how many xbees (s1 pro digimesh firmware) can be in the same network at the same time

Hi I am using the latest digi-xbee library for python, and want to know limits in the network number of devices (inside the range and outside of the range or off devices), the number of actual devices conected between them simultaniously, the number of concurrent near by devices. I suspect the payload and quantity of messages does matter, is there any phisical or logical constraint should I take into account? for example when you call discover network is there a limit in the number of devices that can be discovered?