VNFs

Virtual Network Functions (VNFs) are software implementations of network functions that were traditionally delivered as dedicated hardware appliances, such as firewalls, routers, load balancers, and intrusion prevention systems. In the context of Network Functions Virtualization (NFV), VNFs run on standard servers and storage using virtualization or container technologies, enabling flexible deployment, on-demand scaling, and reduced capital and operating costs.

VNFs are deployed on NFV Infrastructure (NFVI), which provides compute, storage, and network resources, typically managed by a Virtualized Infrastructure Manager (VIM). The broader management and orchestration stack, often described as MANO (management and orchestration), includes the NFV Orchestrator (NFVO) that coordinates service lifecycle, the VNF Manager (VNFM) that handles the lifecycle of VNFs, and the VIM that controls the underlying resources. VNFs are designed to interoperate via standardized interfaces and can be composed into network services.

Standards for VNFs and NFV are defined by the European Telecommunications Standards Institute (ETSI) NFV ISG. Common VNFs include virtual routers, firewalls, NAT, load balancers, and virtualized EPC components. With the rise of cloud-native approaches, many operators are migrating toward containerized or cloud-native network functions (CNFs) that run on Kubernetes, but VNFs remain a core building block in many existing deployments. Key challenges include achieving near-line-rate performance, ensuring deterministic latency, multi-vendor interoperability, reliable lifecycle management, security, and observability.