Create a network of brokers via AMQP links such that a client can publish a message and have it routed to downstream brokers via the address in the AMQP header.
Use case: local broker that a client interacts with and publishes a message to a destination that does not exist on that broker and the message is routed to the broker with that destination.
Use case 2: client creates a dedicated destination for responses (could be a temporary queue). The client sends a message to a known destination the consumer of that destination can publish a response to the client's reply to even if the client is not on the same broker.
Use case 3: a group of brokers that are "load balanced" clients can connect to any broker and publish/receive from destinations on the other brokers. This would be used in a cloud/horizontal scaling environment.