What Is SD-WAN And Why Are Enterprises Adopting It?

For enterprise IT, wide-area networking (WAN) has been a cornerstone consideration since organizations were first required to connect locations across great distances. 

The answer to that challenge was simple, if complicated and expensive, for decades:

• Dedicated Circuits
• Non-Reconfigurable Topologies 
• Heavy Reliance On Carrier-Managed Infrastructure 

Enterprise technology needs have evolved, and so has the architecture connecting them. 

Software-defined wide area networking has quickly become the foremost answer to that change, gaining traction across organizations of all sizes and industries at an even faster pace.

These four pieces of knowledge- what SD-WAN is, the challenge it solves, and why enterprises are adopting it- serve as an important backdrop to any organization examining its network road map.

The Legacy WAN Problem

The traditional enterprise-wide area networks were created for another time. 

Back then, applications resided in a data center, all users worked from fixed office locations, and the network mostly served the single role of moving traffic between branch offices and headquarters. 

The contract-based MPLS circuits served this perfectly. 

They provided consistent performance, ensured quality of service for latency-sensitive workloads, and offered an isolated, private environment (not the public internet).

That model carried high costs. 

Compared to commodity broadband, MPLS bandwidth is an expensive alternative, especially for intercity and international connections. 

Contracts were designed with multi-year terms and very little room for scale or changes to commitments. 

Before we could deploy new sites, we had to engage the carriers who would provide them, with varying contracting timescales. 

Any change in routing or policy requires manual, per-device configuration, which puts significant pressure on the engineering teams supporting the network.

Enter cloud computing, which brought these constraints under direct stress. 

The traditional hub-and-spoke WAN model became a roadblock as enterprise applications moved from centralized data centers to public cloud platforms and software-as-a-service environments. 

What Is SD-WAN?

SD-WAN is a software-defined network technology for wide-area connectivity. 

Specifically, this objective is achieved when an SD-WAN deployment aggregates multiple transport connections.

These can be MPLS, broadband internet, dedicated internet access, LTE, 5G, or any combination thereof, into a single managed resource. 

Traffic is dynamically routed across these links based on real-time link performance measurements, specific application needs, and policies defined centrally by network managers and applied uniformly across all sites.

What is SD-WAN and how it works helps explain why the technology has become so widely adopted. 

Its popularity stems from the combination of transport flexibility, centralized control, and application-aware routing. 

Rather than committing all traffic to a single expensive private circuit and managing each device independently, organizations can direct traffic over the most appropriate and cost-effective transport path while managing the entire WAN through a single centralized interface. 

Factors Driving Enterprises To Adopt SD-WAN

The trend towards SD-WAN represents an intersection of pressures that were never part of the design parameters for legacy WAN architectures.

1. Adoption Of Cloud And SaaS

The largest driver is the adoption of Cloud and SaaS. 

As enterprise workloads and applications have migrated to cloud environments, the network must provide optimized traffic routing to those destinations.

Cloud-bound traffic can bypass the corporate backbone via an SD-WAN, enabling direct internet breakout at branch locations. 

This not only enhances application performance but also alleviates the burden on central infrastructure.

Moreover, this avoids the latency hit that backhauling inflicts on cloud consumers.

2. Cost Reduction: A Key Consideration

While cost reduction is crucial, it’s not always the only factor. 

There can be a considerable price gap between MPLS circuits and commodity broadband connections; 

SD-WAN allows organizations to replace some of that MPLS spend with lower-cost internet transport.

Moreover, it happens without the performance guarantees required for mission-critical applications. Also, the economics vary dramatically by 

• Geography
• Contract Structure
• Traffic Profile

But transport-related cost savings are often a substantial part of the SD-WAN business case.

3. Agility And Operational Efficiency

The third major driver for enterprise adoption is the need for agility and operational efficiency. 

Traditional WAN management often requires engineering effort at all sites and close coordination with carrier teams for any changes. 

Typically, a less professional cadre of vendors manages this infrastructure. 

SD-WAN enables zero-touch provisioning, in which appliances are preconfigured within the branch topology.

Also, they automatically connect to the SD-WAN centralized administration layer.

Therefore, this eliminates the need for on-site technical expertise. 

Policy changes can be defined once and rolled out to every site within minutes, rather than days or weeks.

4. Broad Industry Relevance

The coverage of SD-WAN networking shows how different factors affect various industries and organization sizes. 

Retail chains need standardized connectivity across many locations. 

Healthcare organizations require reliable access to clinical applications in accordance with established policies. 

Financial services firms deal with operations spread out around the world.

Application-Aware Routing And Policy Control

Application awareness is one of the key capabilities that sets SD-WAN apart from traditional WAN management. 

Instead of applying a one-size-fits-all approach to traffic, SD-WAN platforms continuously assess application behavior and link performance.

Then, they steer specific application types toward the transport path that best meets their needs.

For example, a video conferencing application with low latency and minimal packet loss can be steered along the most stable available path. 

Whereas general web traffic and non-time-critical data transfers may follow a cheaper broadband path. 

But transaction-processing systems that require performance guarantees may keep dedicated circuit connectivity. 

These steering decisions are made in real time at a measured set of conditions and according to policies that administrators define at the central management layer, not on individual devices.

With access to this level of granular control, organizations can easily achieve real cost savings. 

For this, they just need to direct traffic to lower-cost transport options. 

At the same time, they must ensure that performance-sensitive applications receive the service-level experience they require. 

It also gives insight into application performance across the WAN, where traditional router-based architectures are usually blind.

Security Integration In SD-WAN

The shift to SD-WAN in network architecture represents a change in the security posture an organization needs to adopt. 

If branch offices connect directly to the Internet rather than sending all traffic back through a central data center for security inspection, security controls will need to be placed as close to the traffic as possible.

This is why many of today’s SD-WAN platforms include security functions at the WAN edge. 

Inter-site traffic is protected within encrypted overlay tunnels, independent of the underlying transport. 

SD-WAN appliances at each location may incorporate stateful firewalls, intrusion prevention capabilities, and application filtering. 

Therefore, you must ensure you integrate with cloud-delivered security services.

Once you do so, the solution consistently inspects internet-bound traffic from branch offices.

Furthermore, it does not backhaul it through a central inspection point, which would incur latency.

The convergence of networking and security at the SD-WAN edge is part of why this architecture is better suited to distributed enterprises.

It would be operationally prohibitive to deploy and manage separate security appliances across tens or hundreds of locations.

What Is SD-WAN Practical Adoption Patterns?

Organizations typically adopt SD-WAN through a phased approach rather than an immediate wholesale replacement of existing infrastructure. 

The experience documented in enterprise WAN migration case coverage illustrates a certain pattern.

Firstly, the organizations begin by identifying sites or traffic types where SD-WAN benefits are most immediate.

Then they continue piloting the deployment and validating performance and operational improvements.

Finally, they expand across their estate as confidence in the platform grows.

This supports carrier contract terms and service cutovers.

Moreover, it extends the SD-WAN management layer to the internal team without requiring ownership of the whole network. 

It also enables network teams to understand which classes of traffic are appropriate for Internet transport in their environment.

In addition, it clarifies which applications truly require the performance characteristics of retained MPLS circuits.

Also, it is balanced between private and public connectivity to align with: 

• Corporate Performance Requirements
• Geographic Scale
• Economic Goals

The outcome for many enterprises is a hybrid architecture in which an SD-WAN serves as the management layer across heterogeneous transport types.