On Fri, 13 Dec 2019 12:00:52 +1300, Peter Reutemann quoted:
'Last month, the engineering department at Slack—an instant messaging platform commonly used for community and small business organization—released a new distributed VPN mesh tool called Nebula.'
Here <https://arstechnica.com/gadgets/2019/12/how-to-set-up-your-own-nebula-mesh-vpn-step-by-step/> is a followup article explaining how it works in more detail. All VPNs are capable of establishing bidirectional connections in and out of private networks. What makes Nebula a “mesh” VPN is the fact that it can dynamically reconfigure itself to take advantage of more direct connections between private networks, instead of always routing through public “lighthouse” nodes. It does this by spoofing source addresses on UDP packets, which usually (!) works.