Nebula

Nebula is a scalable overlay networking tool that provides an easy and secure way to connect tens of thousands of computers, which can be hosted by different cloud service providers in various locations. Developed by Slack Technologies, the tool encompasses encryption, tunneling and group security, standards that are basically mandatory for anyone who needs to connect over the Internet for professional activities nowadays.

The idea of the utility came out of the need to find a replacement for IPSec, a protocol that was used to provide encrypted connectivity between regions. While IPSec managed with a smaller network infrastructure, it soon proved to be inefficient mostly because of the difficult network segmentation which occurred when cross different network boundaries.

In addition to encryption and security, the solution also enables high-level traffic filtering, a concept that entails that the individual nodes can allow or deny traffic using the identity of the connecting hosts. As you probably hinted, the hosts are required to identify via certificates which are issued by an authority that encodes user-defined attributes such as data center, environment or role, for instance, when attempting to connect to peers. The modus operandi has the benefit of being faster as the latency is reduced between the hosts.