Wednesday, 16 May 2012

Difference between Frame, Packet Segment and Datagrams ?

These terms are used to refer at which OSI layer we are referring to, the data remain same but the headers and trailers are getting added or removed.

In Phy layer i.e. physical layer the actual data is in "bits" i.e. 0 and 1.

When it reaches to data link layer or Layer 2 it becomes "frame" with source and destination mac address getting added.

When it reaches the third layer or the networking layer it becomes a "packet" with source and destination IP address attached to it.

Finally it become "segment" at Layer 4 or TCP/IP layer. Basically "segment" term is used for TCP connections and "datagrams" for UDP.

So what about other layers like : session, presentation and application ? In these layers the data is termed as "PDU" or "protocol data unit".

So when someone says, that a "frame" is being received by a networking device, then you know that the device is switch.

Router receives a packet and process it.


  1. Thank u very much...;)

  2. Thank you it's great notes

  3. This is perfect, so let's take this even further. Now how do we define and group network communications? For instance in a file transfer, what do we call the grouping of frames that make up the entire transfer (or at least a completed portion of the transfer)? Furthermore how does windowing sizes modify this communication and where does standard 1500 byte MTU come into play?

  4. best explanation I've come across. thank you

  5. Many many thanks Sir... Very precise explanation...:-)

  6. thank u very much fr this explanation. its very simple and easy for understanding

  7. This comment has been removed by the author.

  8. Best explanation found on the internet.


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