The ultimate dream protocol is one in which a sender just encodes bits in a certain way such that the receiver will get them, and puts them on the line without

The ultimate dream protocol is one in which a sender just encodes bits in a certain way such that the receiver will get them, and puts them on the line without any handshaking or synchronization. I don’t think this is impossible. The space of orthogonal codes across time and frequency could be chosen to be practically infinite, therefore, any random selection of two such codes would look like white noise to each other. The receiver would have to listen on a large subset of such channels all at once, which is not practical in real-time, but could be practical looking backward at the stored waveform from some carrier channel that all such possibilities have in common. It would commonly miss single bits and large chunks of data, so it would have to have FEC across multiple scales of code, frequency, and time. This works for large messages, but smaller messages would have to be sent over a channel with bandwidth narrowed to consume the time window of detection. Thus you should have a fair guarantee that either every message will be received during the detection window, or no message will be received, and this could be the job of network infrastructure to monitor and buffer as necessary. If that fails, then, well, maybe let the application layer deal with it.