If an SD-WAN and an MPLS connection have the same bandwidth, which offers better performance? The prevailing wisdom is the MPLS connection since it’s managed, but that’s not necessarily the case, as we learned from one customer. Internet performance has improved so much in the past two decades that its performance can rival and even exceed that of private WAN services.

In this case,  the company, a manufacturer, was considering switching from MPLS to SD-WAN. The company had 17 offices spread over U.S., Asia Pacific and Latin America. The offices were connected to the LA data center via MPLS. The company wanted to use SD-WAN in Latin America.

During our evaluation of their network, we turned up some very unusual results. The deviations of a managed network should not exceed one or two-hundredths of a second; however, some of this company’s routes had a latency fluctuation of up to one-tenth of a second:

(Note: ICMP pings only provide an approximate picture of a route’s latency; since they are considered low priority traffic, the response may be slower. Instead, a more accurate way to measure is by simulating data plane traffic using a traffic generator for the transit traffic.)

What caused the varying latency? One reason may be policy; but on the other hand, no service provider has a global communications network, and connecting distant regions will always be an issue.

To complicate matters, service providers often partner with local companies to fill gaps in their network. The quality of local infrastructure can vary considerably, and may not be appropriate to the volume of traffic coming in; such a scenario would cause delays for peak time traffic. Likewise, different companies set routing policy based on local needs; American network habits are not relevant in Indonesia and may, therefore, receive a lower priority rating.

The question of whether or not a better alternative exists is no less important than that of why certain offices are seeing unusual latency. One readily available alternative is the internet. Take a look at the difference between Mexico and Costa Rica:

Though Costa Rica seems to pretty consist when measuring MPLS vs internet connections, Mexico’s MPLS scores are significantly poorer than their internet scores.

Don’t believe that MPLS performed worse than the internet for offices just a thousand miles away? We tested it again – and found that the internet in Mexico had sixty-six percent less latency than MPLS. In fact, multiple internet connections would still be required for redundancy.

Certainly, MPLS will still generally provide superior performance to internet-based WAN. However, our results underscore the necessity of systematically examining the network to determine what means connection medium is optimal for your business, and not relying on jingles and catchphrases. Network performance is extremely variable and therefore anyone, whether in finance or engineering, must test a network’s actual performance before making connection decisions.

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