Modern SD-WAN Architecture Explained: Cloud Gateways, Security, and Multi-Cloud Connectivity

A Deep Dive into SD-WAN Architecture: Your Go-To Guide for Today’s Enterprise Connectivity

As businesses shift to hybrid work models, multi-cloud setups, and more distributed applications, SD-WAN (Software-Defined Wide Area Networking) has become essential for modern connectivity. The diagram shared here showcases a full SD-WAN architecture, highlighting elements like branch locations, mobile users, cloud gateways, cloud security proxies, SaaS applications, IaaS platforms, and private data centers.

This blog breaks down that architecture into straightforward, technically accurate parts—perfect for telecom experts, network engineers, or tech fans looking to grasp how SD-WAN smartly manages and secures traffic in a cloud-first environment.

What Is SD-WAN?

Software-Defined WAN is a solution that’s aware of applications and is centrally managed, replacing conventional MPLS connections with secure overlays that work on broadband, LTE, fiber, and other transport methods.

Key features include:

Dynamic path selection

Optimizing application performance

Centralized control and policy management

Routing optimized for cloud and SaaS

Secure overlays with encryption

Integration with SASE and cloud security services

The diagram illustrates how these components work together in a real enterprise setting.

Breaking Down the SD-WAN Architecture in the Diagram

The graphic shows a comprehensive SD-WAN ecosystem connecting:

Mobile and remote users

Branch offices

Cloud security proxies

Cloud gateways for SD-WAN

SaaS applications like Office 365, Salesforce, Workday

Public Internet services such as Google, Twitter, LinkedIn

IaaS/PaaS platforms like AWS, Azure, Google Cloud

Core data centers of the enterprise

The architecture relies on numerous traffic flows, cloud layers, and control features.

1. SD-WAN Fabric: The Central Transport Layer

At the heart of the architecture is the SD-WAN Fabric, which connects:

Internet links

Private WAN lines

Mobile/backhaul networks

This fabric creates the overlay tunnels that facilitate encrypted and policy-driven traffic.

Main traits of the SD-WAN fabric:

Transport-independent overlays (Internet, LTE, MPLS)

Smart path selection based on real-time performance

Centralized policy enforcement

Application-aware routing that prioritizes essential SaaS services

Three types of endpoints connect to this fabric:

Mobile Users (using the SD-WAN client)

Remote Sites / Branch Offices

Applications and Data Centers

2. SD-WAN Cloud Gateways

The SD-WAN Cloud Gateways appear in the diagram as two crucial nodes found in the cloud edge layer.

These gateways serve as the nearest entry points to the SD-WAN fabric and are strategically located close to major cloud service providers and Internet exchange points (IXPs).

What SD-WAN Cloud Gateways do:

Manage incoming traffic from remote/mobile users

Provide best-path access to SaaS and IaaS platforms

Offload VPN terminations from on-site appliances

Enhance global performance by minimizing latency using proximity routing

They also facilitate connectivity between applications across various cloud workloads in different VPCs or VNets.

3. Cloud Security Proxy: The SASE Component

The diagram highlights a Cloud Security Proxy, which connects mobile users and branch sites, especially for secure internet access.

This reflects the SASE/SSE (Security Service Edge) functions, which include:

Secure Web Gateway (SWG)

Cloud Firewall (FWaaS)

Data Loss Prevention (DLP)

Zero Trust Network Access (ZTNA)

CASB (Cloud Access Security Broker)

The dashed orange line indicates how branch and remote users direct their traffic through this security proxy before reaching public or SaaS endpoints.

4. SD-WAN Controller: The Network’s Brain

Positioned at the top right of the architecture, the SD-WAN Controller interacts with the entire SD-WAN fabric via APIs.

Responsibilities of the Controller:

Zero-touch provisioning for branch devices

Policy creation and distribution

Monitoring (telemetry, analytics, diagnostics)

Automation for routing and security

Centralized authentication for users and devices

In real-world applications, this controller might be cloud-hosted, serving as the “single pane of glass” for network admins.

5. Integration of Mobile and Remote Users

The diagram shows how remote user traffic enters the SD-WAN fabric through SD-WAN clients.

Benefits for Mobile SD-WAN users:

Encrypted connections from anywhere

Optimized access to cloud resources

Consistent adherence to enterprise security policies

Smooth network transitions while roaming

This feature is crucial for hybrid workforces.

Traffic Flow Types Explained

The diagram uses color-coded lines to show how different types of traffic navigate the network.

1. SD-WAN Overlays (Black Lines)

Encrypted tunnels connecting branches, gateways, clouds, and data centers.

2. App-to-App Traffic (Blue Lines)

Direct communication between cloud services or app-to-data-center.

This is vital for both multi-cloud and hybrid-cloud setups.

3. SaaS/Internet Breakout (Solid Orange)

Branches access SaaS or the public internet directly via SD-WAN policies.

4. Traffic to Cloud Security Proxy (Dashed Orange)

Traffic is first scrutinized by a cloud security engine.

5. CSP Direct Connectivity (Purple)

Some cloud resources link directly to SD-WAN gateways or core data centers without going through the public internet.

6. Multi-Cloud Integration

In the architecture, three major IaaS/PaaS providers are highlighted:

Amazon Web Services (AWS)

Microsoft Azure

Google Cloud Platform

SD-WAN gateways facilitate connections with cloud VNets/VPCs, supporting:

Enterprise workloads

Databases

Internal applications

Microservices

The importance of multi-cloud integration:

Ensuring redundancy and failover

Optimizing costs

Enhancing performance

Meeting regulatory compliance

Preventing vendor lock-in

SD-WAN helps extend the corporate WAN into each cloud in a secure and consistent manner.

7. Public Internet and SaaS Optimization

The architecture routes traffic to prominent SaaS platforms like:

Salesforce

Office 365

Workday

Google services

LinkedIn

Twitter

How SD-WAN enhances SaaS performance:

Chooses the quickest exit path

Lowers latency by leveraging cloud gateways

Directs applications based on DSCP or identity

Avoids unnecessary backhauling to corporate data centers

This optimization is critical since SaaS operations often hinge on low latency.

8. Core Data Center Integration

At the bottom right of the diagram, the Core DC connects to the SD-WAN fabric either via app-to-app traffic or direct connections.

The data center remains vital for:

Legacy applications

Internal databases

Private cloud workloads

Enterprise authentication systems

SD-WAN ensures these workloads remain accessible and secure from any branch location, cloud gateway, or mobile user.

Table: SD-WAN Architecture Components and Their Functions

Component Function Benefit SD-WAN Fabric Core overlay transport Performance, reliability SD-WAN Gateway Cloud on-ramp Low latency SaaS/IaaS access Cloud Security Proxy Security inspection SASE/SSE protection SD-WAN Controller Central management Zero-touch, automation Branch/Remote Sites Local networks Unified WAN access Cloud V Nets/VPCs Cloud workloads Hybrid/multi-cloud Core DC Enterprise apps Private connectivity

Wrapping Up

The SD-WAN architecture depicted in the diagram represents the modern enterprise network—distributed, cloud-first, and application-focused. By combining cloud gateways, security proxies, controllers, and smart overlays, SD-WAN offers the performance, reliability, and flexibility necessary for today’s hybrid work environments and multi-cloud deployments.