How to send large packets using TCP?

SYN flood sends a flood of TCP/SYN packets, often with a forged sender address. Each of these packets are handled like a connection request, causing the server to spawn a half-open connection, by sending back a TCP/SYN-ACK packet, and waiting for an TCP/ACK packet in response from the sender address. However, because the sender address is forged, the response never comes. These half-open connections consume resources on the server and limit the number of connections the server is able to make, reducing the server's ability to respond to legitimate requests until after the attack ends.