WebRTC has built in mechanisms to check how many bytes have been buffered (RTCDataChannel.bufferedAmount), and you can register a low water mark (RTCDataChannel.bufferedamountlow) that fires an event handle when the buffered amount goes below that threshold (RTCDataChannel.onbufferedamountlow) where you can resume sending.
WebRTC is sort of a combination of low-level and high-level APIs, but the ability to control backpressure ends up being very useful.
