101 · Question #599
Which protocol data unit (PDU) is associated with the OSI model's Physical layer?
The correct answer is D. Bit. The OSI Physical layer's protocol data unit is the bit - the raw binary signal transmitted over a physical medium.
Question
Which protocol data unit (PDU) is associated with the OSI model's Physical layer?
Options
- AFrame
- BDatagram
- CSegment
- DBit
How the community answered
(19 responses)- B5% (1)
- C5% (1)
- D89% (17)
Why each option
The OSI Physical layer's protocol data unit is the bit - the raw binary signal transmitted over a physical medium.
A frame is the PDU of the Data Link layer (Layer 2), which adds MAC addressing and error detection to raw bits.
A datagram is the PDU associated with the Network layer (Layer 3), specifically used by connectionless protocols such as IP.
A segment is the PDU of the Transport layer (Layer 4), used by TCP to provide reliable, ordered data delivery.
The Physical layer (Layer 1) is responsible for transmitting raw binary data as electrical signals, light pulses, or radio waves across a physical medium. The PDU at this layer is the bit, representing the fundamental unit of data - a 1 or 0 - before any logical structure is imposed by higher layers.
Concept tested: OSI model PDU identification per layer
Source: https://www.cisco.com/c/en/us/support/docs/ip/routing-information-protocol-rip/13769-5.html
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