10.3.5. Federation Topologies

A federated network is generally a tree, star, or line, using bidirectional links (implemented as a pair of unidirectional links) between any two brokers. A ring topology is also possible, if only unidirectional links are used.

Every message transfer takes time. For better performance, minimize the number of brokers between the message origin and final destination. In most cases, tree or star topologies do this best.

For any pair of nodes A, B in a federated network, if there is more than one path between A and B, ensure that it is not possible for any messages to cycle between A and B. Looping message traffic can flood the federated network. The tree, star and line topologies do not have message loops. A ring topology with bidirectional links is one example of a topology that causes this problem, because a given broker can receive the same message from two different brokers. Mesh topologies can also cause this problem.