NServiceBus transports can be divided into several categories.
Federated transports are inherently distributed. Each endpoint instance may connect to a different node of the queueing technology. Messages are routed transparently between the nodes but the physical routing layer needs to contain information as to which node particular endpoint is connected to.
Federated transports include:
Broker transports are inherently centralized. Even if there are multiple servers, they act as a single logical instance that hosts all the queues (and/or topics/exchanges).
Broker transports include:
Unicast-only transports do not have the notion of topics, exchanges, or similar concepts; only queues. Because of this, they allow only point-to-point communication. Sending a message to multiple receivers (e.g. publishing an event) involves of multiple transport-level sends. Unicast-only transports require subscription storage via NServiceBus persistence.
Unicast-only transports include:
Multicast-enabled transports have some notion of topics, exchanges, or similar concepts, which allow sending a message once and having it received by multiple clients. These transports do not require subscription storage.
Multicast-enabled transports include: