MassTransit is free software/open-source .NET-based Enterprise Service Bus (ESB) software that helps Microsoft developers route messages over MSMQ, RabbitMQ, TIBCO and ActiveMQ service busses, with native support for MSMQ and RabbitMQ. It supports multicast, versioning, encryption, sagas, retries, transactions, distributed systems and other features. It uses a "Control Bus" design to coordinate and the Rete algorithm to route. Since it does not include "business monitoring" or a "business rules engine" (and requires programming to implement sagas for orchestration), MassTransit is typically considered to be in the category of "lightweight ESB" software.