What is SD-WAN?

1. Understanding SD-WAN

1.1 What is SD-WAN?

SD-WAN, the acronym for Software-Defined Wide Area Network is a cloud-delivered, highly secured technology that deploys a software-defined networking approach over a wide area network. Such a software-defined approach, by decoupling the network hardware from its control mechanism, simplifies the operations & management of a WAN.

The SD-WAN model is designed to fully support applications hosted in on-premise data centers, public or private clouds and SaaS services, while delivering the highest levels of application performance. The ability to manage multiple connections from MPLS to broadband to LTE and the power to segment and secure the traffic traversing the WAN are the leading edges.


  1. Understanding SD-WAN
  2. Comparison with MPLS
  3. Benefits of SD-WAN
  4. Considerations while adopting SD-WAN:
  5. SD-WAN Challenges

1.2 SD-WAN Overview:

Wide Area Networking has always posed various challenges for organizations with distributed workforces. Fast & reliable application performance, high cost of network circuits, configuration, and management complexities amplify across a WAN. During scaling up of operations, either organically or through M&A, it is quite challenging for the IT teams to deploy the facility quickly, connecting users to business applications.

While the WAN optimization & traffic shaping helps to improve IT abilities to a great extent but all the problems at the network edge are not resolved with it. The dedicated circuits can take months for their deployment and additional staff is required to manage the devices at remote locations. All this is highly cost-prohibitive as well.

The SD-WAN technology abstracts and automates the tasks that used to be manually programmed in WAN, on each device. Such software-defined architecture creates a network overlay, enabling the IT team to configure. Manage, monitor, and secure the WAN aspects, remotely.

By automating, centralizing, and providing more flexibility, SD-WAN results in a more agile environment.

1.3 How SD-WAN technology works?

While the traditional WAN only has the ability to route applications through MPLS, the SD-WAN solution connects the user to any application wherever it resides from the data center to the cloud. Intelligently, SD-WAN assesses the best path meeting the ideal performance needs for a specific application.

Elaboration on following main characteristics defines the SD-WAN working; from a perspective of its evolution from simple WAN:

Application Performance

With the conventional WAN solutions organizations face hardships in delivering high-performance bandwidth for critical applications. But, the SD-WAN cognitively identifies the applications on the very first packet of data-traffic.

As relying on packet routing, traditional WAN lacks the application visibility in-depth, but with software-defined methodology, network teams gain the complete visibility they need about which applications are used the most. This helps in making well-informed, smarter business decisions.

Path Selection

SD-WAN auto-determines the best path for the application to maximize the functionality. Along with the dynamic path selection for traffic to pass through a MPLS connection, broadband connection, and LTE, the self-healing capabilities automatically route traffic to the next best available link in outage of the primary link. Such automated capabilities reduce network complexities and also improves the application performance and user experience.

Zero-touch deployments

With greater control and data plane separations, SD-WAN ensures centralized management and orchestration. Faster deployments with zero touch capabilities at unified management consoles for both network and security features simplify the operations at WAN-Edge.

Orchestration through a single dashboard

Specialized tools and management platforms allow the businesses to establish the automation to ease the deployments and save time & efforts. This also allows them to respond more swiftly to the changing business demands. The centralized management and orchestration with a dedicated platform also enhances the overall efficiency by data analytics & intuitive workflows.

1.4 Types of SD-WAN

There are different deployment models for SD-WAN. For the difference in overlay residence, infrastructure, and device management, various kinds of SD-WAN are as follows.

OTT Services: Over the Top service providers offer SD-WAN as a service using third-party infrastructure for the last mile.

SD-WAN Edge: Edge vendors offer virtual and physical appliances for deployment at the enterprises. All the capabilities for building the virtual overlay reside in that appliance.

Cloud Services: SD-WAN cloud shifts virtual overlay from the edge to the cloud. The cloud services have their backbone and in general, rely on third-party for the last mile.

Carrier Services: In this service, SD-WAN appliances are bundled with a provider’s own last-mile infrastructure.

2. Comparison with MPLS:

2.1 SD-WAN vs. MPLS:

Multiprotocol Label Switching (MPLS) has always been a trusted connectivity option for organizations but its inflexibility and higher costs have been the deterrents. SD-WAN architecture enables the organizations to continue their MPLS circuit with better efficiency and cost-effectiveness by adding alternates like broadband.

MPLS has the advantage of being a private connection offering end-to-end Quality of Service. Also, the service providers deliver a comprehensive service-level agreement than those vendors who offer connectivity over public links.

Technically the MPLS and SD-WAN services are complimentary, but in contrast, they are considered to be competitive.

2.2 Leading Edges of SD-WAN

In terms of the network operation visibility, SD-WAN offers a broad application visibility while the packet routing in case of MPLS limits the visibility.

SD-WAN also enables the MPLS, broadband, and LTE for higher speed, while MPLS offers limited bandwidth and a single point of failure.

SD-WAN also offers easy network scalability and expansion to add secure connectivity with full mesh. While with MPLS, scaling the network up is a complex and lengthy process which sometimes takes even months.

MPLS is an expensive set up to build and maintain, but SD-WAN services greatly reduce TCO

3. Benefits of SD-WAN

3.1 Network Usage and Reliability

SD-WAN uses the most optimum network available every time. It will auto-select between different channels and uses the best medium for a given application. It also connects locations with multiple data-services running in the active-active configuration and allows sessions to move to a new transport in case of blackout without interrupting upper applications.

3.2 Flexibility:

SD-WAN scales the bandwidth up or down at a moment’s notice and has the capabilities to redistribute it for accommodating flash conditions or new applications. This ensures the reception of critical bandwidth for the applications whenever it is required. Moreover, SD-WAN nodes configure themselves and can use 4G/LTE for instant deployment, while you wait for other circuit installations.

3.3 Manageability:

Lower administration costs & better control provides a different level of network visibility that is not available with conventional networks.

3.4 Security:

Encrypted connectivity with SD-WAN secures traffic in transit across any transport.

3.5 Cost-Effectiveness:

The broadband internet performance with SD-WAN is as-good-as MPLS thus in majority of the cases it eliminates the need for costly MPLS networks. There is almost a 90% difference in the cost of MPLS and SD-WAN.

4. Considerations while adopting SD-WAN:

SD-Wan is much like a need of the hour today and an important part of your digital infrastructure. While opting for SD-WAN, following features must be kept in mind to get the best.

4.1 Endpoints Connectivity:

To any application, to any software, and any resource like IaaS or SaaS or the mobile users, make sure that SD-WAN solution connects to every endpoint.

4.2: Encrypted Network:

Traffic over the entire overlay network must be encrypted thoroughly to avoid any threats, and the overlay should be policy-driven.

4.3: Policy-driven Routing:

SD-WAN must include those algorithms that can find out the most optimum path for a specific application, based on real-time statistics and the application- configured policies.

4.4: Application-Based Policies:

The configurable policies must define for the applications, like- failover alternatives, and the maximum & minimum threshold for jitter, latency, and loss.

4.5 Independent Services:

With multiple stations and various data service categories like xDSL, 4G/LTE, fiber, cable, ensure the SD-WAN compatibility with the hybrid deployments.

4.6 Load Balancing:

SD-WAN must have the ability to load balance and manage multiple inbound and outbound traffic requests, making sure that bandwidth will be properly utilized.

4.7 Resilience:

The SD-WAN must support redundancy and failover features. The network core must be full-fledged redundant with the users and must automatically connect to the next Point-of-Presence in the case of any failure.

4.8 Flexible Traffic Management:

The control access and the traffic forwarding towards the WAN connections is a vital step, especially in the case of the limited bandwidth. While adopting for SD-WAN, the support to traffic shaping, rate limiting and the Quality of Service between the user end and the provider’s edge must be ensured.

5. SD-WAN Challenges

Following are the various challenges in SD-WAN deployments.

5.1. Security Concerns:

SD-Wan offers the ability to configure security policies in detail but the right security features and policies must be defined and configured after a thorough assessment.

5.2. Deployment:

Never assume that zero-touch provisioning will be an easy task of simple installation. Extensively examine the provisioning features and routing of traffic and drafting policies.

5.3. Connectivity:

While designing the SD-WAN architecture and getting connectivity, it is prudent to pay attention to the network performance and resilience along with the international links.

5.4 QoS:

Though with SD-WAN, the traffic treatment, path selection, and packet loss detection can be easily assessed but the monitor latency and the jitters, based on the connection types, leading to a better QoS must also be considered