Why need Ack flag if we already have ack number in TCP The ACK flag indicates that the Acknowledgment Number field is significant, ie containing a meaningful value When a socket connection has already been established that is nearly always the case, but it isn't while a connection is being established Acknowledgment Number: 32 bits If the ACK control bit is set this field contains the value of the next sequence number the sender of the segment
NACK vs. ACK? When to use one over the other one? 23 Personally I don't even feel that there is a need for ACK It's faster if we just send NACK (n) for the lost packets instead of sending an ACK for each received packet So when which situations would one use ACK over NACK and viceversa?
Why do I see a RST, ACK packet instead of a RST packet? SYN --> <-- SYN ACK ACK --> In the case of a RST ACK, The device is acknowledging whatever data was sent in the previous packet (s) in the sequence with an ACK and then notifying the sender that the connection has closed with the RST The device is simply combining the two packets into one, just like a SYN ACK
TCP ACK confusion - Network Engineering Stack Exchange The receiver can also selectively ACK (SACK) 51-100 to avoid a retransmission of successfully received segments Without selective ACK, the sender retransmits 50-100 Note that TCP doesn't have a client server concept There are two hosts, each of them able to send and receive Clients and servers only exist in the application layer
Why is the last ACK needed in TCP four way termination The question of why the last ACK is required is just that nay FIN only means that the sender of the FIN is done sending, and it must still be open to receive more segments, and it must resend any unacknowledged segments Each side is a peer (client server is an application concept), and both sides must agree that everything is done
Why is TCP acknowledging all the time? I understand seq ack is used to provide a reliable connection service But it seems that during TCP data transmission the ACK bit is ALWAYS set, as demonstrated in the following picture Suppose A
TCP and Go-Back-N - Network Engineering Stack Exchange 1 TCP :cumulative ack for the last correctively received, in-order seg 2 cumulative and correctly received but out-of-order segs are not individually acked ⇒ TCP sender need only maintain SendBase and NextSeqNum What is the meaning of cumulative ACK? and what is the difference between selective ACK? and why TCP uses the first one?