How Does SD-WAN Work?

SD-WANs have the potential to reduce your WAN costs by up to 90% if you are using an MPLS network today.  How is this possible?  Sometimes, a picture says more than words.  Or at least makes it easier to understand.  Let’s say you have an MPLS network today.  You can add low cost broadband internet and LTE and the SD-WAN will create encrypted VPN tunnels to include these circuits in your WAN:

The magic is that the SD-WAN devices will sense the quality of all the connections for a specified data path and route the traffic across the best path, based on rules that you specify in their cloud control panel.   It does this by:

  • Continuously measuring one-way packet loss, latency, jitter and available bandwidth on each path.
  • Aggregating bandwidth across all connections, so they can even be used for a single flow. (Dependent on SD-WAN provider)
  • Avoid loss and mitigate its effects before they become a noticeable problem, as with brown-outs or rising packet loss.
  • React in sub-second interval (~2.5 times the RTT) to changing performance characteristics to direct traffic down the best link.  For example, if the latency is 30ms, the reaction is 75m. (Dependent on SD-WAN provider).

If you have a call center, some SD-WAN providers will replicate traffic on two different paths, optimizing VoIP or video to allow cheap broadband bandwidth to be used in place of MPLS or private lines.

By using two broadband or dedicated internet access circuits with 99% reliability, the overall reliability rises to 99.99%

  • Overall Reliability = 1-((1-0.99) x (1-0.99))= 99.99%

The reduction in your WAN costs is generated by the use of lower cost internet circuits for bandwidth.  If you have a 5M MPLS circuit at a location and need 10M, you add a lower cost 5M internet circuit, saving hundreds of dollars.  Eventually, you develop the comfort level that this technology really works and you might reduce your MPLS port size or eliminate it completely, when your contract expires.  Plus, you manage all the network devices from a single web portal.

Selecting the right SD-WAN platform takes a great deal of education.  Adding internet links to your MPLS WAN is a painless way to start.  Or, if you use internet VPNs today for your WAN, SD-WAN will improve the performance, flexibility and your visualization of your wide area network.

There are many interesting technologies out there, but they are not all alike.  You also want to be sure that the platform you select will be around for the long term.  Speak to the pros at SASE Experts to learn more.

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