10 Replies to “Understanding OSI”

  1. I am confused so the transport takes care of the transport using udp or tcp protocol. With the example of port 80 it knows it needs to go thru the webserver. It adds a header

    The network makes sure it know it route by adding an source and destination ip. Adds it as a header

    Together they make sure the data is send to the right location?

    The data link makes sure it is in the right lan segment adding another header and a trailer correcting errors?
    Because it may hop from router to router the mac adress can change but the ip stays the same?

    Is this correct i know there is more to it. But i typed only the parts that i wanted to make sure was correct.

    Also in the quiz question 2
    Transport is linked to delivering data error free.
    Is it because of the protocols transport uses?
    I thought that in data link it would correct errors?

    1. What you’ve said is correct. Each layer (2-4) add their own headers, and they each have a specific job to do.
      Layer 2 gets the frame delivered from hop to hop
      Layer 3 gets the packet delivered to the right network, and the right host
      Layer 4 gets the segment delivered to the right application

      At layer 2, errors can be detected, causing bad frames to be dropped
      At layer 4, if TCP is used, the receiver can request that the sender resend the missing data

      Does that help?

    1. Hi, same here! I’ve subscribed to the 4$ plan and allowed the networkdirection.net to access my Patreon account but I still receive the message that ‘to view this content, you must be a member of Network’s Patreon at or higher tier’.

  2. I am kind of confused here….

    The Session layer only handles communications within the originator’s machine, right? Like from the Web Browser to the Network Manager? And that could be said kind of like… The Session Layer is the Web Browser and then the Network Manager is the Transport layer? Because the layers can only communicate witheither the one above or the one below, correct?

    When the Transport layer gets a picture file, for instance, from the Session layer it then chops the image file into chunks and on each chunk is added the port # needed on the receiving machine, right?? And then that is sent to the Network layer, but how does the Network layer know what IP address is needed to be listed in the header next? Where does that information come from??

    If you could help me understand that better I have a few questions that I would appreciate help with also, if these answers don’t clear them up… Sorry if I am bothering you, but I really appreciate your time.. Thanks!

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