Message Packets on Server to Server Link

I did a packet trace on the server to server link between two Openfire servers in my lab and found that during a conference when a message is sent from the conference server to another server it is always sent twice. Can anyone explain this?

I have one server hosting the conference connected to another server which is hosting 3 separate clients, all on different machines on a separate network interface from the conference server. When I send a message from the conference server (via a Spark client connected locally) the message is sent to one of the Spark clients on the other server and then sent again to another of the 3 clients but all three still receive the message. I have tried the same test with 4 and 5 clients and it is always the same result. So, is this a bug, should only one message be sent across the server link or should one message be sent for each client? Thank you for your help.