 In particular, the use of SYN cookies allows a server to avoid dropping connections when the SYN queue fills up.Instead of storing additional connections, the SYN queue entry is encoded into the sequence number sent in the SYN+ACK response.If the server then receives a subsequent ACK response from the client with the incremented sequence number, the server is able to reconstruct the SYN queue entry using information encoded in the TCP sequence number and proceed as usual with the connection.