Understanding the Relationship Between SDN and NFV: Key Insights

Many developers often confuse SDN and NFV and cannot see their relationship. This article clarifies what SDN and NFV are and how they relate.

What is SDN

SDN (Software‑Defined Networking) virtualizes the network, turning the collection of devices into a software system whose core component is the SDN controller. The trend is to implement most network control functions in the controller without modifying the underlying forwarding devices.

The SDN controller can be viewed as a network operating system plus various control programs, while the hardware consists of network devices and links. Software components include the controller’s OS and control programs, as well as drivers embedded in network devices.

In providing virtual network services, rapid deployment of value‑added services and virtual network devices may require NFV to supply software‑based equipment that supports SDN’s fast response to customer needs.

The core concept of SDN is to turn a network into a software system; the controller does not distinguish whether the underlying device is a software‑based VNF or a hardware appliance.

What is NFV

NFV (Network Functions Virtualization) focuses on individual network devices, turning them into software. Traditional devices such as EMS/NMS, billing servers, authentication servers, DHCP, RADIUS, etc., are already pure software, while many others are embedded systems combining hardware and software (e.g., switches, routers, wireless equipment). These dedicated devices are chosen for performance, reliability, and cost considerations.

With increasing server compute power, most network devices—especially compute‑intensive ones (layers 4‑7)—can be replaced by servers running equivalent software. The rise of data centers and cloud computing drives the software‑based transformation of network equipment, offering faster service deployment, hardware generalization, reduced OPEX/CAPEX, and greater scalability.

NFV thus replaces dedicated hardware with pure software network devices.

Relationship between SDN and NFV

SDN is network‑oriented, turning an entire network into a software system; NFV is device‑oriented, turning individual devices into software.

NFV deployments need rapid network‑function provisioning and automation, which SDN provides; SDN itself does not depend on NFV.

SDN’s control plane manages both software and hardware devices. When delivering network services, SDN often requires rapid deployment of software devices (software routers, switches, VAS). NFV’s scope includes enabling those software devices.

SDN aims to software‑define, automate, simplify networks and reduce CAPEX/OPEX; NFV achieves device‑level softwareization, leveraging general‑purpose compute to replace dedicated hardware, thereby accelerating business innovation and lowering costs.

Conclusion

NFV relies on SDN’s automation capabilities to achieve fast deployment of network services.

SDN reshapes network architecture without changing functionality, while NFV reshapes device form without altering functionality.