Checksum
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error detection method for most TCPIP
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User Datagram Protocol (UDP)
- Connectionless and unreliable communication.
- Faster than TCP.
- Commonly used for transferring small amounts of data.
- Does not guarantee delivery, correct order, or retransmission of lost data.
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Transmission Control Protocol (TCP)
- Connection-oriented and reliable communication.
- Slower than UDP.
- Commonly used for transferring large amounts of data.
- Ensures data is delivered correctly and retransmits lost data when necessary.
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TCP Mechanisms for Reliable Data Transmission
- Sequence Numbers
- Every byte of data is assigned a sequence number.
- Allows the receiver to reorder segments and detect missing data.
- Acknowledgements (ACKs)
- The receiver sends an ACK containing the next expected byte number.
- Confirms that data has been received correctly and in order.
- Retransmission
- The sender starts a retransmission timer for each segment sent.
- If no ACK is received before the timer expires, the segment is resent.
- Detects and recovers from lost segments or ACKs.
- After receiving three duplicate ACKs, TCP can retransmit the missing segment immediately.
- Checksum
- Each TCP segment contains a 16-bit checksum covering its header and data.
- Detects data corruption during transmission.
- A corrupted segment is discarded and treated as lost.
- Flow Control
- The receiver advertises a window size.
- Controls how much data the sender may transmit before receiving an ACK.
- Prevents the receiver’s buffer from overflowing.
- Ordered Delivery
- The receiver temporarily stores segments that arrive out of order.
- Segments are delivered to the application only after they are arranged in the correct sequence.
- Sequence Numbers
