TCP and UDP: Reliability Comparison

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TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are both transport layer protocols in the OSI (Open Systems Interconnection) model. They are responsible for the delivery of data between applications running on different hosts.

TCP and UDP differ in the way they provide reliability for delivery of packets.

TCP provides reliable delivery of packets through error detection, acknowledgment, and retransmission of lost packets. When TCP sends data, it breaks it down into segments, adds a sequence number to each segment, and sends them one at a time. The receiver sends an acknowledgment message back to the sender for each segment received, and if the sender does not receive an acknowledgment, it will retransmit that segment until it is acknowledged. TCP also uses flow control to ensure that the sender does not overwhelm the receiver by sending too many packets at once. This helps to prevent congestion and packet loss.

On the other hand, UDP provides unreliable delivery of packets. When UDP sends data, it breaks it down into datagrams and sends them without checking if they are received by the receiver. UDP does not have any error detection, acknowledgment, or retransmission mechanisms. This means that if a datagram is lost during transmission, it will not be retransmitted, and the receiver will not know that it was lost. However, UDP is useful in applications that do not require reliable delivery of packets, such as real-time video and audio streaming.

In summary, TCP provides reliable delivery of packets through error detection, acknowledgment, and retransmission, while UDP provides unreliable delivery of packets without any error detection or retransmission mechanisms.