TCP Connection Establishment || Three Way Handshake || Transport layer || Computer Networks

Summary

This video explains the TCP connection establishment process, which is crucial for data transmission between a client and a server. The connection is set up using a three-way handshake: First, the client sends a SYN segment to the server. Then, the server responds with a SYN-ACK segment, acknowledging the client's request. Finally, the client sends an ACK segment to confirm the connection. Once this handshake is complete, full-duplex communication can begin. The video offers a step-by-step breakdown, making the process clear for those interested in understanding how TCP connections are established before data transfer.

Takeaways

• 😀 TCP is a connection-oriented protocol, requiring a connection to be established before data transfer.
• 😀 The TCP connection establishment process consists of three main stages: connection establishment, data transfer, and termination.
• 😀 TCP uses full-duplex communication, meaning data can be transmitted simultaneously in both directions.
• 😀 The TCP connection establishment is achieved through a process called the **three-way handshake**.
• 😀 In Step 1, the client sends a **SYN** segment to the server to initiate a connection, with a sequence number (e.g., 100).
• 😀 In Step 2, the server acknowledges the client's **SYN** with a **SYN-ACK** segment, including its own sequence number (e.g., 200) and an acknowledgment number (e.g., 101).
• 😀 In Step 3, the client acknowledges the server's **SYN-ACK** with an **ACK** segment, completing the handshake and establishing the connection.
• 😀 The **sequence number** in each segment is used to track the order of data transmission, ensuring reliable delivery.
• 😀 The acknowledgment number in each segment indicates the next expected sequence number, helping maintain synchronization between the client and server.
• 😀 After the three-way handshake is complete, both the client and server are ready to begin data transfer, and the connection can later be terminated as needed.

Q & A

What is TCP and why is it called a connection-oriented protocol?

TCP (Transmission Control Protocol) is a connection-oriented protocol, meaning it requires a connection to be established between the client and server before data can be transmitted. It ensures reliable data transfer through a three-step handshake process.

What are the three main steps in the TCP connection establishment process?

The three main steps in the TCP connection establishment are: 1) The client sends a SYN segment to the server. 2) The server responds with a SYN-ACK segment. 3) The client sends an ACK segment back to the server.

What is a SYN segment, and why is it important in the TCP handshake?

A SYN segment (synchronization segment) is sent by the client to initiate the connection with the server. It indicates that the client wants to establish a connection and begins the handshake process. The SYN segment includes a sequence number to track the data transfer.

What is the significance of the sequence number in the TCP handshake?

The sequence number in TCP is used to keep track of the data being sent and received. It ensures that data is delivered in the correct order. Each segment in the handshake includes a sequence number, which increments as the communication progresses.

What does the server send in response to the client's SYN segment?

In response to the client's SYN segment, the server sends a SYN-ACK segment. This segment serves two purposes: it acknowledges the client's request to establish a connection and sends its own SYN request to the client, indicating that it also wants to establish a connection.

What does the ACK segment from the client indicate?

The ACK segment sent by the client indicates that the client has received the server's SYN-ACK segment and is ready to complete the connection. It also acknowledges the sequence number received from the server.

Why is it called a 'three-way handshake'?

It is called a 'three-way handshake' because the process involves three distinct steps: 1) The client sends a SYN, 2) The server sends a SYN-ACK, and 3) The client sends an ACK to complete the handshake.

What does the acknowledgment number in the server's SYN-ACK segment represent?

The acknowledgment number in the server's SYN-ACK segment represents the next sequence number that the server expects to receive from the client. It is calculated by adding 1 to the sequence number of the client's SYN segment.

How does the sequence number change during the three-way handshake?

The sequence number starts with a random value (e.g., 100) in the client's SYN segment. The server responds with an acknowledgment number that is the client's sequence number plus 1 (e.g., 101). The client then sends back an ACK with its own updated sequence number, completing the handshake.

What happens after the three-way handshake is complete?

After the three-way handshake is complete, the connection is established, and the client and server are ready to exchange data. The data transfer occurs in full-duplex mode, meaning both sides can send and receive data simultaneously.