How can a dynamic network of producer brokers be configured to talk to a dynamic network of main/consumer brokers in a concentrator topology as discussed in Ch 6 Network Topologies (http://fusesource.com/docs/esbent/7.1/amq_networks/FMQNetworksTopologies.html). All the examples for using multicast in the transport connectors use discoveryUri="multicast://default". Also, if each producer broker publishes to each node in the main/consumer broker layer in a round robin, how is the network connector specified?