer. If NFV/VNF suppliers do not adhere to standards in the future, telecom service providers and corporations may encounter complications when deploying nonstandards-based NFV designs and VNF deployment templates.

When selecting a VNF Manager, there are two options: dedicated per a single VNF or a generic VNF Manager that can handle the lifecycle management of numerous VNFs (raising the number of northbound integrations towards NFVO and southbound integrations towards VIM). Consequently, the selected strategy impacts the extent of automation and the complexity of the setup, particularly if there are vendor-specific features. In a multi-vendor context, different vendor interpretations might result in the duplication of functionality. Using a generic VNF Manager considerably reduces the complexity of MANO since it eliminates the need to handle many VNFMs. However, this result in vendor lock-in, in which a provider becomes excessively reliant on a single solution.

Moreover, in the first shift from physical components to virtual network functions (VNFs), suppliers often removed all embedded software systems from appliances and formed a single huge VM. Without optimizing these virtual machines, they constructed inefficient, single-purpose virtual appliances that were difficult to administer and maintain.

Consequently, it is essential to have a management system capable of handling frequent VNF lifecycle modifications. To accomplish appropriate automation, it is also essential to establish a standardized method of modeling VNFs. Otherwise, the functioning of VNFs will be fraught with confusion and errors.

Additionally, with these sorts of outdated VNFs, it is challenging to achieve scalability in cloud settings. Many service providers have embraced a single, horizontal NFVI cloud platform in order to simplify their infrastructures for operating many VNFs. These modifications enable NFV to function as a basic technology for 5G and edge networks. Still, the "weight" of VMs might hinder the performance of VNFs in large-scale 5G or edge deployments that need agility, scalability, and reduced overhead.

VNFD (Virtual Network Function Descriptor) and an automation component are essential for modeling virtual network functions (VNFs). VNFD describes operational instructions, policies, lifecycle automation for a specific VNF, auto-scale options, performance indicators, rules and triggers, while the automation component creates and executes an automation routine.

The latter additionally handles exceptions and potential process failures.

Beyond issues about uniformity, additional VNF problems are as follows:

• To replace physical network functions (PNFs) with virtualized functions, VNFs need a large infrastructure investment up front.

• The layered software design of VNFs may obscure security visibility and traceability, hence posing additional cybersecurity concerns.

• When utilizing conventional network monitoring technologies, network teams risk lose monitoring and management visibility.

• Building and managing VNFs in virtualized hypervisor or container systems requires network teams to overcome a deployment and management learning curve.

• Multi tenancy is not supported.

• Built, configured, and tested to operate on NFV hardware infrastructure.

• Need a great deal of hardware to be easily accessible.

• There are no APIs available to enable automatic scaling and configuration in response to the unexpected resource use spike.

• No architectural standards

• No vendor-specific protocols or configuration policies

What are the Examples of Virtual Network Functions?

Examples of frequently used VNFs include:

• Security features: Security measures include firewalls, intrusion detection systems (IDS), virus scanners, and spam protection

• Edge devices: Broadband remote access server (BRAS), virtual customer premises equipment (vCPE), and IP Edge are examples of Edge devices.

• Switching: Broadband network gateway (BNG), carrier-grade network address translator (CG-NAT), and routers are used for switching.

• Gateway tunneling elements: Gateways for IPSec/SSL virtual private network (VPN)

• Network-wide capabilities: Authentication, Authorization, and Accounting (AAA) Platforms for Policy Control and Charging

• Application-level optimization: Content delivery networks (CDNs) and load balancers are used for application-level optimization.

• Traffic analysis: Deep packet inspection (DPI) and quality of experience (QoE) measurement include traffic analysis.

• Signaling: IP multimedia subsystem and session boundary controllers (IMS)

How Does VNF Work?

In a layered network paradigm, a virtual network function is a standardized grouping of hardware and software components that performs a single service function unit. VNFs function as software-only instances of virtual machines on regular hardware. A routing VNF, for instance, implements all the functions of a router, but operates in software-only mode on generic hardware.

Each VNF has its own instance of the operating system (OS). Compared to a containerized environment, a VM instance's startup time may be slower. Each VNF's application functionality resides solely inside its own VM. This enables threads to communicate with one another with little overhead.

Both NFV and VNF virtualization provide the implementation of NFs in a way that is independent of the underlying device. VNFs are compatible with all VM environments, including branch offices, the cloud, and data centers.

VNFs architecture allows you to:

• Improve application performance. For instance, a VNF may be used for security or traffic priority. The network traffic between the user and the cloud application is routed through the shortest path.

• Place network services in the most secure location possible. For instance, a company may establish a VNF firewall at a branch office rather than pay the inefficiencies of an MPLS connection to funnel traffic through a firewalled data center located far away.

VNFs are controlled and coordinated as part of the infrastructure for virtualizing network operations. VNFs are often performed on VMs controlled by operators using best practices and VM orchestration tools. On COTS (Commercial off-the-shelf) servers, VM-based VNFs are surrounded by a guest OS/kernel, hypervisor, host OS/kernel, and network I/O.

Except for speed and scalability, VNFs replicate a number of the capabilities and characteristics of physical network functions (PNFs), subject to the adjustments required for operation in virtual environments.

VNFs operate flexibly with other VNFs in the cloud, enabling clients to more efficiently manage their resources. As a software program, a virtual server host several VNFs that are activated and deactivated as necessary. Through a technique known as service chaining, these VNFs are joined together as building blocks. VNF technology expedites and simplifies service chaining, despite the fact that the idea is not novel.

What are the Differences Between VNFs and PNFs?

Historically, service providers and corporations have built their network infrastructures on purpose-made hardware and software. These components, also known as physical network functions or PNFs, often use customized appliance hardware with application-specific integrated circuits for best performance. Firewalls, load balancers, routers, switches, and DNS and Dynamic Host Configuration Protocol servers are examples of PNF appliances.

VNFs provide the operation of various networking services, but decouple them from proprietary hardware. Instead, network functionalities are supported on commodity hardware by means of a software layer that emulates network-specific hardware processes. The vast majority of VNFs are deployed as virtual machines (VMs) using Linux KVM or VMware vSphere hypervisors on commercially available hardware. Physical network function (PNF), in contrast to Virtualized Network Functions (VNF), refers to older network appliances on proprietary hardware.

In a number of instances, service providers, telecom operators, and businesses are introducing VNFs by replacing old PNF hardware with virtualized equivalents.

How does VNFs Differ from NFV?

Historically, service providers were the first to see the potential of virtualized operations to streamline provisioning and facilitate customer service customisation. Deutsche Telekom, AT&T, BT, Verizon, Orange, Telecom Italia, and Telefonica proposed the notion of Network Functions Virtualization (NFV) at the SDN and OpenFlow World Congress in 2012. ETSI was responsible for NFV development and standardization, and in 2013 the organization established the ISG for NFV to manage NFV standards and recommendations.

Although NFV and VNF are sometimes used interchangeably, the terminology have distinct meanings. Individual VNFs are the core component of an NFV architecture as a whole. NFV consists of NFV management and orchestration (MANO) and NFV infrastructure as well.

The framework for managing and orchestrating VNFs is NFV MANO. The NFV infrastructure contains both software and hardware computation, storage, and networking components. This architecture supports the virtualization of functions. All of these NFV components must then interface with existing billing and operational systems.

What are the Differences Between VNFs and CNFs?

VNFs have traditionally been delivered utilizing virtual machines. Virtual machines need a different server operating system (OS) for each network function, while being significantly more efficient than PNFs. This design tends to utilize more central processing unit/memory resources than required, restricting the capacity of a provider or company to deploy services horizontally for enhanced performance.

The term cloud-native network functions (CNFs) describes a relatively recent development in this field of technology. CNFs were created to solve the issue that VNFs encounter while offering agile and scalable network services in a distributed, multi-cloud, or edge computing architecture.

By using centralized and dispersed locations for application hosting, enterprises with cloud-native capabilities enjoy enhanced flexibility, scalability, reliability, and mobility. Moving beyond virtualization to a truly cloud-native architecture increases the efficiency and agility necessary to rapidly deploy fresh, consumer-desired solutions.

A cloud-native virtual network function (VNF), sometimes known as a cloud-native network function (CNF), is a VNF designed for the evolving cloud environment. CNFs are distinct from VNFs because, unlike VMs, they were intended to function inside cloud or edge containers. Multiple network services run independently in separate containers that are controlled and managed by a single server operating system. This is the primary distinction between virtual machines and containers. Consequently, CNFs need even less operating resources, reducing the cost of deploying services across various clouds and in edge computing settings.

CNFs are designed and configured for container execution. This containerization of network architectural components allows several services to operate on the same cluster and facilitates the onboarding of pre-decomposed applications, while dynamically routing network traffic to the corresponding pods.

The use of containers rather than virtual machines (VMs) is a distinguishing feature of the cloud-native approach. Containers allow users to encapsulate software (apps, functions, or microservices) together with the necessary files to run them. They let access to the OS and other server resources to be shared. This method makes it straightforward to transport an encapsulated component across contexts while preserving its functionality.

By encapsulating network operations into containers, CNFs circumvent a number of the fundamental limitations of VNFs. The containerization of network components enables enterprises to regulate how and where network nodes perform operations.

The creation of cloud-native VNFs is a cost-effective alternative for organizations, and the presence of all cloud-native characteristics in VNFs represents a revolution in software development. Self-management and scalability are among the most notable distinctions between cloud-native VNFs and conventional VNFs.

How to Select VNF Manager?

To enable a cloud-native architecture, a typical VNF Manager must allow automation, rapid deployment, and upgrades and updates for VNFs. In addition, it must provide simplified administration and simple scalability based on service demand, all at a reasonable price.

Due to the absence of industry standards, the majority of suppliers are led by these needs, yet end up delivering varying solutions. Therefore, it is important to choose a VNF Manager that can be incorporated into any VNF independently. In this manner, a solution may execute all general operations and deal with automation, setup, and scalability out of the box. Using solutions that cooperate with other manufacturers and service providers via various organizations or open-source software help to overcome a lack of standardization. On this basis, cloud-native functionality is provided out of the box, since the VNF Manager has previously been tested with many vendor-specific VNFs. ONAP (Open Network Automation Platform) is an excellent example of such an open-source platform, since it is backed and promoted by key companies.

Since the VNF Manager is a key component of MANO (NFV Management and Orchestration), interoperability and integration should be thoroughly investigated. And since many service providers use a multi-vendor environment, a generic VNF Manager is an excellent way to manage all VNFs inside a single domain from a single place. This further reduces the number of northern and southbound interface integrations.

Achieving such a universal configuration management, in which VNFs are configured using a standard VNF model, enables service providers to better manage modeling and service automation difficulties. Using a model-based language like as TOSCA, VNF topologies, interfaces, lifecycle events, and virtual infrastructure needs may all be expressed using templates to achieve such a universal setup. Templates are not tied to a particular infrastructure or VIM and are utilized several times with other VNFs. They describe service components, the connections between service components, and the many dependencies and capabilities of each component, making it simpler to model each VNF in the same universal way and facilitating the setup of a large number of VNFs.

VNF Managers that offer an open-source solution are also ideal for resolving any issues with proprietary vendor deployment, hence facilitating the usage of VNF Managers for a variety of VNFs.