For viewers (students), we recommend users have (at least) 0.5 Mbits/sec -- which is 500 Kbits/sec -- upstream bandwidth, and (at least) 1 Mbits/sec download bandwidth. The upstream bandwidth is the amount of bandwidth their computer has available to transmit data to the BigBlueButton server.
These are not hard and fast numbers, as it depends on the activity of the viewer. If the viewer is not broadcasting any webcam, the amount of upstream bandwidth used would be less than 0.5 Mbits/sec.
A good way for users to check their bandwidth is to visit speedtest.net. The results from speedtest.net give the user's actual bandwidth. This actual number is important because a user may report that their ISP provides them 0.5 Mbits/sec upstream bandwidth; however, speedtest.net may report an actual number that is much lower. The difference may be throttling by the ISP and background activity on their computer (such as background downloads, file sharing clients, other users on the network, etc).
For presenters, we recommend as much upstream bandwidth as possible. For example, if the presenter shares their desktop, then BigBlueButton's desktop sharing will attempt to publish their desktop updates as quickly as possible to the server.
For more answers to Frequently Asked Questions regarding BigBlueButton, please check the link below. If you need further technical assistance, please contact FNU IT at 859-899-2525 or email us at firstname.lastname@example.org. Thanks.