Keeping it Simple. The 4 basic flavors of SD-WAN explained

The market is moving away from VPN and MPLS rapidly towards SD-WAN. The major hurdle for most customers is understanding which SD-WAN route to take. VPN or IPVPN is easy to understand. It is protocol based and creates a private tunnel using the same protocol regardless of which carrier or carriers you use. MPLS is the same way. It is easy to understand. It is Layer 3 private network using a standard protocol regardless of which carrier you select.

SD-WAN is nothing like that. There is no standard definition or protocol to rely on. There are dozens of different ways and counting that providers come to market and call whatever they are doing SD-WAN. SDN stands for Software Defined Networking and started out as a data center term. SDN is a concept not a product. It literally means Networking defined by the Software. SD-WAN is both a concept and a product you can buy but it is not using industry standard protocols like IPVPN or MPLS. It is SDN as applied to WAN (Wide Area Network) connections. Most people at this point think of SD-WAN as 2 or more data connections that are optimized to act as 1 connection in a way that is faster and more reliable than either one on its own using a magic SD-WAN box. Yes. The word "Magic box" is quite often used in SD-WAN conversations. So let's talk about the different ways these magic boxes auto-magically make 2 internet connections or a MPLS + Internet connection transform your network to the modern era where SD-WAN providers are starting to offer 100% uptime SLA's.

There are over 20 different SD-WAN OEM manufacturer's that I am aware of at this time. Let's narrow it down to some more specific groupings based on the way providers offer service that they are marketing as SD-WAN.

4 General SD-WAN topologies:

There is a lot of variation and strengths and weaknesses that can be discussed between each SD-WAN vendor within each of these categories. The below however will give a starting point to seeing the 4 main methods that are being deployed by providers that are offering a SD-WAN service.

Path Selection - Selects which path each application should go through (2 or more circuits) and uses a second path as failover. This isn't a lot different than old fashioned failover other than each path is being used active/active. It does not optimize each packet or session.

Session Based Routing - Selects which path down each circuit (2 or more) is fastest for each session. This does not optimize packet by packet.

Dynamic Packet Based Route Selection - Packet by packet decision making for which path is the optimal path to reach its destination. If the optimal path changes at any point then dynamically the next packet will go down the path that is now preferred. This option is designed to maximize the best path for each packet through the first mile, middle mile and last mile to reach its destination in order.

Cloud WAN Optimization - I am not really sure what a better name for this is but there is also a SD-WAN play out there that offers a global Middle Mile WAN optimization to shorten latency over long distances. The client then just needs to procure local internet connections from whomever they want at each end point to access the closest entry point to the middle mile optimized network. This product is designed to replace the MPLS network core, eliminate dependency on a single provider that is marking up the price for each access link, optimize the longest part of the route. This is huge for global players because getting a local internet connection outside the US with fast customer service is much easier in lots of countries with less developed telecom infrastructure than it is for a Global MPLS provider to get a competitive option into most developing nations. This option is not dynamically optimizing packets on 2 local internet circuits. It is more of a MPLS replacement SD-WAN product. A single connection is all that is needed. This isn't the longest section because it is my favorite. It is just the hardest to explain.

I certainly have a lot of thoughts about which providers are strong SD-WAN players and which ones have a weak offering but I will save those thoughts for customer presentations. The purpose of the article was to just help our client base get a better feel for the general buckets pretty much all the options fall into when they are seeing just about every carrier and traditional hardware vendor go to market with something they are calling SD-WAN. Like everything else....the details are extremely important and some of these SD-WAN options are tremendously more powerful than others in the value they provide. All SD-WAN is NOT created equal. Not even close.