SD-WAN has gained a large popularity and adoption in the last decade. While it is not a replacement for traditional WAN circuits, it reveals a completely new way on how broadband technologies are implemented and consumed. It also allows to answer a lot of WAN related challenges that have been introduced by the development of cloud applications and the demand for more bandwidth at the edge of the LANs.
What is SD-WAN
Software-defined Wide Area Network (SD-WAN) is a virtual WAN architecture that connects and extends enterprise networks over large geographical areas. It is a software-defined approach to provisioning and managing WAN connectivity that provides flexible networking services and cloud access to businesses and edge locations.
With the SD-WAN architecture, there are now viable solutions to the challenges posed by WAN. The SD-WAN technology provides methods to prioritize critical business traffic and take advantage of internet broadband connections used previously for backup and redundancy to connect directly to multi-cloud resources.
SD-WAN simplifies the management of the wide area network fabric with a controller-first overlay that is independent of MPLS, Ethernet, internet, DSL, or LTE networks. SD-WAN controllers intelligently choose among the available transport mediums to deliver good application performance as defined by IT service level agreements (SLA).
An easy way to think of SD-WAN is to picture it as an overlay. A network on top of another network. An example of a good use case is a bank. Banks may have business apps they prefer to access over leased lines for decreased latency. However, they may also have public cloud applications accessible via secure tunnels to their regional public cloud and web applications that could be routed via Direct Internet Access to alleviate loading the private lines. A 4G or 5G cell service can also be a backup to ensure business continuity.
How SD-WAN Works
SD-WAN uses tunneling technology to separate the physical (Underlay) from the logical (Overlay) network. It implements a centralized controller to manage the entire solution and sets a policy to control traffic paths, service level agreements (SLAs), failovers, and monitoring. The SLAs are written based on application-specific information. Once policies are defined, they are pushed from the centralized controller to each SD-WAN node for a more "hands-off" configuration.
One of the main advantages of the Software-Defined WAN is that it can deploy controllers to the public cloud. It will significantly reduce the CAPEX/OPEX costs and improve the management or control plane's overall availability and redundancy. The control plane is consumed using cloud options such as IaaS (Infrastructure-as-a-Service) or SaaS (Software-as-a-Service). Once the controllers are up and running, a secure connection is established with security protocols such as TLS, which uses TCP transport, and DTLS, which uses UDP transport. But by default, all controllers use the DTLS protocol.
The SD-WAN edge routers follow instructions from the control plane or controller. They are placed at any branch or location edge to route any traffic leaving the facility into its appropriate location or path. This is where the SD-WAN is extremely useful, especially in terms of automation, where a lot of things need to be archived.
Benefits of SD-WAN
SD-WAN is a shift in how a Wide Area Network is deployed and managed. As the name implies, SD-WAN is a software-driven technology with application awareness that is managed from a centralized point within the network. It cuts out expensive routing and reduces hardware costs.
SD-WAN helps optimize the user experience and efficiency for software-as-a-service (SaaS)/ public-cloud applications. It simplifies operations with automation and cloud-based management.
SD-WAN also monitors the performance of WAN connections and manages or steers traffic to maintain high speeds and stay within the SLAs.
Unlike MPLS, SD-WAN comes with no bandwidth penalties. Customers can upgrade easily by adding new links, with no changes necessary to the infrastructure or network. Perhaps the greatest selling point for SD-WAN is the ability to cost-effectively mix and match network links according to content type or priority.
SD-WAN provides security virtualization. Most organizations prefer network architectures that integrate security, policy, and orchestration and SD-WAN security covers those bases by unifying secure connectivity approaches. In the SD-WAN architecture, an organization benefits from end-to-end encryption across the entire network, including the internet. All devices and endpoints in the network can be completely authenticated, due to the scalable key-exchange functionality and software-defined security.
SD-WAN solutions include network analysis tools. It makes it possible to view detailed traffic data for each link and the total aggregate traffic and ascertain whether the overlay or underlay is being used at any time.
Layer 7 data can also be included to categorize and reference traffic to SaaS applications. With SD-WAN any access to websites classified as potentially dangerous can be easily detected and also determine whether the security systems have done their job in intercepting such access.
Other important benefits of SD-WAN include:
Simple configurations: MPLS-based networks require multiple devices per branch office, each requiring manual provisioning. However, because SD-WAN is a virtual network function, it can run with other network functions on a single white box server and scale up processing power based on the edge performance needs at each branch location.
Flexibility in choice: Businesses used to depend on telecommunications providers for high-cost, MPLS-based WAN connections. However, with SD-WAN, businesses can use broadband access/wireless networks in addition to MPLS circuits and choose from a broad range of hardware/software vendors, OEMs, and solution providers to deploy their SD-WANs.
Redundancy built-in: SD-WANs are not dependent on MPLS circuits and can establish virtual private network (VPN) connections over standard broadband access, Wi-Fi, and LTE or 5G. With several options, employees and users have multiple ways to stay connected to their apps and data in the public cloud.
Centralized management: Hub data centers and enterprise IT departments can use control plane software to push new policies and services and set up connections across all SD-WAN branches.
So, given these attendant benefits of SD-WAN, it is not surprising that there has been a meteoric surge in its use. In 2019 and 2020, the global SD-WAN market size were USD 1.4 billion and USD 1.9 billion respectively. It is also projected that by 2025 and 2030, this market size would reach USD 8.4 billion and USD 43.0; at Compound Annual Growth Rates (CAGR) of 38.6% and 34.5% respectively during the forecast periods.