A segmentation server defines a segmentation policy and distributes the segmentation policy to be enforced by a plurality of operating system (OS) instances. The segmentation policy includes rules controlling which workloads executing on the OS instances can communicate with other workloads and controlling how the workloads may communicate. When a connection between two OS instances is requested, each OS instance provides an identity and a cryptographic proof of the identity. The OS instances each authenticate the identity received from the other OS instance, and once authenticated, determines based on the authenticated identities if the rules permit the communication. If the rules permit the communication, the OS instances obtain session parameters that enable the OS instances to validate integrity of the messages communicated between the workloads and optionally encrypt the messages.