How many concurrent VPN connections can El Capitan Server (10.11.1) Support?

I'm trying to locate any information on how many concurrent VPN connections OSX server can handle.

I Understand That:

1. internet Bandwidth is a bottleneck. For this discussion let's pretend there is unlimited Bandwidth.
2. The number of IP addresses you assign to the VPN service is a limit. Let's assume we are on the 10.x.x.x network.

In the scenario outlined, you could provide IP addresses to millions of clients. But I can't imagine that an average Mini Server could have the processor capacity to support millions of concurrent VPN connections.

Any advice is greatly appreciated,

Chris