Doc: Federated Queues and Addresses

Currently Artemis supports linking of brokers via clustering that are within the same DC or AZ.

It is not sensible to form clusters though over high latency or unreliable networks, e.g. WAN, cross-region in cloud, hybrid on-off premise etc.

Bridges exist, but these are static.

In ActiveMQ5 there was a concept of Network of Brokers, and like wise in RabbitMQ there is a concept of Federation, both of these try an deal with this issue.

This is to implement similar functionality in Artemis.