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What is an SDN (Software Defined Network) network?

Software-Defined Network (SDN) is an agile network architecture designed to streamline IT management and centralize control, helping businesses adapt to the dynamic nature of today's applications.

It separates network management from the underlying network infrastructure, allowing administrators to simplify the provisioning of network resources.

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What is an SDN network?

What are the main advantages of an SDN network?

An SDN architecture is built around the need to provide reliable and fast access to business applications. It responds to the dynamic nature of today's applications.

which depend on interactions between servers and the underlying network to provide the right connectivity. As organizations increasingly opt to deliver an assortment of SaaS, web, and cloud applications, traditional network service providers are lagging behind in automation and programmability. In response to this situation, SDN technology was developed to provide organizations with new functionality.

Key advantages of an SDN network:

  1. Increased agility: By separating the control panel, responsible for routing network traffic, from the data panel, which transmits data through routers, SDN enables organizations to gain agility. This scalability is ideal for today's dynamic applications with high bandwidth requirements.
  2. Increased programmability: Without vendor-specific protocols or proprietary software, SDN enables IT to quickly configure, secure, and optimize network resources. Network control is decoupled from the transmission panel, so the network is directly programmable.
  3. Centralized control: With an SDN, engineers and administrators can manage network services using a centralized software management tool, which enables them to respond quickly to ever-changing business constraints.
  4. Reduced complexity: An SDN network greatly reduces the complexity of static networks. By automating network functions and simplifying resource provisioning, organizations can deliver applications very quickly and easily.
  5. Simplified operations: Because it supports automation, SDN alleviates the administrative burden of configuring key features, such as quality of service (QoS) and security.
  6. Better use of network resources: By making the most of virtual resources, organizations that adopt SDN can reduce their operational expenses (OPEX).
  7. Faster time-to-market: SDN enables organizations to take advantage of open APIs and third-party integrations, simplifying application deployment and accelerating time to market.

What does an SDN architecture look like?

While there is no single model of SDN network, this type of network architecture has evolved over time.

One of the first SDN communication protocols was the OpenFlow model, which was essential to the initial development and standardization of SDN. Managed by the Open Networking Foundation (ONF), this approach involves organizations deploying network devices (controllers, routers, and SDN switches) designed specifically to support the OpenFlow protocol. As SDN has evolved, many companies have found this early model too restrictive and have come up with alternative solutions.

This is how network virtualization models appeared, which allowed the creation of virtual networks. These virtual networks can be decoupled from the underlying network hardware and controlled programmatically.

How does SDN work?

In an SDN network, a software application controller manages the network and its activities. Instead of using hardware to support network services, SDN allows network administrators to virtualize the physical network connection.

This network virtualization is made up of three layers (the application layer, the control layer and the infrastructure layer) linked via ascending (Northbound) and descending (Southbound) APIs.

  • The application layer includes a set of network applications and functions, which help improve network performance, simplify IT, and enhance security. Examples: application firewall, Optimization Controllers WAN (Wide Area Network), load balancer, and application delivery controllers (ADC) and authentication. Traditional networks use a special appliance for these functions while an SDN network uses the controller to manage the behaviour of the data panel. The application layer contains programs, which transmit specific network instructions to the SDN controller.

  • The control layer manages policies and traffic flow within the entire network. It consists of the SDN controller, which connects the application layer to the infrastructure layer. This layer processes the requests sent by the application layer through the downlink API, then forwards them to the real network infrastructure through the upstream API. It also returns the information extracted from the infrastructure layer to the application layer to optimize the functionalities.

  • The infrastructure layer is made up of the physical network switches and routers within the data centre. These network devices control important data transmission and processing functions, and they are responsible for collecting critical information, such as consumption and network topology, back to the control layer. 

Key components of an SDN network:


The SDN Controller The SDN

The controller is the application that communicates with network devices and applications within an SDN. At the heart of the network, it connects the application layer and the infrastructure layer and controls the flow of data between the upstream and downstream APIs.

Ascending API (Northbound)

The ascending API (Northbound) enables communications between the control layer and the application layer.


API The Southbound API enables communications between the control layer and the infrastructure layer.

Network Function Virtualization (NFV)

Network Function Virtualization allows hardware functions such as load balancers, firewalls, and routers to be virtualized and brought together in virtual machines. With NFV, organizations don't need to invest in hardware for every network function.

Network and Security Services

These are features that allow business applications to operate efficiently and securely. These include a wide range of virtual network functions, including ADCs, WAN optimization controllers, and firewalls discussed above, as well as security functions, such as intrusion detection and intrusion protection systems. intrusions, and protection against DDoS (distributed denial of service).

Pure SDN Switch

In a pure SDN switch, all of the control functionality of a traditional switch (i.e. the routing protocols that are used to design the retransmission information bases) run within the central controller. The functionality inside the switch is limited exclusively to the data panel.

Hybrid Switch

In a hybrid switch, SDN technologies and traditional switching protocols run simultaneously. This allows the network manager to configure the SDN controller to detect and control specific traffic flows, while traditional distributed network protocols will continue to route the rest of the traffic on the network.

Hybrid Network

A hybrid network is a network in which traditional switches and SDN switches, whether pure SDN switches or hybrid switches operate in the same environment.

How does Citrix help businesses with SDN?

Citrix helps organizations of all sizes adopt SDN with flexible options that allow you to:

  • Simplify the process of optimizing performance for SaaS, cloud, and on-premises applications using advanced application delivery controller solutions
  • Keep your applications and APIs secure with an application security solution delivered as a cloud service
  • Deploy and troubleshoot applications with application management solutions designed to integrate with the SDN controller of your choice
  • Ensure an Always-on network experience with an SD-WAN service designed to connect remote sites and data centres on a global scale.

My name is Duc "JOSEF" Le and I work in Digital Marketing at Mageplaza and BlogAvada. Mageplaza offers a comprehensive collection of over 230 extensions that are designed to work seamlessly with the latest versions of Magento 2 (Adobe Commerce). Meanwhile, BlogAvada is a blog that serves as a platform for sharing information related to websites, mobile apps, e-commerce, digital marketing, and other related topics. I encourage you to visit our websites to learn more about what we have to offer.

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