Network QoS implementation

Is there more information for “Missed packets - Forward error correction” and other features of QoS networking ?
Is it inserting “XOR-ing” packet after packet set to recover from random lost of one previous packet in packet set (or other proprietary and/or patented technology) (Adaptive Forward Error Correction (AFEC) based Streaming using RTSP and RTP) ?
Is the selective acknowledgement (ACK/NACK) and repeating packet used (UDP use was confirmed as transport technology) (or not due to increased latency) ?
Is some sort of packet scheduler used like HTB in linux traffic control ?