Tcp Ip Protocol Questions Long
The process of reliable data transfer using TCP's sequence numbers and acknowledgments involves several steps to ensure that data is successfully transmitted and received without errors or loss.
1. Establishing a connection: Before data transfer can begin, a TCP connection needs to be established between the sender and receiver. This is done through a three-way handshake process, where the sender sends a SYN (synchronize) packet to the receiver, the receiver responds with a SYN-ACK (synchronize-acknowledgment) packet, and finally, the sender acknowledges the receiver's response with an ACK packet.
2. Segmenting and numbering data: The data to be transmitted is divided into smaller segments, each with a sequence number assigned to it. The sequence number represents the byte position of the data within the entire stream. This allows the receiver to reassemble the segments in the correct order.
3. Sending and receiving data: The sender starts transmitting the segmented data to the receiver. Each segment is assigned a sequence number and sent over the network. The receiver receives the segments and acknowledges their successful receipt by sending an acknowledgment (ACK) packet back to the sender. The ACK packet contains the next expected sequence number, indicating that all previous segments have been received successfully.
4. Retransmission and timeout: If the sender does not receive an ACK packet within a certain time period (known as the timeout), it assumes that the segment was lost or corrupted during transmission. In such cases, the sender retransmits the segment with the same sequence number. The receiver, upon receiving a duplicate segment, discards it and sends an ACK packet with the next expected sequence number.
5. Flow control: TCP also incorporates flow control mechanisms to prevent the receiver from being overwhelmed with data. The receiver advertises its available buffer space to the sender using a window size value in the ACK packet. The sender adjusts its transmission rate based on this window size, ensuring that it does not overwhelm the receiver's buffer.
6. Reassembly and delivery: The receiver uses the sequence numbers of the received segments to reassemble the data in the correct order. Once all the segments have been received and reassembled, the data is delivered to the receiving application in the correct order.
7. Connection termination: Once all the data has been transmitted and received, the TCP connection is terminated. This is done through a four-way handshake process, where both the sender and receiver exchange FIN (finish) packets to initiate the connection termination. The sender and receiver then acknowledge each other's FIN packets, and finally, the connection is closed.
Overall, the use of sequence numbers and acknowledgments in TCP ensures reliable data transfer by providing mechanisms for error detection, retransmission, flow control, and orderly delivery of data.