This solution uses replication to share information between primary servers and make them highly available. The solution also uses fan-out to spread the data from the primary servers behind the firewall to secondary servers in the de-militarized zone (DMZ) .

Figure 1. Architecture using replication and fan-out

1. Three clients register handlers with the Diffusion™ servers behind the firewall. These clients can be located on the same system as the servers or on remote systems. Each Diffusion server load balances requests between clients that have registered to handle requests of that type. If one of the clients becomes unavailable, the requests can be directed to another client. You can connect more client sessions to deal with higher volumes of requests.
2. The Diffusion servers inside the firewall replicate information into a datagrid. If a Diffusion server that was handling a client session or topic becomes unavailable, the responsibility for that client session or topic can be passed to another Diffusion server that has access to all the information for that session or topic through the datagrid.
3. The Diffusion servers outside of the firewall, in the DMZ , are configured to use automated fan-out to connect to the Diffusion servers inside the firewall. Specified topics on the primary server are fanned out to the secondary servers.
4. You can use a load balancer to spread requests from subscribing clients across many secondary Diffusion servers. If a server becomes unavailable, clients can be directed to another server.