The bandwidth need is very different, depending on how you configure and run Orchestra.
For an Orchestra not using any special integrations, or for example Calendar, global variables, or media sync, the only data sent between the central and distributed Queue Agent are stat messages, as well as a keep alive message sent every 30 seconds.
Stat messages for a Visit are less than 3 kb in size and Service Point sessions are less than 5 kb in size. The needed bandwidth is thus depending on how many Visits and Service Point Sessions you have in your system.
However, when synchronizing a new Agent Profile or media, the bandwidth requirement is much larger.
Internal tests have been performed, with bandwidth as poor as 250 kbit/s as well as 4% packet loss. Profile and media synchronization still works under those conditions, but it is recommended to have higher bandwidth available.