TCP Handshake

TCP Handshake is a process of establishing a connection between two devices over the internet. It is a fundamental concept of the Transmission Control Protocol (TCP), which is a widely used protocol for data transmission across the internet. The handshake involves a series of synchronous steps that help the devices establish a reliable and secure connection before data transfer can occur.

Purpose of TCP Handshake

The purpose of the TCP Handshake is to ensure that the sending and receiving devices are ready to transmit data without any loss or corruption. The handshake process establishes a reliable and secure connection between the devices, allowing the data to be transmitted with guaranteed delivery in the correct order. This process is crucial for applications that require high levels of reliability, such as online banking, e-commerce, and data transfer between servers.

Usage of TCP Handshake

The TCP Handshake is a vital process used in many applications, including web browsing, email, file transfer, and online gaming. Essentially, any application that requires the transmission of data over the internet relies on the TCP handshake to establish a reliable and secure connection.

When a user initiates a connection to a website, for example, the browser sends a SYN (synchronize) packet to the server to initiate the handshake process. The server then responds with a SYN-ACK (synchronize-acknowledge) packet to acknowledge the request and establish the connection. Finally, the client sends an ACK (acknowledge) packet to confirm the connection and start data transmission.

Step-by-Step of TCP Handshake

The TCP handshake process involves a series of steps that occur in a specific order. The following is a detailed breakdown of each step in the handshake process:

1. Step 1: SYN

The first step in the TCP handshake process begins with the client sending a SYN (synchronize) packet to the server. This packet contains a random sequence number that is used to identify the data packets being sent. The SYN packet indicates that the client is requesting a connection with the server.

2. Step 2: SYN-ACK

After receiving the SYN packet, the server responds with a SYN-ACK (synchronize-acknowledge) packet. This packet contains an acknowledgment number that is set to one more than the initial sequence number sent by the client. The SYN-ACK packet indicates that the server is willing to establish a connection with the client and acknowledges the client’s SYN packet.

3. Step 3: ACK

The final step in the handshake process is for the client to send an ACK (acknowledge) packet to the server. This packet contains the acknowledgment number sent by the server in the SYN-ACK packet. The ACK packet confirms that the client has received the SYN-ACK packet, and the connection is established.

TCP Handshake in Action

To better understand the TCP handshake process, let’s take a look at a practical example of how it works. Suppose that a user wants to visit a website hosted on a remote server. The following is a step-by-step breakdown of the TCP Handshake process:

1. Step 1: SYN Packet

The user types the URL of the website they want to visit in their browser’s address bar and presses enter. The browser then sends a SYN packet to the server requesting a connection.

2. Step 2: SYN-ACK Packet

The server receives the SYN packet and responds with a SYN-ACK packet. The SYN-ACK packet contains an acknowledgment number, which is set to one more than the sequence number sent by the client.

3. Step 3: ACK Packet

The client receives the SYN-ACK packet and sends an ACK packet to the server. The ACK packet contains the acknowledgment number sent by the server in the SYN-ACK packet.

4. Data Transmission

With the connection established, the client and server can now begin transmitting data. The client sends an HTTP request to the server, and the server responds with an HTTP response containing the requested webpage.

5. Connection Termination

After the data transmission is complete, the connection is terminated. The client sends a FIN (finish) packet to the server, indicating that it has finished sending data. The server responds with an ACK packet to acknowledge the FIN packet, and the connection is closed.