What is software-defined networking (SDN)?

Software-defined networking (SDN) is an agile networking architecture designed to help organizations keep pace with the dynamic nature of today’s applications. It separates network management from the underlying network infrastructure, allowing administrators to dynamically adjust network-wide traffic flow to meet changing needs.

Software-defined networking seeks to reduce the complexity of statically defined networks, automate network functions, speed the deployment of applications and services, and simplify the provisioning and management of network resources.

What are the top benefits of software-defined networking?

There’s a reason IDC estimates that the worldwide data center SDN market will be worth more than $12 billion in 2022. Compared to the advancements in compute and storage virtualization, traditional networking has fallen behind in fully realizing the promise of enterprise cloud computing. The dynamic nature of cloud services requires a new level of flexibility and scalability, which goes beyond the capabilities of today’s data center networks.

Transitioning to software-defined networking (SDN) incorporates programmability and agility into your network, enabling it to keep pace with business demands.

A software-defined network allows you to:

  • Support the dynamic movement, replication, and allocation of virtual resources
  • Ease the administrative burden of the configuration and provisioning of functionality such as QoS and security
  • More easily deploy and scale network functionality
  • Perform traffic engineering with an end-to-end view of the network

  • Better utilize network resources
  • Reduce OPEX
  • Have network functionality evolve more rapidly based on a software development lifecycle
  • Enable applications to dynamically request services from the network
  • Implement more effective security functionality
  • Reduce complexity

How does SDN work?

A software-defined network is made up of three layers — the application layer, the control layer and the infrastructure layer — connected through northbound and southbound APIs.

The application layer includes applications and network functions, like firewalls and load balancing. Traditional networks use a specialized appliance for these functions, but a software-defined network uses the controller to manage data plane behavior. The control layer manages policies and the flow of traffic throughout the network. And the infrastructure layer contains the network’s physical switches.

Here’s a breakdown of a software-defined network’s key components:

Business applications

This refers to applications that are directly consumable by end users. Possibilities include video conferencing, supply chain management, and customer relationship management.

Network & security services

This refers to functionality that enables business applications to perform efficiently and securely. Possibilities include a wide range of L4-L7 functionality including ADCs, WOCs, and security capabilities such as firewalls, IDS/IPS and DDoS protection.

Pure SDN switch

In a pure SDN switch, all of the control functions of a traditional switch (such as routing protocols that are used to build forwarding information bases) are run in the central controller. The functionality in the switch is restricted entirely to the data plane.

Hybrid switch

In a hybrid switch, SDN technologies and traditional switching protocols run simultaneously. A network manager can configure the SDN controller to discover and control certain traffic flows while traditional, distributed networking protocols continue to direct the rest of the traffic on the network.

Hybrid network

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

Northbound API

The northbound API enables communications between the control layer and the business application layer. There is currently not a standards-based northbound API.

Southbound API

The southbound API enables communications between the control and infrastructure layers. Protocols that can enable this communication include OpenFlow, the extensible messaging and presence protocol (XMPP), and the network configuration protocol.

How does Citrix help?

Citrix ADC can help you easily transform your infrastructure to a software-defined network with the highest security, performance, and reliability by:

  • Combining the flexibility of virtualization with the resiliency, reliability, and performance of purpose-built network appliances
  • Unifying L4-7 network services into an application control layer, and making L2-3 architectures completely app-driven
  • Providing policy-based automation administered through a single console, for more efficiency, higher performance, and lower OPEX costs

Additional resources