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?
A.
session
B.
transport
C.
network
D.
data link
E.
physical
Explanation:
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.
D: just because Receiver recomputes the checksum and compares it with the received value. If they differ, an error has occurred and the frame is discarded.
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B: transport.
Data link layer just alerts upper-layer protocols that a transmission error has occurred. The frame is discarded on trasport layer.
http://docwiki.cisco.com/wiki/Internetworking_Basics#Open_Systems_Interconnection_Reference_Model
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Wron Henrique,
Frames are only sent and received at layer 2 “Data link”.Layer 2 uses a math method called the CRC. If the CRC of the sending host do not match the CRC of the receiving one, the frame is discarded and the sender will need to submit a new frame.
So correct answer is D
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but, the question is about checksum also, it happens only at Transport layer only
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