The three-way handshake model is very important.

During this interval of events, host C can launch a spoofing attack by sending lots of packets. The client will discard this ‘ACK’ packet and tell the server to terminate the connection. But the server will enter the deadlock state, waiting for the client to send the data.Īnother problem is that if a host C sends a connection request to the server by impersonating the client, the server will respond back with an ACK to the client. This packet will be dropped by the client because it did not intend to connect. If the server receives such a packet, it will respond back with an SYN+ACK packet. In the above case, if a connection is not going on between client and server, the arrival of an old duplicate connection request packet still causes problems. When it receives this old packet with the same sequence number ‘z’, it unknowingly accepts this old packet and discards the actual packet from the new connection. At some time during the new connection, the server is accepting a packet with a sequence number ‘z’. This old packet has arrived from a previously closed connection and contains a sequence number ‘z’. Suppose that an old duplicate packet arrives at the server machine. The two-way handshake model failed due to an old duplicate packet problem. Problems with the Two Way Handshake Model Let us first see the problems with the two-way handshake model. In this guide, we will see how the three-way handshake mechanism works.

TCP uses a three-way handshake mechanism for establishing a connection between two devices. Since it is connection-oriented, a path or connection needs to be established before transmitting any data. Request For Comments (RFC) 793 defines the TCP as a reliable and connection-oriented protocol. TCP or Transmission Control Protocol is a standard transport layer protocol that the internet uses to transmit data.

Packet capture tool three way handshake