Who negotiates bandwidth

In WebRTC connections, it is seen sometimes that some video streams have reduced bandwidth. I wonder how if/how it is implemented in OpenVidu.

Is it only the publisher which can set the bandwidth? In such a case, does adaptive bitrate is supported by WebRTC/OpenVidu? If not, can you imagine a situation, when the video published by a low-bandwidth client stalls almost completely, because the same cilent is forced to receive high-quality streams of other publishers?