SD-WAN Architecture: Master concepts and terminology you need to know now

Introduction

In this post we’ll be covering SD-WAN Architecture and how to master the concepts and terminology you need to know. Software-Defined Wide Area Networking (SD-WAN) represents a fundamental shift in how enterprises manage and optimize their network connectivity, offering unprecedented flexibility, security, and performance benefits.

In today’s distributed business environment, traditional WAN architectures struggle to meet the demands of cloud applications, remote work, and digital transformation initiatives. SD-WAN emerges as a strategic solution, providing intelligent routing, enhanced security, and simplified management across complex network environments. Whether you’re planning an SD-WAN deployment, optimizing an existing implementation, or simply staying current with network technology trends, mastering these concepts is essential.

This comprehensive guide breaks down the core components, architectural models, and security features that form the foundation of SD-WAN technology. We’ll explore everything from basic terminology to advanced concepts, helping you build the knowledge needed to make informed decisions about your network infrastructure. Let’s dive into the key elements that make SD-WAN a transformative networking solution.

Concepts and Terminology You Need To Know

Network Architecture

Software Defined WAN (SD-WAN)

A networking architecture that separates the control plane (management and decision making) from the data plane (actual packet forwarding). SD-WAN uses software to intelligently route traffic across the WAN based on current network conditions. This enables centralised control and automated management of multiple connection types. This centralised control provides visibility and control that traditional WAN architectures can’t match.

Underlay Network

The physical transport infrastructure that carries the overlay traffic, made up from one or many of the following types: MPLS (Multi-Protocol Label Switching), Broadband Internet, 4G/5G Cellular and Satellite links. Each of these connection types has its own characteristics in terms of cost, reliability, and performance. SD-WAN can actively monitor and utilise multiple underlay networks simultaneously.

Overlay Network

The overlay network is a virtual network that sits on top of the underlay network. These are created using tunnelling protocols such as IPsec, GRE and VXLAN. This allows for logical separation of traffic regardless of the physical topology. It also enables end-to-end segmentation and policy enforcement. The overlay is transport and provider agnostic making it easy and seamless to build a WAN.

Edge Devices

These are the physical and/or virtual appliances deployed at each site in the SD-WAN network. Their key functions include termination of various underlay network connections, local enforcement of polices, traffic optimisation and Quality of Service (QoS). They also monitor connections and collect metrics.

Edge devices are generally deployed as either purpose built hardware appliances, virtual machines (VM’s) on servers or as cloud instances for connecting to cloud-hosted applications.

SD-WAN Network Architecture Components

SD-WAN network architecture relies on three key components working in harmony: the orchestrator, controllers, and data plane. The orchestrator serves as the central management platform, handling configuration and policy management through a cloud-hosted interface. Controllers manage the routing decisions and policy enforcement, directing traffic flow across the network. The data plane consists of edge devices that handle actual packet forwarding, implementing QoS and security policies at each site. When designing your SD-WAN architecture, consider scalability requirements, management overhead, redundancy needs, and how distributed your organization’s network needs to be. Most enterprises benefit from a cloud-hosted orchestrator for easier management, while controller placement depends on latency requirements and regulatory constraints.

Architectural Models

SD-WAN architectures typically follow three models: hub-and-spoke, full mesh, or hybrid designs. Hub-and-spoke connects branch sites through central locations, offering simplified management but potential bottlenecks at hubs. Full mesh enables direct communication between all sites, providing optimal performance but requiring more resources and complexity to maintain. Hybrid models blend both approaches for balanced efficiency and flexibility. When selecting a model, consider factors like application requirements (especially latency-sensitive ones), available bandwidth costs, IT resource capabilities, and security needs. Most organizations opt for hybrid models, starting with hub-and-spoke and adding direct connections where business needs justify the additional complexity.

Closing

“SD-WAN Architecture: Master concepts and terminology you need to know now” has provided you with a foundational understanding of the core architectural elements that make SD-WAN a powerful networking solution. From the basic building blocks of overlay and underlay networks to the nuances of different architectural models, you now have the knowledge to engage in informed discussions about SD-WAN deployments.

As organizations continue their digital transformation journeys, understanding these architectural concepts becomes increasingly vital. Whether you’re planning a new implementation or optimizing an existing network, this knowledge will help you make strategic decisions that align with your business objectives.

In our upcoming articles, we’ll delve deeper into SD-WAN security features, exploring how SASE and zero-trust models are reshaping network security. We’ll also examine management best practices and optimization techniques that can help you maximize your SD-WAN investment. Stay tuned as we continue to build your expertise in this transformative technology.

Ready to learn more? Don’t miss the next instalment focusing on SD-WAN security fundamentals.