You are absolutely right. But we need to remember - our motivation is to get a solution without most of TCP mechanisms to suit cases where it is not required. S

You are absolutely right. But we need to remember - our motivation is to get a solution without most of TCP mechanisms to suit cases where it is not required. SCTP - is more of an alternative to TCP and implements mechanisms that are not required by our motivation. DCCP - is more close to what we want as it solves security concern: congestion collapse. And you are right - we do not want reinvent the wheel.