Customers often want to know the number of core aggregator nodes they need to support their initial deployment and planned growth. In fact, it’s one of the most common questions I’m asked during the SD-WAN sales process.
Coming up with an easy answer is tough because accurately sizing SD-WAN deployments depends on many factors — factors that change a lot based on actual usage by end customers.
Accurately Sizing SD-WAN Deployments
Our recommendation is to deploy 50-75 sites per Aggregator/core node based on the estimate of each site consuming 150-200Mbps bandwidth per site. In the real world, as with most network solutions, few customers reach and sustain this amount of traffic for any length of time, therefore some overprovisioning is possible. How much is hard to tell until the SD-WAN solution goes into production in the customer base.
The key to sizing SD-WAN deployments is to realize there is no magic number of Aggregators that can be generalized across all situations, all the time. And this is largely due to the flexible nature of SD-WAN and other variables that may be introduced. For example, bandwidth consumption, link aggregation, encryption, QoS, and other features may cause Aggregator server load increases or decreases.
Use Case Studies to Frame Sizing Estimates
To help channel partners with sizing SD-WAN deployments, I often like to share several customer use cases to provide some real-world indication of possible sizing needs. I base my recommendations on these use cases because it’s impossible to provide 100% accurate sizing estimates.
To restate, we recommend that customers deploy each Aggregator on a server with 8 cores, 10Gb NIC, and a 100Gbps network connection to support 50-75 sites or connected CPE devices consuming 150-200Mbps bandwidth. That said, we do have partners that overprovision their bandwidth by 10, 20, and even 50 times.
Ultimately, it really comes down to how comfortable a partner is with their end customers’ usage patterns.
To further illustrate how use cases help inform deployment designs, consider this (possibly exaggerated) scenario:
Logan (our VP of Sales) and I have the same car with the same tires, which we purchased at the same time. The tires are rated for 100,000 KM of service. I drive like my grandpa: slow, steady, no excitement. Logan is like a rally driver: careening around corners, accelerating suddenly, and braking hard. Lots of excitement and lots of demand on his tires. Logan goes back to the tire store in three months after driving 30,000 KM and his tires are bald. I also return the same day, with the same distance driven, but have 90% of my tread left. My tires will clearly get to or even exceed the rated 100,000 KM.
So why the difference? Because not all the variables are the same! It comes down to how those tires are being used. Burning rubber like a wild man or slow and predictable driving? When it comes to sizing SD-WAN deployments, your customers’ needs can be as different as me and Logan.
While in one case you might find that you can get 100 customer sites or more per Aggregator node, you may realize much fewer if your end customers are really pushing the system hard. As they say, actual mileage may differ.
Need help with sizing SD-WAN deployments? Contact Multapplied today.