1. Huawei HCIP-Datacom-Core Technology V1.0 Training Material. In the module covering SDN, the documentation contrasts traditional network architecture with SDN. It explicitly states that traditional networks rely on device-by-device configuration and have coupled control and forwarding planes. In contrast, it defines SDN by its core characteristics: decoupled control and data planes, a centralized controller, and open northbound APIs that enable network automation and orchestration. (Refer to: HCIP-Datacom-Core Technology V1.0 Training Material, Chapter on SDN and Network Automation Basics, Section: "Comparison Between Traditional Networks and SDN Networks").
2. Kreutz, D., Ramos, F. M., Veríssimo, P. E., et al. (2015). Software-Defined Networking: A Comprehensive Survey. Proceedings of the IEEE, 103(1), 14–76. This peer-reviewed paper provides a foundational overview of SDN. In Section II-A, "The Genesis: Why Do We Need a New Network Architecture?", the authors state: "In a traditional network, the control and data planes are vertically integrated... Network operators are thus forced to manually configure each and every network device to implement a given network-wide policy... SDN proposes to decouple the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane)." This directly supports the statement's contrast. (DOI: https://doi.org/10.1109/JPROC.2014.2371999, Page 16, Section II-A).
3. Stanford University, CS244: Advanced Topics in Networking Courseware. The course materials, developed at the institution where SDN originated, consistently differentiate the two models. Lectures explain that the goal of SDN is to move from a complex, distributed control plane managed manually by network administrators to a logically centralized control plane that enables programmatic control, automation, and abstraction of network services. (Refer to: Stanford CS244, Lecture Notes on "Software Defined Networking," typically covering the limitations of traditional networks and the introduction of the SDN controller concept).