Deciding if the received packet is valid or not valid [closed]

1. What will happen if the packet is not acknowledged?
2. What happens if packets are received out of order?
3. What is the process expected to happen if the sent packets are not reached at the receiver side?
4. Can packets be received out of order?

What will happen if the packet is not acknowledged?

After sending a packet of data, the sender will start a retransmission timer of variable length. If it does not receive an acknowledgment before the timer expires, the sender will assume the segment has been lost and will retransmit it.

What happens if packets are received out of order?

If too many packets are received out of order, TCP will cause a retransmission of packets similar to what happens with dropped packets. As such, the impact of out of order packets on goodput is similar to the impact of packet loss.

What is the process expected to happen if the sent packets are not reached at the receiver side?

The receiver process keeps track of the sequence number of the earliest packet it has not received, and sends that number with every ACK it sends. If a packet from the sender does not reach the receiver, the sender continues to send subsequent packets until it has emptied its window.

Can packets be received out of order?

Packets can arrive out of order. That can happen especially if two packets follow different paths to the destination. Packets can be corrupted, which means that for some reason, the received data no longer matches the originally sent data.