Cisco Certified Network Associate Exam | OSI Layer for Damaged Frame

OSI Layer for Damaged Frame

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A receiving host computes the checksum on a frame and determines that the frame is damaged. The frame is then discarded. At which OSI layer did this happen?



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A. B. C. D. E.


The Data Link layer provides the physical transmission of the data and handles error notification, network topology, and flow control. The Data Link layer formats the message into pieces, each called a data frame, and adds a customized header containing the hardware destination and source address. Protocols Data Unit

(PDU) on Datalink layer is called frame. According to this question the frame is damaged and discarded which will happen at the Data Link layer.

The correct answer is D. data link.

The data link layer is responsible for framing data into packets, adding a header and trailer to each packet, and performing error detection and correction. The error detection is achieved through the use of a checksum, which is calculated on the entire packet, including the header and trailer.

When a receiving host receives a packet, it computes the checksum on the packet and compares it to the checksum that was included in the packet. If the checksums do not match, it means that the packet has been corrupted during transmission and is considered damaged.

At this point, the data link layer of the receiving host discards the packet and does not forward it up to the network layer for further processing. The network layer is responsible for routing and delivering packets between different networks, and it relies on the data link layer to ensure that the packets are error-free.

Therefore, the fact that the frame was discarded due to a checksum error indicates that the error occurred at the data link layer, where the checksum was calculated and verified.