2009, mobile networks class. We were studying how TCP handles packets lost over 3G: the network detects the loss, replays the packet, and the transfer survives a radio link that drops things all the time. Someone asked the obvious question: why not just make the radio link reliable in the first place? The professor's answer became the soundtrack of that semester: there is no free lunch. Reliability over 3G is not free, it is paid for in retransmissions, latency and battery. The cost never disapp...