Which of the following is NOT an advantage of Software-Defined Networks (SDN) over traditional networks?

The fundamental architectural principle of Software-Defined Networking (SDN) is the separation (or decoupling) of the control plane from the data plane. In SDN, network intelligence is logically centralized in a software-based controller (the control plane), which is separated from the underlying forwarding devices (the data plane). An integrated control and data plane, where each network device independently runs its own control logic, is the defining characteristic of traditional, non-SDN networks. Therefore, an integrated control plane is not an advantage of SDN; it is the legacy architecture that SDN is designed to replace.

A. Network logic is centrally integrated at the controller level: This is a primary advantage of SDN. Centralizing control logic provides a holistic, network-wide view, simplifying management and policy enforcement.

B. Applications communicate directly with the controller: This is a key benefit of SDN, enabling network programmability. Applications use northbound APIs to request network services from the controller, automating network behavior.

D. Greater agility in automating, monitoring, and provisioning network infrastructure: This is a direct result of SDN's centralized control and programmability. It allows for rapid, automated network changes and provisioning, which is a major advantage over traditional networks.

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1. Internet Engineering Task Force (IETF) RFC 7426: Software-Defined Networking (SDN): Layers and Architecture Terminology.

Section 1, Paragraph 3: "The key difference is that in a 'software-defined network', the control and data planes are decoupled, network intelligence and state are logically centralized, and the underlying network infrastructure is abstracted from the applications." This source directly confirms that SDN's nature is based on decoupling, not integrating, the control and data planes.

2. Nokia Nuage Networks: Virtualized Services Platform (VSP) Fundamentals Guide.

Chapter 1, "Introduction to SDN and the Nuage Networks VSP", Section "SDN architecture": This documentation describes the VSP architecture, which consists of a centralized control plane (VSC - Virtualized Services Controller) and a distributed data plane (VRS - Virtual Routing and Switching). This vendor-specific implementation exemplifies the core SDN principle of plane separation, contrasting with the integrated model of traditional networks.

3. Kreutz, D., Ramos, F. M. V., Veríssimo, P. E., Rothenberg, C. E., Azodolmolky, S., & Uhlig, S. (2015). Software-Defined Networking: A Comprehensive Survey. Proceedings of the IEEE, 103(1), 14-76.

Section II.A, "The Decoupling of Control and Data Planes", Paragraph 1: "The key idea is to decouple the control and data planes of network devices. The control plane logic is implemented in a logically centralized controller... The data plane is composed of simple forwarding elements..." This peer-reviewed publication establishes the separation of planes as the foundational concept of SDN. (DOI: https://doi.org/10.1109/JPROC.2014.2371999)