Flags

These are used to alter the way flows get managed. Flags are commonly used in various headers to specify certain actions; major ones include OFPXMT_OFB_TCP_FLAGS used in TCP header (EXT-109). This field is used to match all flags, such as SYN, ACK, and FIN, and can be used to detect the start and the end of TCP connections. Another common flag is OFPC_FRAG_REASM, which reassembles IP fragments before pipeline processing.