What will happen if the final ACK for three-way handshake is dropped?

0
votes

Based on TCP state transition graph, when server(passive open end) has sent SYN,ACK to client (active open end), and client received it and sent ACK to server, but is dropped in the network, what will happen?

It seems like, client will go into ESTABLISHED state and server won't, but client doesn't know this...

1
networkingtcp
First, TCP doesn't have servers or clients. The client/server concept is an application concept that TCP doesn't have. TCP sets up connections between peers. Either peer could be the client or server for the application, but TCP doesn't care. – Ron Maupin
The server will re-send the SYN/ACK. – user207421
@EJP Any reference for that? – A.Stone
@RonMaupin I rephrased the terms – A.Stone
My reference is RFC 793. The SYN part of the SYN-ACK is a TCP segment like any other and is therefore subject to retransmission until ACK'd or the timers expire, at which point the connection is reset. – user207421

1 Answers

1
votes

The SYN/ACK is retransmitted. See RFC 793. The SYN part of the SYN-ACK is a TCP segment like any other, and is therefore subject to retransmission until either it is ACK'd or the timers expire, which causes the connection to be reset.