VTU Module - 4 | Transport-Layer Protocols in the Internet

18EC71 | COMPUTER NETWORKS | Module-4 VTU Notes

Transport-Layer Protocols in the Internet: User Datagram Protocol (UDP) and Transmission Control Protocol (TCP)

The transport layer of the Internet is vital for ensuring reliable communication between devices. Two prominent protocols, User Datagram Protocol (UDP) and Transmission Control Protocol (TCP), serve as the backbone for data transmission.

User Datagram Protocol (UDP):

• User Datagram: UDP is a connectionless, lightweight protocol that facilitates quick data transmission. It operates without establishing a connection first, making it suitable for scenarios where speed is crucial.
• UDP Services: Despite its simplicity, UDP offers essential services such as checksums for error detection, port numbers for application identification, and minimal overhead, making it a preferred choice for real-time applications like video streaming and online gaming.
• UDP Applications: Applications that prioritize speed and can tolerate some data loss, such as DNS, Voice over IP (VoIP), and streaming services, often utilize UDP for efficient communication.

Transmission Control Protocol (TCP):

• TCP Services: In contrast to UDP, TCP is a connection-oriented protocol that guarantees reliable and ordered delivery of data. It establishes a connection before data exchange, ensuring that packets arrive intact and in the correct order.
• TCP Features: TCP provides a range of features, including flow control to manage data congestion, error control through acknowledgments and retransmission of lost data, and a sliding window mechanism for optimizing data transfer efficiency.
• Segment and Connection: TCP divides data into segments, each assigned a sequence number to facilitate orderly reconstruction on the receiving end. It establishes a connection using a three-way handshake, ensuring both sender and receiver are ready for data exchange.
• State Transition Diagram: TCP operates in various states, transitioning between them during different phases of communication. These states include CLOSED, LISTEN, SYN SENT, SYN RECEIVED, ESTABLISHED, FIN WAIT, CLOSE WAIT, LAST ACK, TIME WAIT, and others, forming a comprehensive state transition diagram.
• Windows in TCP: TCP employs a sliding window mechanism to manage the flow of data between sender and receiver. This allows for efficient use of network resources, adapting to varying network conditions dynamically.
• Flow Control and Error Control: TCP employs flow control to manage the rate of data transmission, preventing congestion and ensuring optimal performance. Error control mechanisms, including acknowledgments and retransmission, enhance the reliability of data delivery.
• TCP Congestion Control: TCP dynamically adjusts its transmission rate based on network conditions, employing algorithms like Slow Start, Congestion Avoidance, and Fast Recovery to prevent network congestion and maintain stability.

In summary, UDP and TCP play crucial roles in Internet communication, catering to diverse application needs. While UDP prioritizes speed and simplicity, TCP ensures reliability through connection-oriented services and sophisticated features like flow control and error detection. The coexistence of these protocols exemplifies the flexibility of the Internet's transport layer, accommodating a wide range of applications and communication requirements.