In this post, we will learn how the TCP (Transmission Control Protocol) works with a real-time example.
TCP is a reliable and connection-oriented protocol that operates at the transport layer of the TCP/IP networking model. Its primary goal is to provide a reliable and ordered delivery of data packets between two network hosts over an IP-based network.
Let's imagine a scenario where you are sending a file from your computer (the client) to a remote server over the internet using a file transfer application. TCP ensures that the file transfer is reliable, and the data arrives intact at the destination.
Here's how the TCP protocol works step-by-step in this Scenario:
1. Establishing a Connection:
- The client initiates a connection request to the server using a three-way handshake. The handshake involves a series of messages between the client and server to establish a connection.
- The client sends a SYN (Synchronize) packet to the server, indicating its intention to establish a connection.
- The server receives the SYN packet and responds with a SYN-ACK (Synchronize-Acknowledge) packet, indicating its agreement to the connection request and its readiness to receive data.
- The client receives the SYN-ACK packet, acknowledges it by sending an ACK (Acknowledge) packet to the server, and completes the connection establishment.
2. Data Transfer:
- Once the connection is established, the client can start sending data packets to the server.
- The client divides the file into smaller chunks called segments and assigns a sequence number to each segment to maintain the order.
- The client sends these segments to the server, which receives and acknowledges the successful receipt of each segment.
3. Flow Control:
- TCP utilizes flow control mechanisms to ensure that the sender does not overwhelm the receiver with data.
- The receiver maintains a receive window that specifies the amount of data it can accept at a given time.
- The sender adjusts its transmission rate based on the receiver's advertised window, ensuring that the data transmission is paced appropriately.
4. Retransmission and Error Handling:
- TCP employs various mechanisms to ensure reliable data delivery.
- If the sender does not receive an acknowledgment for a sent segment within a certain timeout period, it assumes that the segment was lost or damaged.
- The sender retransmits the lost segment, and the receiver acknowledges it upon receipt.
- TCP also uses checksums to detect and discard corrupted data packets.
5. Connection Termination:
- Once the file transfer is complete, the client and server initiate the connection termination process.
- The client sends a FIN (Finish) packet to the server, indicating its intention to close the connection.
- The server acknowledges the FIN packet and sends its own FIN packet to the client.
- The client responds with an acknowledgment, and both ends of the connection are closed.
In summary, TCP ensures reliable and ordered data transmission by establishing a connection, dividing data into segments, handling flow control, retransmitting lost segments, and properly terminating the connection.
By providing these features, TCP guarantees that your file transfer is accurate, complete, and delivered in the correct order, even in the presence of network congestion, errors, or packet loss.
Tags:
network protocol