Patent ID: 8925068
Filing Date: 2014-12-30
Classification: H04L

Abstract:
1. A method of preventing a denial of service (DoS) attack using transmission control protocol (TCP) state transition by monitoring flow of packets transmitted between a client and a server using TCP, the method comprising the steps of: when the server receives a connection request (SYN) packet of the client, switching a TCP state of the server from a listening (LISTEN) state to a connection-request-received (SYN_RCVD) state; and after the server sends a connection-request acknowledgment (SYN/ACK wherein, if the server receives the same SYN packet again in the ACK_WAIT state, the TCP state of the server is switched from the ACK_WAIT state directly to a closed (CLOSED) state and safely terminating a TCP connection, wherein, if the server receives a finish (FIN) packet in the ACK_WAIT state, the server sends an acknowledgement (ACK wherein if the server does not receive an packets during a previously set timeout period in the CLOSING state, the TCP state of the server is switched from the CLOSING state directly to the CLOSED state, and the TCP connection is safely terminated.