What is software-defined networking?

Software-defined networking (SDN) refers to the physical decoupling of the network control planethat makes routing decisions and forwarding planetransmits data packets through routers. The separation of network control and forwarding functions allows for direct programming of the network control and the abstraction of the underlying infrastructure for applications and network services. The OpenFlow protocolOpenFlow protocol regulates traffic across switches and routers from various vendors. It monitors network traffic and the transmission of packets. It also takes controlled decisions to ensure steady traffic flow. is a fundamental building block for SDN solutions.

Software-defined networking (SDN) is distinct from conventional networks that manage network traffic using specialized hardware (such as switches and routers). Through software, SDN can create and manage virtual networks or traditional hardware. The primary distinction between SDN and traditional networking is that of architecture.

SDN is software-based networking. Compared to conventional networking, SDN is far more flexible because the control plane is software-based. SDN improves security in several different ways. However, since software-defined networks rely on a centralized controller, protecting the controller is essential to upholding the network's security.

Architecture

SDN architecture is divided into three layers, as illustrated below:

SDN architecture

Application layer

Programs on the application layer send specialized network instructions to the SDN controller. Software-defined networks employ the controller to govern data-plane behavior. In contrast, traditional networks use a specific device for these tasks.

Control layer

It controls network traffic and policy implementation. It consists of the SDN controller, which links the infrastructure and application layers. Southbound API and Northbound API are used to process the requirements and send the data packet to the legitimate target, respectively.

Infrastructure layer

The data center's hardware switches and routers are present in the infrastructure layer of the SDN. These network devices are in charge of gathering useful data, controlling critical forwarding operations, offering data processing capabilities, monitoring network traffic stats, and link's state information.

Components

The core components of a software-defined network are defined as follows:

  • The SDN Controller is the application that interacts with networking devices and other applications. It acts as the network's central hub by connecting the application and infrastructure layers and managing the data flow between northbound and southbound APIs. It is involved in monitoring network devices' stats and links. It helps network administrators implement policies and requirements, ultimately resulting in controlled routing decisions. The SDN controller can be a separate new node or any node on the network that works on the master and slave principleThe master node is the one that acts as the centralized node. All the slave nodes request resources from and report about the status of the tasks to the master node..

  • Southbound API makes it feasible to communicate between the control and infrastructure layers. Additionally, this enables the router to recognize the network's topology, determine network flows, and carry out requests that are delivered to it via northbound interfaces.

  • Northbound API allows communications between the control and application layers. The applications demand resources from the network and answer the requirements.

Differences between SDN and traditional networking

The following table lists the differences between SDN and traditional networks. It is clear from these why SDN is preferred among the two.

Attributes

SDN

Traditional networking

Network view

Global centralized view

Localized view

Network management

Easy with the help of SDN controller

Complex because changings must be implemented separately for each device.

Programmable

Yes

No

Maintenance cost

Low

High

Time required for error handling and update

Quick because of SDN controller

Could take months

Security attack detection

Quick and easy

Difficult

Resource utilization

More

Less

Flexibility

More

Less

Benefits

SDN provides the following advantages:

  • Administrators can immediately segregate or create separate zones for devices that need varying security levels to prevent the affected devices from compromising the rest of the network.

  • Instead of manually configuring numerous vendor-specific hardware devices, developers can construct an open-standard software-based controller to govern traffic flow over a network. This results in increased control with greater speed and flexibility.

  • Administrators can centrally configure network services and assign virtual resources to customize the network infrastructure with a software-defined network. This enables network administrators to prioritize applications that demand greater availability and optimize the data flow via the network.

  • SDN controller provides a global view of the entire network, which helps in making controlled routing decisions.

Drawbacks

SDN proves beneficial to an organization in several ways. However, it also has some drawbacks. A few of these are listed below:

  • Being centralized, there could be the possibility of a single point of failure. This means that if the centralized part of the system stops working due to any circumstance, the entire system fails. This potential vulnerability can be avoided by establishing controller redundancy on the network with automatic fail-over. However, it could be expensive to maintain business continuity. This is also no different from introducing additional redundancy to other network components.

  • In terms of scalability, it is not suitable for enterprise networks to manage such an extensive network. However, it can be effectively used for private networks.

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