Lec-66: TCP connection Establishment and connection Termination | Transport layer

Summary

This video provides a detailed explanation of TCP's connection establishment process through the three-way handshake method. It breaks down the steps where a client and server exchange packets to synchronize and establish a reliable connection. The script covers the roles of sequence numbers, synchronization flags, window sizes, and maximum segment sizes, ensuring the smooth flow of data between client and server. By likening TCP to a telephone call, the video illustrates how connection reliability and flow control are achieved, making it an essential protocol for guaranteed data delivery.

Takeaways

• 😀 TCP ensures reliable data transfer through a process called the three-way handshake.
• 😀 The three-way handshake involves three main steps: SYN, SYN-ACK, and ACK.
• 😀 In TCP communication, one machine acts as the client and the other as the server.
• 😀 The client initiates the handshake by sending a SYN packet with a random sequence number.
• 😀 The server responds with a SYN-ACK packet, acknowledging the client's request and providing its own sequence number.
• 😀 The client sends an ACK packet to confirm the server's response, completing the handshake and establishing the connection.
• 😀 TCP is a full-duplex protocol, meaning both the client and the server can send and receive data simultaneously.
• 😀 Sequence numbers are randomly generated for each connection to track the order of packets and avoid conflicts.
• 😀 The window size, advertised by both the client and server, controls the flow of data by specifying the buffer size.
• 😀 The Maximum Segment Size (MSS) defines the largest size of a data packet that can be sent over the network.
• 😀 The three-way handshake ensures that both parties are ready for data transfer, and that data loss is minimized during the transmission.

Q & A

What is TCP connection establishment and why is it important?

TCP connection establishment refers to the process of setting up a reliable communication channel between two devices before data transmission begins. It ensures that resources like buffer, CPU, and bandwidth are reserved, and guarantees data reliability during communication. This is crucial for applications requiring 100% data transfer reliability, such as web browsing or file transfers.

What is the three-way handshake in TCP?

The three-way handshake is a method used in TCP to establish a reliable connection between a client and a server. It involves three steps: 1) The client sends a SYN (synchronize) message to the server. 2) The server responds with a SYN-ACK (synchronize-acknowledge) message. 3) The client sends an ACK (acknowledge) message back to the server, completing the handshake and establishing the connection.

How does TCP ensure reliability in data transmission?

TCP ensures reliability through its connection-oriented nature, using mechanisms like sequence numbers, acknowledgment of received data, and retransmission of lost or corrupted packets. The three-way handshake establishes these initial settings, and further data communication ensures that every packet is properly acknowledged before being considered successfully transmitted.

What role does the sequence number play in the TCP connection establishment?

The sequence number is crucial for tracking the order of packets during communication. It helps ensure that the data is received in the correct order, even if packets arrive out of sequence. Each side of the connection uses a random sequence number during the handshake, and this number is incremented with each new byte of data sent.

What is the significance of the SYN and ACK flags in the TCP handshake?

The SYN (synchronize) flag is used by the client to initiate the connection, signaling that it wants to synchronize with the server. The ACK (acknowledge) flag is used in both the server's response (SYN-ACK) and the client's final acknowledgment to confirm the receipt of the previous message and ensure the reliable establishment of the connection.

What is the 'window size' in TCP, and why is it important?

The window size in TCP refers to the amount of data (in bytes) that can be sent by the sender and buffered by the receiver without waiting for an acknowledgment. It is a form of flow control, ensuring that the sender doesn't overwhelm the receiver. The client and server communicate their respective window sizes during the handshake.

What does 'MSS' stand for in TCP, and how is it used?

MSS stands for Maximum Segment Size, which defines the maximum size of a single TCP segment that can be sent over the network. It is used to ensure that packets are small enough to fit within the data link layer's limitations, such as Ethernet's maximum frame size of 1500 bytes. The MSS helps optimize the data transmission process.

What is the difference between active open and passive open in TCP?

In TCP, active open refers to the client initiating the connection by sending a SYN packet to the server. Passive open refers to the server, which is constantly listening for incoming connection requests but doesn't initiate the connection itself.

Why are random sequence numbers used in the TCP handshake?

Random sequence numbers are used in the TCP handshake to prevent predictability and to ensure security. If all devices started with the same sequence number, it would be easier for attackers to guess and interfere with the communication. By using random numbers, the connection is more secure and unique.

What happens after the three-way handshake is complete in a TCP connection?

Once the three-way handshake is complete, the connection is fully established, and the client and server can begin transmitting data reliably. After the handshake, the client and server continue to communicate with each other by sending data packets, which are tracked and acknowledged using the sequence numbers and window size for flow control.