SD-WAN adoption is often pitched as a quick win, but the practical starting point is a business case built on your current WAN economics.
A Nemertes Research-backed approach frames SD-WAN as a way to combine multiple connectivity paths per site and apply centralized rules for traffic distribution—then forces IT to quantify savings and outage impact before committing.
Define “mature” SD-WAN and what it must deliver
In its most mature form, SD-WAN combines the simultaneous use of multiple and diverse communication links at each enterprise site, with advanced management that distributes data traffic across those links.
Those links are controlled by a centralized, rules-based administration system, and the stated system goal is to deliver resilience, performance, simplicity, and cost savings.
Translate architecture into resilience and performance mechanisms
For resilience, the model relies on multiple links with transparent traffic failover during failures, plus traffic-splitting techniques across multiple paths to ensure routing.
For performance, the same design approach depends on traffic prioritization mechanisms and other techniques to steer application behavior over the available paths.
Build the numbers: MPLS cost versus outage and productivity loss
The foundation for an SD-WAN business case should almost always be cost, and the cost analysis should cover both the direct cost of MPLS services and estimates of potential revenue losses that could result from network outages or productivity loss tied to such outages.
Nemertes Research’s SD-WAN cost model suggests deployments can easily reduce current and future WAN bills of large networks by several million dollars, and a studied company reduced WAN spending by switching to Internet connectivity to support newly deployed unified communications and cloud computing applications.
That same scenario was expected to translate into $4.9 million less per year by 2019 with SD-WAN than with its prior MPLS network.
Account for operational and deployment-speed benefits
Cost savings are not limited to a single migration path: SD-WAN can reduce costs by combining lower-cost connectivity options such as business SDSL links or even consumer ADSL or FTTH links with higher-cost options such as MPLS, and it can also come from replacing traditional MPLS WAN links with Internet connections.
Operationally, SD-WAN is positioned as a simplification of WAN management by enabling management of the entire WAN from a centralized console rather than making individual changes across many devices.
On agility, SD-WAN is described as improving service activation time for a branch or the time needed to put a new network site into production, with IT able to provide a wired Internet service within a week or a 4G LTE link within one day—timeframes that should be compared with the weeks or months sometimes required to provision an MPLS link at a new site.