Bit Offset,Name,Reference,Assignment Notes
4,Reserved for future use,[RFC9293],
5,Reserved for future use,[RFC9293],
6,Reserved for future use,[RFC9293],
7,AE (Accurate ECN),[RFC-ietf-tcpm-accurate-ecn-34],"Previously used as NS (Nonce Sum) by [RFC3540], which is now historic [RFC8311]."
8,CWR (Congestion Window Reduced),[RFC3168],
9,ECE (ECN-Echo),[RFC3168],
10,Urgent Pointer field is significant (URG),[RFC9293],
11,Acknowledgment field is significant (ACK),[RFC9293],
12,Push Function (PSH),[RFC9293],
13,Reset the connection (RST),[RFC9293],
14,Synchronize sequence numbers (SYN),[RFC9293],
15,No more data from sender (FIN),[RFC9293],