This concept is similar to how software-defined networking implements virtualization technology to improve data center management and operation.
[3] The need for strict control, security and quality of service (QOS) meant that multinational corporations were very conservative in leasing and operating their WANs.
National regulations restricted the companies that could provide local service in each country, and complex arrangements were necessary to establish truly global networks.
[4] Over the next decade, increasing computing power made it possible to create software-based appliances that were able to analyze traffic and make informed decisions without delays, making it possible to create large-scale overlay networks over the public Internet that could replicate all the functionality of legacy WANs, at a fraction of the cost.
[7] WANs allow companies to extend their computer networks over large distances, connecting remote branch offices to data centers and to each other, and delivering applications and services required to perform business functions.
Due to the physical constraints imposed by the propagation time over large distances, and the need to integrate multiple service providers to cover global geographies (often crossing nation boundaries), WANs face important operational challenges, including network congestion, packet delay variation,[8] packet loss,[9] and even service outages.
[6] By enhancing or even replacing traditional branch routers with virtualization appliances that can control application-level policies and offer a network overlay, less expensive consumer-grade Internet links can act more like a dedicated circuit.
[5] The SD-WAN edge is a physical or virtual network function that is placed at an organization's branch/regional/central office site, data center, and in public or private cloud platforms.
[20] SD-WANs can incorporate artificial intelligence for IT operations (AIOps) for continuous troubleshooting and fixes to network issues.
[21] Most SD-WAN products are available as pre-configured appliances, placed at the network edge in data centers, branch offices and other remote locations.
[13] As with network equipment in general, GUIs may be preferred to command line interface (CLI) methods of configuration and control.
[1] With a global view of network status, a controller that manages SD-WAN can perform careful and adaptive traffic engineering by assigning new transfer requests according to current usage of resources (links).
In December 2021, Gartner research firm estimated that by 2025, 50% of SD-WAN purchases will be part of a single vendor SASE offering.
The goal of each is to accelerate application delivery between branch offices and data centers, but SD-WAN technology focuses additionally on cost savings and efficiency, specifically by allowing lower cost network links to perform the work of more expensive leased lines, whereas WAN Optimization focuses squarely on improving packet delivery.
An SD-WAN utilizing virtualization techniques assisted with WAN Optimization traffic control allows network bandwidth to dynamically grow or shrink as needed.
[32] SD-WANs can work as an overlay to simplify the management of existing WAN edge routers, by lowering dependence on routing protocols.
A hybrid WAN consists of different connection types, and may have a software defined network (SDN) component, but doesn't have to.
As a result, cloud-based SD-WAN can replace MPLS, enabling organizations to release resources once tied to WAN investments and create new capabilities.
Given the breadth of options available in relation to both software and hardware SD-WAN control solutions, it's imperative they be tested and validated under real-world conditions within a lab setting prior to deployment.