HotStuff

• A consensus system created by researchers at VMware, Cornell an UNC Chapel Hill. A new BFT protocol that provides both linearity and responsiveness. Emin Gun Sirer says one of his students, Ted, was the lead author.
• One of the authors works at (11-2019) AVA Labs, together with another Cornell employee, Emir Sirer.
• Short description: basically the system has a bunch of 'leader' validator nodes that process transactions on the network, while risking their own money if they try to cheat the system.
• HotStuff will be the consensus protocol behind the Libra BFT blockchain. For a look into HotStuff check out this link.

From the above link:

• "The first change made by HotStuff to other BFT systems, and the most important one, is to change PBFT’s mesh communication network to a star communication network, which means each communication will rely on the leader. The node no longer broadcasts the message to other nodes through the P2P network, instead, it sends the message to the leader, which processes it and sends it to other nodes. Thanks to the star communication network, the communication complexity of the system has been greatly reduced. Similar to PBFT, the leader proposes a state transition request, and other nodes check its legitimacy after receiving the request.
• The second important change HotStuff made is to merge the view change process with the normal process, which means there is no longer a separate view change process, thus reducing the complexity of view change. It can be seen that during view change in HotStuff, a node in the system does not need to confirm the message “enough nodes want to carry out view change” before notifying the new leader, instead, it can directly switch to the new view and notifies the new leader. HotStuff puts the behavior of confirming the message “enough nodes want to carry out view change” into the normal process. This is a new approach, but it will inevitably lead to a new phase of confirmation for the normal process. Therefore, HotStuff extends PBFT’s two phases into three phases."
• For a comparison between PBFT, Tendermint, SBFT and HotStuff look here.