Next Generation Wireless Networks: Software Defined Networks
To explain the subject more effectively, let’s consider a scenario: My job involves transmitting data and managing this process through message types. There are various devices at each layer that control these messages. These devices are situated across different layers, and we purchase and operate them according to their functions.
For instance, a laptop is just a device that operates based on the applications installed on it. I can not use it as a base station. To connect to Netflix, everyone needs to connect to a base station, which inevitably creates a bottleneck. Therefore, we propose that devices should be simplified ("dummy") and have a Control Plane layered above them.
Under this approach, I will assign rules to these devices, and they will act according to these rules. Controllers will communicate with the devices at specific intervals, but afterward, the devices will operate independently based on their own intelligence and the predefined rules—without requiring constant communication with the controller. This concept is known as software-based architecture.
Figure 1: Legacy Network Architecture
“Software” Defined Network Management
- The goal of SDN is to provide open, user-controlled management of the forwarding hardware in a network.
- SDN exploits the ability to split the data plane from the control plane in routers and switches.
- “he control plane can send commands down to the data planes of the hardware.
- This paradigm provides a view of the entire network, and helps to make changes globally without a device-centric configuration on each hardware unit.
One of the key ideas here is global centralization. Previously, each device had its own "brain." With the new approach, we removed the individual intelligence from devices and centralized it into a single "big brain" at the top. In this model, the operating systems and application programs that were once inside the devices have been moved to the controller at the top, making it the central intelligence. The devices themselves are reduced to their basic components—essentially just their ports and forwarding hardware. As a result, these devices become "dummy" devices, forming what is now called the Data Plane.
Multi-Tenancy: Multi-tenancy refers to the management of servers that perform multiple tasks—such as routing, switching, DNS, and more—by centralizing their operations under one controller at the top.
Virtualization: Virtualization is the underlying structure that enables the transition from hardware-based operations to software-based ones. In device virtualization, hardware components like the CPU, RAM, I/O, and hard drives are shared among applications. Similarly, in network virtualization, resources such as cables, switches, routers, bridges, firewalls, and DNS are shared. This ensures the effective utilization of network resources. In the past, I would purchase a physical device and connect it to my network, virtualizing it locally. However, that agile and fast structure of hardware is no longer part of this model.
Application to Daily Use
For example, when I go home, my phone will no longer directly connect to Wi-Fi or 4.5G. Instead, the controller will manage the connection for me, ensuring seamless internet access at all times. I won’t even need to know who or what I’m connecting to—the controller will handle it all.
Advantages and Challenges of SDN
Software-Defined Networking (SDN) introduces a more centralized structure with significant advantages, despite some gaps. Over time, as requests from various locations increased in both frequency and intensity (spatially and temporally), it became clear that a centralized controller-based architecture was a better solution.
- Network functions are virtualized by the controller.
- Data Plane is the architecture implemented within OpenFlow switches.
- SDN provides globalization, while Network Function Virtualization (NFV) is the methodology used.
References
Prof. Dr. Berk CANBERK, Next Generation Wireless Networks, Broadband Communication Research Group
