when a connectionless protocol is in use at a lower layer of the OSI model, how is missing data detected and retransmitted if necessary?
When a connectionless protocol is in use at a lower layer of the OSI model, missing data is detected and retransmitted through the use of error detection and retransmission mechanisms.
One common way to detect missing data is through the use of a checksum. Here, a calculated checksum value is sent along with the data. The receiving end also calculates the checksum and compares it with the received checksum value. If the calculated checksum and received checksum do not match, it indicates that there is missing or corrupted data. In this case, the receiver can request retransmission of the missing data.
In some cases, sequence numbers are also used to detect missing data. Each segment of data is assigned a unique sequence number by the sender. The receiver keeps track of the received sequence numbers and checks for any gaps or missing numbers. If a gap is detected, it indicates missing data, and the receiver can request retransmission.
Once missing data is detected, the receiver can request retransmission from the sender. The sender, upon receiving the retransmission request, sends the missing data again. This process continues until the missing data is successfully received by the receiver.
It is important to note that in a connectionless protocol, each message or data segment is treated independently and there is no built-in acknowledgment or acknowledgement of successful transmission. Therefore, it is up to the sender and receiver to implement mechanisms for error detection and retransmission as needed.
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