If you ask a group of 10 people what SD-WAN is, there’s a good chance you will get 10 different answers. So, which one is right? Well, that depends on your perspective. If you take all the marketing and jargon out of the equation it will be something like this:
Let’s start off with what the acronym stands for. SD-WAN is a Software Defined Wide Area Network. It is a fresh new approach to how you build your WAN to accomplish the following objectives:
- Move from legacy packet networking, which frequently holds the business back, to an application-policy based approach to build your WAN infrastructure. This is a fundamental shift that is an essential prerequisite for the modern remote office.
- Eliminate dependencies on your network service provider. Gain the freedom to utilize disparate and sometimes cheaper forms of connectivity to deliver data reliably to remote offices.
- Make your enterprise and WAN truly cloud-ready. Decouple policy and infrastructure so your applications can be delivered to the remote office from the cloud/SaaS/data center in a consistent manner.
- Eliminate dependencies on proprietary hardware. Gain cost savings and a rapid innovation cycle aligned to business needs.
- Deliver a great user experience with native application and network analytics that are automatically applied to the network in a self-healing manner.
In addition to business and architectural transformation, SD-WAN delivers hard cost savings. This technology can reduce both OPEX and CAPEX expenditures depending on the solution deployed. The OPEX expenditures are significantly reduced not only through the deployment stage, but throughout the ongoing life cycle of the network.
I’ll present a common scenario for SD-WAN deployment. The retail sector provides us with a simple cost-benefit analysis for this technology. Having worked at several large retailers, I can tell you that one of the largest cost centers is connectivity to the retail stores. Typically, a store will have a primary connectivity method of MPLS, with a secondary backup of an IPSEC VPN and sometimes tertiary redundancy of something like 4G or satellite. If you look at the costs associated with each of these technologies, it is easy to see why some retailers can pay in excess of $5,000 to $8,000 per month to connect a single remote site back to the enterprise. One retailer I know pulls in four T1s, a 20Mbps Internet circuit, and 4G for each store. The four T1s account for $800 per month in circuit and local loop charges while only providing roughly 8Mbps of bandwidth. With MPLS charges on top of that ranging from $300 to $600 per megabit per month, the costs have now blown up to $5,600 per month to provide ongoing service. Even with a small footprint of let’s say 100 retail sites, your monthly recurring costs have jumped to a little over one half million dollars.
If you take the same scenario outlined above, only utilizing an SD-WAN solution based on dual internet the costs subside considerably. Dual internet circuits from disparate providers will provide you with 40Mbps of usable bandwidth compared to the 8Mbps and a huge savings.
MPLS providers are constantly using the argument that their circuits can provide zero packet loss. However, with MPLS being a shared medium of all the customers who are part of the providers network, packet loss can and does occur. If you take a close look at your contract you will see that there is an SLA as to how much packet loss is acceptable. SD-WAN compensates for the small amount of packet loss that will be evident over commodity internet circuits by implementing Forward Error Correction. This allows the SD-WAN cloud to reconstruct any missing packets to deliver results rivaling or even in some cases surpassing MPLS alone.
The additional control you receive for application assurance is another big reason to consider SD-WAN. Being able to accurately identify and prioritize traffic to ensure service availability helps in reducing support calls and poor application performance issues.
Operational benefits are also more evident in SD-WAN than legacy technologies. SD-WAN is policy driven by nature. Managing a complex WAN of hundreds of sites can take specialized engineers a significant amount of time to provision, manage, and troubleshoot. With SD-WAN the policy controller handles all the tasks mentioned above in a holistic manner. Where it would usually take 10 to 20 hours to bring a new site on with legacy technologies, that time can be brought down to minutes. The savings in manpower as well as removing the issue of human error can save a company considerable amounts.
SD-WAN is a policy-driven overlay that moves the paradigm from local based configuration element changes such as routes, ACLs and VLANs to business apps, sites and links. The overlay manages the underlying infrastructure based upon business and operational policies in a holistic manner, providing for more advanced monitoring and resilience in connectivity.