What is Software-Defined Networking?
Software-Defined Networking (SDN) is an emerging architecture that aims to decouple the network control and forwarding functions. This allows network control to become directly programmable and the underlying infrastructure to be abstracted from applications and network services.
The key characteristics of SDN include:
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Separation of the network control plane from the data plane – Control plane functions like determining optimal paths are separated from the underlying router or switch. This allows for more flexible network management and control.
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Centralized control – Network intelligence is logically centralized in SDN controllers which maintain a global view of the network. These enable easier configuration and management.
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Programmability – SDN controllers expose APIs and interfaces so the network can be programmatically configured to adjust policies and perform traffic steering.
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Abstraction – SDN provides an abstraction between the physical network and how the network is used. This simplifies end-user consumption of services.
SDN provides key benefits such as:
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Flexible network configuration – Network can be easily reconfigured using centralized SDN controllers.
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Improved automation – All changes can be programmed via APIs rather than manual configuration.
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Reduced costs – By automating manual tasks and consolidating network equipment like routers and switches.
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Better traffic management – SDN gives a centralized point of control to manage the entire network traffic.
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Easier deployment of new services – New network capabilities can be deployed without configuring individual devices.
Key SDN Components
The main components of an SDN architecture include:
SDN Controller
The SDN controller is the brain of the network. It maintains a view of the overall network and makes decisions about where traffic is sent. The controller exposes APIs that enable the underlying network infrastructure to be programmed and abstracted. Popular open source SDN controller platforms include OpenDaylight and the Open Network Operating System (ONOS).
Southbound APIs and Protocols
Southbound APIs allow the controller to communicate with the data plane and network devices like switches and routers. Common protocols include:
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OpenFlow – The first standard southbound API for SDN. It allows direct manipulation of the forwarding plane of network devices.
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NETCONF – A network management protocol that provides mechanism for installing, manipulating, and deleting configurations on network devices.
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P4 – A programming language that allows developers to define packet forwarding behavior on switches and routers.
Network Infrastructure
The physical network devices like switches, routers, gateways that ultimately handle network data packets. With SDN, these devices become simpler as control plane logic moves to the centralized controller.
Northbound APIs
Northbound APIs enable higher level applications and business logic to interface with the SDN controller. They abstract away the underlying network infrastructure details.
SDN Use Cases
Some key use cases where SDN delivers value include:
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Data center networking – SDN allows data center networks to be programmed and virtualized more easily. Network provisioning and modification can be automated.
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Network virtualization – SDN enables multiple virtual networks to be created on top of a shared physical network infrastructure. Useful for multi-tenant environments.
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Network automation – SDN automation capabilities improves agility of networks changes through programmability.
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Improved security – The centralized controller provides greater visibility across the network and can help detect anomalies and dynamically respond.
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Traffic engineering – The controller can manipulate traffic flows across the network to utilize capacity better and minimize latency.
Implementing SDN
Some key considerations when implementing SDN include:
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SDN controllers – Selecting the SDN controller platform that aligns to skills and integrates with existing infrastructure.
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Network hardware compatibility – Ensure network devices like switches and routers are OpenFlow or other protocol compliant. May require hardware upgrades.
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Application integration – Exposing services via northbound APIs requires integration work to connect business applications.
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Staff skills – Evaluate if existing network teams have automation and programming skills required for SDN or whether training is required.
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Security implications – Centralized control plane may present security risks that need addressing.
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Migration strategy – Gradually transitioning legacy network infrastructure to SDN vs a forklift upgrade approach.
The Future of SDN
While still evolving, SDN adoption is accelerating as it offers significant benefits in programmability and automation. Gartner predicts that by 2024, 60% of enterprises will implement SDN to improve agility and operational efficiency. As companies embrace digital transformation, SDN is key to providing the network flexibility and automation needed to enable business innovation. The future is bright for this software-defined shift in networking.
