please can anyone help me understand how UDP handles out-of-sequence VOIP datagrams? will UDP pass the datagrams that arrive out of sequence up the other layers of the OSI model or will it drop these out-of-sequence datagrams?
UDP will pass them up to the next protocol layer, which is RTP. RTP will either place then in a buffer to be played out or, of they are too late, will disregard them.
It must be this way, because UDP does not know how late they are. The timestamp is part of the RTP protocol.