We were recently called in to consult to a large manufacturer. The company had rolled out 4G/LTE and SD-WAN on their own. But when the company ended up with an LTE bill for $96,000 they turned to us for help.
To better understand what happened, let’s take a look at why 4G/LTE is such a powerful complement to SD-WAN, what went wrong, and what you can do to avoid the problem in your network. This is a summary of a much more in depth piece you can find on our site here.
Why 4G/LTE and SD-WAN?
SD-WAN naturally addresses last-mile problems in many respects far better than MPLS. Good SD-WAN design all but assumes a site will be connected by at least two circuits. With multiple connections, the possibility of a single point of failure is removed, and by using both connections IT never wastes bandwidth. Should one circuit be cut or experience a brownout, SD-WAN appliances will automatically switch traffic to the secondary connection, switching back to the primary connection when available.
At the same time, last-mile service redundancy can be trickier than you might initially expect. Purchasing separate Internet or MPLS circuits might still not guarantee a redundant last mile. By using different types of last-mile technologies, such as fiber and 4G/LTE,you all but force diversity in the physical infrastructure.
What went wrong
As a metered service, 4G/LTE pricing is fundamentally different than other last-mile solutions. The more 4G/LTE bandwidth used, the higher your bill can be. This can be a problem with the wrong SD-WAN solution.
To switch between last-mile circuits, SD-WAN appliances must constantly sample the line. Sampling the line too frequently, consumes 4G/LTE bandwidth, increasing costs. In the case of our customer, their SD-WAN devices set one heartbeat interval for all last-mile networks. The “fat” protocol sampled the line so frequently that over the month the 4G/LTE usage far exceeded plan capacity, increasing costs.
To avoid similar experiences, you need to vet SD-WAN solutions during your selection process. Ask vendors about their 4G/LTE support and specifically around brownout and blackout detection. Determine the rate at which they sample connections and calculate the impact in terms of 4G/LTE costs. We discuss these issue at greater length in the full blog here but you’re always welcome to contact us, if we can help.