What is SD-WAN? Software Defined Wide Area Networking Explained


As businesses have started adopting cloud-based computing, traditional WAN technology is not always capable of handling the traffic, resulting in unpredictable performance, data security risks, and management complexity. SD-WAN addresses the IT challenges facing cloud-focused businesses, delivering efficiency, reducing costs, and improving resource usage without compromising data privacy.

In this business user guide, we explain SD-WAN, its features, working, benefits, and more.

What is SD-WAN?

A WAN is a connection between multiple LANs across locations. SD-WAN or Software-Defined Wide Area Network is a WAN that uses software to control the management, services, and connection between sites. It is a virtual architecture configured and managed programmatically to be easily adaptable to changing needs.

The SD-WAN implements pre-defined protocols to provide a user-friendly interface to control the features. It also helps the WAN handle huge traffic and even supports gateways, VPNs, firewalls, and other features to increase privacy and security across the network.

Such a WAN can consist of routers and switches and customer equipment, all running some software to handle networking, security, policy, and other management functions, depending on customer and vendor preferences. One of the most impressive features of SD-WANs is managing any combination of transport services from LTE and MPLS to broadband internet.

Using a centralized control function, an SD-WAN securely directs traffic across the network to provide improved application performance and a superior user experience, resulting in better agility and productivity with reduced costs.

How does SD-WAN work?

The primary purpose of an SD-WAN is to enable cloud-first enterprises to provide their customers with a high-quality experience for applications.

Here are some of the characteristics attributed to SD-WANs that should help understand how this technology works.

Centralized Control

The control in this type of network system is centralized. It generally sits on a SaaS application on a cloud platform. Control is detached from the hardware to simplify management and improve services. The central controller passes down protocol-based rules that components follow. This approach eliminates the need to control routers and gateways individually.

Multi-Transport System

The gateways in this type of WAN can have multiple connections with a combination of transports like LTE, broadband internet, MPLS, etc. A VPN is usually established across each WAN connection for additional security. This way, the software-defined WAN proves to be a technology spanning a variety of communication infrastructures.

Dynamic Path Selection

Another outstanding feature of SD-WAN is routing traffic on the appropriate link based on traffic or network conditions.

Packets of data can be automatically routing on a particular link when other links are down.  This feature is also used to balance traffic load across available links.

Dynamic path selection also identifies packets by the user, application, source/destination, and other aspects and selectively sends them on different paths.

Policy-based Management

The dynamic path selection feature of SD-WAN for steering traffic works on the Quality of Service (QoS) policy. This policy determines the priority accorded by the SD-WAN to data packets.

The centralized management console helps implement intentions as policies. All the updated policies are downloaded to gateways and routers in the form of operational rules.

For example, an SD-WAN can have the policy to ensure optimum VoIP performance by assigning priority to their packets and routing them on low-latency paths. The traffic that demands high-level security can be restricted to private connections and exposed to security checks before entering the site. File backups can be sent across a broadband connection to save costs.

Service Chaining

Another feature of SD-WAN is the ability to chain with other network services. It often combines with WAN optimization to improve the performance of the application and network. It may route the traffic from a location across a virtual private network to a cloud security service to achieve the best of security, performance, and cost-saving.

What issues does SD-WAN address?

Management of Complex Networks

One of the most appealing characteristics of SD-WAN is the simplicity of management for complex networks that outweighs the cost-saving features of MPLS.

An increasing dependency on cloud applications and hybrid WANs means the complexity of the network is increasing. Conventional WAN management methods cannot be scaled to meet this complexity.

Individually configuring routers and gateways with command-line interfaces and scripts can be erroneous and inconvenient. Productivity suffers when an expert needs to travel to the site to set up new equipment. Network teams that rely on outdated technologies fail to keep up with the latest business needs.

SD-WAN can be helpful in such scenarios. SD-WAN helps IT teams respond quickly to changing needs of modern businesses and take control of complex networks.

Much of the benefits of SD-WAN stem from the ability to deploy and manage equipment from a central site. A new gateway can be set up at the remote location by a non-specialist, the central controller will automatically take charge of the equipment.

SD-WAN vs MPLS: Cost and Constraints

When establishing WAN connectivity between enterprises, MPLS (Multiprotocol Label Switching) is a valuable service. It guarantees privacy, latency, and bandwidth. However, MPLS is quite expensive and not readily available in many locations, thereby being a less practical method of cloud connectivity across situations.

A broadband internet connection, on the other hand, is more cost-effective and available everywhere. Though the internet is not so reliable, the cost savings make it a preferable option.

Most organizations today use a hybrid WAN that combines these transport services so that critical application traffic is routed via MPLS and other data is sent through the broadband internet.

It is much easier to set up a hybrid WAN with a software-defined network to achieve a balance of performance, reliability, and cost for different types of application traffic.


Unpredictable Network Performance

WAN connectivity often suffers from performance uncertainty as it depends on the internet and other public networks. The path taken by the traffic can differ from one transmission to another between source and destination components – resulting in significant variation in latency.

Sometimes, you can encounter bottlenecks along the path from different factors like time-of-the-day congestion and bandwidth limitation. This problem is widespread on the ‘last mile’ of the network when using the internet without a bandwidth guarantee. IT teams generally consider setting up redundant connections at breakout points to minimize the risks of such bottlenecks.

SD-WAN addresses this issue by monitoring different links and using dynamic path selection to choose the best path for traffic at any moment. It also selects the best connection for the most significant traffic by identifying the application traffic. Low-priority traffic such as backups can be steered down a less reliable connection.

SD-WAN Benefits

Enterprises relying primarily on IT applications for communication between different devices, locations, and users find more significant benefits from SD-WAN deployment. Business benefits can include:


With the ever-increasing pace of business, IT teams roll out new and new services every day to support initiatives. SD-WAN provides the much-needed agility for engineers to respond quickly to new requests and change existing services. With SD-WAN, several tasks that previously took hours or days require only a few minutes.

Another agility you can expect from SD-WAN is real-time traffic management. The gateways keep monitoring the health of various links all the time. Traffic gets routed instantly in case a link gets congested or fails.

Application Performance

With the capability of monitoring links and redirecting the traffic as required, SD-WAN improves the performance and availability of the application to a great extent. It can also adjust the performance of the application on a selective basis. It uses deep packet identification to find what applications are associated with WAN traffic.

Policy-based management means it is easy to determine which applications have a higher priority and what paths the packets should follow. For example, it is possible to implement policies to send business traffic over secure virtual private networks, software updates over internet broadband, and video traffic over high-capacity links.

Another way SD-WAN improves application performance is by making it easy to set up breakout points at locations. By avoiding any traffic backhaul through the central point, you can reduce latency and improve performance for cloud-based applications.

Deployment Speed

SD-WAN makes it extremely easy to set up new equipment or technology at a new office site compared to traditional gateways and routers. After an engineer has designed the management console, the appliance can be shipped to the office and set up by any non-IT person. When turned on, it connects to the controller on the network that configures the equipment and gets it online.


With SD-WAN, it is easy to move less critical traffic to low-cost broadband internet from MPLS links. It uses centralized, policy-based management to adjust traffic on broadband without indulging in individual configurations for gateways and routers.

Another way SD-WAN saves cost is through administration, particularly service and maintenance. Experts don’t need to travel to sites for WAN deployment; they can use centralized management to do everything right from their office.

Today’s dynamic business needs can be easily met using secure, easy to manage, resilient, and agile networks. These networks should be scalable and use programmed controls to deploy applications anywhere within minutes. SD-WAN is a solution to these demands as it provides an affordable service delivery platform with automation and analytics.

SD-WAN Advantages and Benefits

Can small businesses benefit from SD-WAN?

Yes. Whether you are a large corporation with several offices and locations or a small family-owned firm, switching your company’s network to an SD-WAN model has several advantages. These mostly concern the use of cloud-based software, as well as hosted voice and video services.

Cloud-based services and other developing technologies are now available to organizations of all sizes, allowing both small and large businesses to improve their efficiency and production.

These cloud-based applications enable remote access to corporate data and analytics that are centrally kept and updated on a regular basis. Both your staff and your customers will have access to the most up-to-date, correct data for products, services, and account information. SD-WAN can assist in ensuring that these applications function properly.

Next Steps

The advantages of SD-WAN for small organizations are obvious. Any SMB that is still using conventional WAN design should migrate to SD-WAN’s dynamic, secure, cloud-based infrastructure. The shift is expected to improve performance, strengthen security, and increase agility while decreasing operational expenses.

SD-WAN seamlessly adapts to cloud applications. Using zero-touch deployment and single-console control centers, it provides enterprises of all sizes with consistent greater performance, visibility, and centralized control over the whole network.

Finally, SD-WAN is scalable, allowing your network to grow with your company. These dynamic and cost-effective features help you, your employees, and your IT administrators.

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