Server to Server bandwidth

Hi, hopefully someone will be able to assist in this as it is causing us major dramas.

I have Openfire 3.6.4 and psi client running on four different servers, each server in a different LAN, each LAN connected by 256Kbits private sat link.

Each server has up to 10 chat rooms with an average of 200 users per chat room.

Each location has all their clients connect to the local server but they will join rooms in other servers.

Every day we are finding the openfire connection drops between servers and we have to reboot the servers to establish cross site comms with openfire.

(users drop out of the room, can connect to a room or sometimes can not even browse the rooms).

Is their a bandwidth limit or QOS minimum requirement ?

Are their ping settings we can change to test the minimum requirement for Openfire as I am concerned it is because of our sat hops.

Many thanks for any help.