1. Vendor selection

The first challenge associated with SD-WAN is vendor selection. Most IT decision-makers will begin their SD-WAN investigation with research into the leading vendors. This first step is challenging due to the prolific amount of marketing within the SD-WAN product space. IT teams are overwhelmed with marketing data points that suggest each product can offer digital transformation across WAN services.

Within the last few years, WAN has evolved to encompass technologies, such as Secure Access Service Edge (SASE), integration with major cloud providers, and numerous features to help with application performance and diversity. While security, cloud and new features enable users to work securely from wherever they're located, IT teams need to analyze their user workflows to understand how each vendor is best positioned to deliver its services.

In response to this challenge, IT teams can document the business application flows that currently exist and how the business intends to work over the next decade. While creating this report, teams must pay attention to how users can be more productive by using SD-WAN features.

When making technology decisions, IT teams are often constrained by their existing commitments and network complexity. For example, security vendor contracts don't often terminate at the same time as WAN services. In this scenario, teams should consider vendors that offer good integration with third-party security services. In many ways, existing commitments represent a challenge because vendors are consolidating features into one offering.

2. Underlay provisioning

The shift from private WAN technology, such as MPLS, to the internet as the default connectivity option for SD-WAN makes sense. Almost all businesses are adopting a public cloud-first strategy across SaaS, IaaS and PaaS. The challenge related to SD-WAN revolves around which underlay service providers are best suited to a company's locations -- and whether to use a single IP backbone or multi-ISP strategy.

A single IP backbone makes sense for large, global enterprises, as traffic remains within one autonomous system, creating more predictable latency and jitter across application performance. Conversely, national networks aren't so concerned with round-trip delay, so they may consider a multi-ISP strategy based on individual postal codes.

Teams should consider more than network performance, however. Traditional MPLS network operations centers are known for their focus and troubleshooting ability, providing end-to-end management of both the WAN edge and circuit. Generally, ISPs aren't as focused, which means the onus is on the vendor to troubleshoot and manage connectivity issues. Depending on an IT team's management choice -- adopting DIY SD-WAN versus managed SD-WAN -- it is essential for them to understand how prospective vendors will provide a service-level agreement to monitor and troubleshoot connectivity.

3. Cloud connectivity

In almost all SD-WAN vendor selection projects, IT teams require connection to AWS, Microsoft Azure or Google Cloud Platform. SD-WAN vendors will generally fall into the following three categories regarding their capability to access cloud services:

1. Native cloud access is built into the vendor's architecture and uses cloud backbone infrastructure to connect branch office sites.
2. Vendors deliver their SD-WAN appliances into the cloud environments with public gateways or private backbones.
3. Vendors make it the customer's responsibility to deploy appliances within its local cloud data center.

The first option describes SD-WAN vendors that are adopting the cloud as their global backbone. Deploying cloud gateway architecture isn't widespread yet but is a sensible option because connecting to the local cloud data center is the ultimate destination of user traffic.

The second option provides some flexibility regarding the vendors' go-to-market features, including private backbones or public gateways, which route traffic more efficiently compared to the internet.

Cost reduction is often not quantified in bottom-line savings and requires consideration of the overall benefit to the business.

Finally, the third option provides access to cloud vendors but in a more ad hoc, simplified architecture.

4. Cost reduction

Reducing costs is one of the main drivers and marketing statements associated with SD-WAN. But cost reduction is often not quantified in bottom-line savings and requires consideration of the overall benefit to the business. For example, adopting SD-WAN with SASE enables more efficient working practices. While empowering users to access applications efficiently doesn't appear as a line item on the budget, the overall effect on the business can be huge.

Another standard way to reduce costs is by procuring local site-by-site internet underlay from the lowest-cost service provider. When comparing like-for-like pricing versus MPLS circuits, businesses are saving significantly.

Feature consolidation also represents significant cost savings as IT teams consider vendors that offer appliances with SD-WAN, SASE and cloud vendor access built into their platform. With consolidation, SD-WAN is simpler to manage and use, which positively affects IT departments as they require fewer resources to manage the system.

5. Management

SD-WAN is helping to blur the lines between DIY, co-managed and fully managed SD-WAN. Enterprises don't have to choose their management level in a traditional, static way.

When a provider doesn't own the complete technology stack, it must bring in additional expertise to deliver the system. This is the traditional way of delivering WAN offerings: build a capability by piecing together the platform. This typically results in slow processes as systems between each technology stack often don't work well together.

Vendors that own their complete technology stack can help customers manage their WANs depending on requirements for any given situation. By keeping control of the technology, vendors are well positioned to deal with any requirement across all levels of managed services. If IT teams want to manage changes, SD-WAN management interfaces facilitate this. If teams require a little help, a vendor can assist as it understands the different aspects of the delivered offering.

In contrast, service providers offer their take on SD-WAN by bringing together underlay and overlay with multiple vendor options. The platform is built across multiple vendors, which can result in a less agile, more time-consuming process. If enterprises don't require flexibility across managed services, the managed service provider route is viable.