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SD-WAN vs. SASE: Where One Ends and the Other Begins

4 min. read
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The difference between SD-WAN and SASE is that SD-WAN is a networking technology that optimizes wide-area connectivity, while SASE is a framework that converges SD-WAN with cloud-delivered security.

SD-WAN focuses on routing traffic across multiple links to improve performance and efficiency. SASE extends this by unifying connectivity with security functions for distributed users and applications.

 

What is SD-WAN?

Software-defined wide area networking, or SD-WAN, is a networking technology that changes how organizations connect their branch offices, data centers, and cloud services. Instead of depending on a single private line such as MPLS, it can use multiple transport types at once. That includes broadband internet, LTE, and other available connections.

Diagram labeled 'SD-WAN architecture' showing six branch office icons, three on each side, connected to a central data center box at the bottom. The branches and data center also connect upward to a box labeled 'Internet' that contains cloud service logos including AWS, Azure, Google Cloud, Dropbox, Salesforce, and Workday. Green lines represent MPLS, purple lines represent cellular, and blue lines represent broadband, all shown in the key at the bottom.

The purpose is simple. Improve the performance, efficiency, and flexibility of the wide area network.

Here's why it matters:

Traditional WAN architectures were rigid and tied to expensive private circuits.

Diagram titled 'SD-WAN control plane and data plane' with two labeled sections. On the left under 'Data plane' are four stacked boxes labeled Cloud, DC, Campus, and Branch, each with a blue router icon. These connect through edge routers to three central ovals labeled MPLS, Internet, and 4G/5G. Lines extend from these ovals through green icons labeled 'Smart controllers' to three orange boxes on the right under 'Control plane' labeled Orchestration, Analytics, and Automation.

But SD-WAN separates the control and data planes. And that allows policies to steer traffic across the best available path in real time. Path selection is based on application requirements and business rules. Not just static routing.

Diagram titled 'SD-WAN control plane and data plane' with two labeled sections. On the left under 'Data plane' are four stacked boxes labeled Cloud, DC, Campus, and Branch, each with a blue router icon. These connect through edge routers to three central ovals labeled MPLS, Internet, and 4G/5G. Lines extend from these ovals through green icons labeled 'Smart controllers' to three orange boxes on the right under 'Control plane' labeled Orchestration, Analytics, and Automation.

In practice, that means the network can automatically shift traffic if a link becomes congested or fails. Applications like voice or video can be prioritized to maintain quality, while less sensitive traffic can be sent over cheaper links.

The diagram titled 'SD-WAN dynamic path selection and traffic steering' shows a branch office connected to various network interfaces. The branch office connects to two virtual interfaces: the VPN virtual interface (IPSec interfaces) depicted in orange and the DIA virtual interface (Ethernet interfaces) depicted in blue. SD-WAN traffic steering includes session load distribution, path quality profile, and traffic distribution profile. Path quality is assessed based on latency, jitter, and packet loss, with a top-down priority for traffic distribution. The VPN interface leads to a private network connecting to headquarters, while the DIA interface connects to the public internet, indicating connections to Internet/SaaS services. Application thresholds are shown at the top left, linking to the branch office through the SD-WAN traffic steering components.

Essentially, SD-WAN is about optimizing WAN connectivity. It replaces the limitations of legacy routing with centralized orchestration, dynamic path selection, and transport independence. Which means the network becomes more resilient, adaptive, and cost-efficient without changing how users or applications interact with it.

| Further reading:

 

What is SASE?

Secure access service edge, or SASE, is a framework that merges networking and security into a single cloud-delivered model. Instead of relying on separate hardware appliances, it provides both connectivity and protection through distributed points of presence.

The goal is straightforward. Secure and connect users, applications, and data–no matter where they're located.

Here's how it works:

SASE brings together networking and security into a single framework.

SASE architecture diagram laid out to show how it integrates different components and locations. On the left, labeled 'Your users' and 'Traffic sources,' are icons for Mobile/Computer, Branch/Retail, and Home, representing various user environments. The central part of the diagram lists components of 'SSE' (Secure Service Edge) including FWaaS (Firewall as a Service), SWG (Secure Web Gateway), CASB (Cloud Access Security Broker), and ZTNA (Zero Trust Network Access). To the right, labeled 'Your data' and 'Traffic destinations,' are icons for HQ/Data Center, SaaS applications, and Public Cloud, indicating where the data resides and is managed. At the top of the central section, 'SSE' is linked with 'A' representing the network access, which includes SD-WAN (Software-Defined Wide Area Network) and Internet Global Networks, collectively underlining the comprehensive network and security coverage SASE provides across varied locations and data pathways.

SD-WAN is the networking foundation, which–as explained–manages connectivity across different links and locations. Security functions such as firewall as a service (FWaaS), secure web gateway (SWG), cloud access security broker (CASB), and zero trust network access (ZTNA) are integrated alongside it.

Together, these capabilities let organizations apply consistent policies and enforce access across cloud, branch, and remote environments.

It's important to note that SASE isn't just a collection of tools. It's an actual architectural approach that shifts networking and security to the cloud. And that shift is what allows organizations to scale, reduce complexity, and deliver a unified experience to users working from anywhere.

In short: SASE equals SD-WAN plus a cloud-based security stack. It's the model enterprises are adopting to replace fragmented legacy systems with a converged way to connect and protect.

 

How are SD-WAN and SASE related?

SD-WAN and SASE aren't separate technologies competing with one another. They're connected. And that's because SD-WAN is one of the essential components inside a SASE framework, as discussed.

Let's break this down.

Again, SD-WAN was designed to solve wide area networking challenges. So it gave organizations the ability to move away from rigid private circuits and route traffic dynamically across multiple connections. And that definitely made networks more flexible and cost-efficient.

But what it didn't do was solve the security problem.

For example(s):

Architecture diagram illustrating the security risks associated with direct internet access at branch locations. It features a branch connected to an SD-WAN router, which is shown in the center. The SD-WAN router connects to a data center at HQ and branches off to the Internet. A switch and firewall are depicted under the branch, indicating additional network components. To the right, 'Attackers' are illustrated as a potential threat, emphasizing the exposure of network traffic to security risks. The title above the diagram notes that this direct access introduces vulnerabilities to the network.
Diagram illustrating the challenges of monitoring in an SD-WAN environment due to dynamic path selection. It shows a branch connected to an SD-WAN fabric, represented in the center. An arrow points to a label indicating 'Blindspot internet traffic,' which signifies unmonitored traffic flowing to the Internet. To the left, an access control list is depicted, accompanied by a note on 'Improper configuration on access control list,' highlighting a potential issue. On the right, HQ is illustrated as a connection point. The title at the bottom notes that dynamic path selection complicates the monitoring process, resulting in blind spots.

So traffic still had to be secured by separate tools and appliances.

And that's where SASE came in. It built on SD-WAN's networking foundation and added the missing security services–all the functions we covered previously (SWG, CASB, FWaaS, and ZTNA). They all converge with SD-WAN under a single cloud-delivered model.

Think of it as an evolution path:

  • Legacy WAN was built on MPLS and fixed architectures.
  • SD-WAN introduced transport independence and centralized control.
  • SASE extends that progress by converging networking and security together in the cloud.

Remember:

SASE still depends on SD-WAN for connectivity. The networking layer provides the basis for applying global security policies and ensuring reliable access. Without SD-WAN's traffic steering and link optimization, SASE wouldn't be able to deliver consistent performance for distributed users and applications.

The bottom line is this. SD-WAN is the transport fabric. SASE is the broader framework that uses that fabric to connect and secure everything everywhere. So one is embedded inside the other.

| Further reading:

 

Does SASE replace SD-WAN?

It's a common misconception that adopting SASE means getting rid of SD-WAN. But that isn't the case.

This view often comes from how SASE is described as the “next evolution” of SD-WAN, which can make it sound like a direct replacement. Confusion also comes from procurement discussions, where buyers are often encouraged to consider SASE platforms instead of separate SD-WAN deployments.

So what does change?

The scope.

SD-WAN focuses on networking. As mentioned, it makes the WAN more efficient. But SASE takes that same networking base and adds the security functions organizations need today.

So SASE doesn't replace SD-WAN. It extends it.

Architecturally, this is how SASE integrates SD-WAN alongside its security layers:

Organizations still deploy SD-WAN. But it comes as part of a larger cloud-delivered framework that unifies networking and security in one architecture.

To put it simply, SASE builds on SD-WAN to give organizations integrated security and connectivity in the cloud era.

| Further reading: SD-WAN vs. SASE vs. SSE: What Are the Differences?

 

When should you use SD-WAN vs. SASE?

The choice between SD-WAN and SASE depends on your environment and priorities. It's not really a matter of one versus the other. It's about what your organization needs now, and what it will need later.

Architecture diagram titled 'When to use SD-WAN vs. SASE'. A central box on the left reads 'What's the priority?'. Three branching arrows point right. The top branch reads 'Need WAN modernization or MPLS offload?' with a label 'WAN performance, transport flexibility, centralized control' leading to a blue box labeled 'SD-WAN'. The middle branch reads 'Need secure access for distributed/cloud users?' with a label 'Networking + integrated security' leading to a teal box labeled 'SASE'. The bottom branch reads 'Already on SD-WAN but expanding security needs?' with a label 'Phased path toward convergence' leading to a dark gray box labeled 'Extend into SASE'.

Start with SD-WAN when the main challenge is modernizing the wide area network.

For example, if you're trying to offload expensive MPLS connections or improve performance between branch offices and data centers. SD-WAN can deliver better routing, transport flexibility, and centralized control without requiring a major architectural change.

On the other hand, SASE makes more sense when networking and security need to come together.

Distributed workforces, cloud adoption, and a push toward Zero Trust are the drivers. Organizations that want consistent policy enforcement across users, applications, and devices will find that SASE's cloud-delivered model addresses gaps that SD-WAN alone cannot.

And don't forget: this isn't an all-or-nothing decision.

Many organizations deploy SD-WAN first, then extend into SASE as requirements evolve. Hardware refresh cycles, existing vendor contracts, and team structures often dictate a phased path. And that means SD-WAN may be a starting point, while SASE is the eventual destination.

To sum up: use SD-WAN when the priority is WAN performance and cost optimization. Use SASE when the priority is securing access everywhere. And recognize that most enterprises will move through both stages on the way to a fully converged model.

| Further reading:

 

What are the main differences between SD-WAN and SASE?

Let's get into the nuts and bolts of how SD-WAN and SASE diverge in terms of scope.

Both improve connectivity, but they were designed to solve different problems. The table below breaks down how:

Comparison: SD-WAN vs. SASE
Dimension SD-WAN SASE
Core focus Application-aware WAN connectivity and optimization Unified framework for secure connectivity everywhere
Key components SD-WAN edge devices, controllers, policies, and overlays SD-WAN + security services (FWaaS, SWG, CASB, ZTNA, etc.)
Security coverage Limited to encryption and basic segmentation Broad, integrated security stack enforcing Zero Trust
Deployment model Hardware or virtual appliances at sites, managed centrally Cloud-delivered model using distributed points of presence
Primary use cases MPLS offload, branch-to-branch and branch-to-cloud optimization Secure access for hybrid work, cloud adoption, and global policy enforcement
User scope Branch offices and data centers Users, devices, and applications anywhere

It can't be said enough: the two aren't competing choices. SD-WAN provides the transport layer that SASE builds on. And that makes it the logical starting point for many organizations– and a permanent part of any SASE deployment.

DIG DEEPER INTO SASE
Want to see how SASE builds on SD-WAN in practice? Secure Access Service Edge (SASE) For Dummies, 3rd Edition breaks down the architecture, security layers, and adoption paths with real-world context.

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SD-WAN vs. SASE FAQs

Yes. SASE inherently integrates SD-WAN's capabilities for optimized network traffic with cloud-native security functions. Therefore, removing SD-WAN from the equation would strip SASE of its foundational networking component, rendering it incomplete.
No. You cannot have SASE without SD-WAN. SASE's framework fundamentally relies on SD-WAN's network optimization combined with cloud-native security features.
No. SASE is not the same as SD-WAN. While SD-WAN focuses on optimizing network traffic and connectivity, SASE combines these capabilities with cloud-native security services.
No. SD-WAN remains essential for WAN optimization and is a foundational component of SASE. While adoption is shifting toward SASE platforms, SD-WAN itself is not obsolete—it underpins modern secure connectivity.
Organizations typically extend from SD-WAN to SASE when cloud adoption, hybrid work, and Zero Trust priorities outpace what SD-WAN alone can provide. Transitions often align with hardware refresh cycles, vendor contract renewals, or broader security modernization initiatives.
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