If a link in the path cannot handle all currently requested packets (in whatever protocol) then one of the endpoints needs to decide what to send and what to de

If a link in the path cannot handle all currently requested packets (in whatever protocol) then one of the endpoints needs to decide what to send and what to delay/drop. It can do this randomly, sequentially (youngest/oldest) or try to be smart about what causes least impact. A few systems I saw would, in this case, heavily favor dropping UDP on the assumption that the applications using it can handle dropped packets in stride; plus, dropping TCP packets only causes more traffic in the short term due to retransmissions. In this case the drops could have nothing to do with buffer sizes -- UDP packet can still be dropped even if it is the only UDP packet in a large buffer.