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+28 votes

The protocol data unit (PDU) for the application layer in the Internet stack is:

  1. Segment
  2. Datagram
  3. Message
  4. Frame
in Computer Networks by
edited by | 6.7k views

8 Answers

+60 votes
Best answer

(C) Message is the answer.

For Application, Presentation and Session layers, the PDU is message

For Transport layer, PDU is segment for TCP and datagram for UDP

For Network layer, PDU is packet

For Datalink layer, PDU is frames

For physical layer, PDU is stream of bits

edited by
The answer is Message but I have a doubt. If datagram is related to UDP datagram or IP datagram?
I think datagram is pdu of network layer and not Transport layer, as read from kurose and ross 6th edition pg 51. Why is it that there are so many upvotes for this answer? Am I missing something??
The datagram is PDU at the transport layer. When UDP protocol is used at transport layer, a unit is called as a datagram in the connection-less transfer (while a unit is called as a segment in case of TCP).

Packet is the PDU at Network layer.
+6 votes
PDU for the presentation layer is messages.

PDU for transport layer is segment.

PDU for network layer is packet or datagram.

PDU for datalink layer is frame .

PDU for physical layer are bit streams .
+5 votes
In Netwok layer PDU is called as Datagram.

In transport layer ,PDU is called as Segment.

Whereas In the application layer the PDU is called as the Message.
+2 votes
PDU for application layer is message.
 For transport layer is segment.
  For network layer is packet or datagram.
   For datalink layer is frame and for physical layer is bit streams.
+1 vote



Segment Transport Layer
Datagram Transport Layer
Message Application Layer
Frame  Data Link Layer


0 votes
0 votes
message is the correct at application layer the user directly abble open it and use it
–1 vote
appropiate answer is c
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