Discard packets without fixed bit or reserved bits set. Section 17.2 and 17.3 of QUIC transport: Fixed bit: Packets containing a zero value for this bit are not valid packets in this version and MUST be discarded. Reserved bit: An endpoint MUST treat receipt of a packet that has a non-zero value for these bits, after removing both packet and header protection, as a connection error of type PROTOCOL_VIOLATION.