As SD-WAN adoption matures and moves from “peak of inflated expectation” to “slope of enlightenment”, a question that I hear and many technologist ponder over is whether SD-WAN is the new MPLS. If you asked this question to a distinguished engineer they would violently disagree at a technical level comparing the difference from an OSI layer and packet/protocol formats perspective. Comparing from a business and qualitative perspective, the weighing scale could tip more towards agreeing that SD-WAN is the new MPLS.
When it comes to networking, right from its origination, the main objective has always been around providing a fabric to stitch applications together.
Although SD-WAN is an overlay technology, expectations (Voice of Customer) still need to be met to provide the appropriate application experience, availability of the network fabric and resiliency of the solution for 5 9’s of SLA.
The following are key attributes of SD-WAN that make it a serious contender to become the new network fabric:
Connectivity: The endpoints that send and consume network traffic haven’t changed a lot but the traffic pattern mix has definitely changed over the years with a majority of the traffic going or coming out of the cloud endpoints. In typical hub-spoke topology that Enterprises have deployed for a long time the hub is now evolving from an enterprise owned hub site to a cloud hub which is either enterprise outsourced data center or a virtual private cloud in a public cloud like AWS/Azure/IBM/GCP. The key being SD-WAN provides the orchestration to take the IT + Application intent and translates it into a unified seamless secure network fabric across those endpoints. Whether you deploy a full mesh or hub-spoke topology for network fabric, SD-WAN is able to orchestrate the application experience across those topologies.
Network Resiliency and High Availability: For many years, network resiliency has been measured at the link, node and network level. To deliver an exceptional application experience, IT resorted to using 3rd party tools to measure application performance. A common requirement for 5-9’s in MPLS have been technologies like ISSU (in-service software upgrade) and fast re-route (FRR) to maintain high network availability. As distributed systems and computing have become the norm, resiliency is being addressed in 2 ways. One is to focus on application resiliency and provide the necessary infrastructure redundancy like Dual-CPE (dual spoke), dual SD-WAN GW/hub’s, multiple WAN links with application QoE to provide application resiliency within milliseconds of any network component failure. Another focus in on using web scale micro-services based software for SD-WAN controller where constant upgrades/downgrades, workload moves across availability zones, scaling the number of endpoints up and down are the norm without impacting the application experience.
I am not saying MPLS will go away but we will start seeing SD-WAN as the basis for most network fabric since it connects the applications to network layer in a more integrated manner than MPLS did. Also SD-WAN could be deployed with and without an MPLS under layer helping SD-WAN service providers and consumers to be attain Application SLA without having an e-2-e MPLS network fabric.
This is just a perspective meant to help establish confidence that SD-WAN is carrier grade and has a chance to become the network fabric of the future.