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Hello Folks! CCNA Layer Question

Discussion in 'General Cisco Certifications' started by Crazydave1990, Mar 15, 2012.

  1. Crazydave1990

    Crazydave1990 Bit Poster

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    Alright guys, new to this forum, but I plan on using it quite often whilst I familiarise myself with Cisco.

    Ok, my question is probably quite simple, however, I'm currently reading a CCNA Book, Cisco Official Cert Guide - CCNA ICND1 640-822 Third Edition.

    Ok, I understand the Application layer basically gathers the info about what the information you require to use you chosen app (like html for example) and makes a request for that data, I understand the transport layer helps prevent data loss by having a error handling protocol, I understand the internet layer is the layer which deals with the I.P's, I understand that the Network Access layer helps decipher what is going to be needed to send/recieve this data, and that the physical later is the actual data transfer...

    but after the transport layer, what protocols are used to prevent data loss? I understand that the bottom layer for example is Application, and the next layer up is transport, and that each layer will always help the preceeding layer (I believe) So application is aided by transport, transport by internet, but is the transport layer responsible for the entire sequence through to finish? or does it only help application?

    thanks for any and all advice folks! peace out! :D
     
  2. soundian

    soundian Gigabyte Poster

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    It takes some time to get your head round the Cisco layers. Try looking at the OSI model, it has a couple more stages than the Cisco model which might help you understand a little better.

    One thing to note: there is no one layer responsible for the whole thing. They all have (fairly) specific tasks to do and recognising which layer the error has occurred in can often be invaluable in troubleshooting issues.
     
    Certifications: A+, N+,MCDST,MCTS(680), MCP(270, 271, 272), ITILv3F, CCENT
    WIP: Knuckling down at my new job
  3. Crazydave1990

    Crazydave1990 Bit Poster

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    Hey man, thanks for the reply, I looked at the OSI model last night, and tbh, it did clarify alot for me, however, I have a query, in the book I have, it basically states the layers in the following order -

    Application
    Transport
    Internet
    Data Link
    Physical

    am I right in saying the Physical is the first stage, then the data link, then internet, so-on and so-forth...?
     
  4. soundian

    soundian Gigabyte Poster

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    Which is the first stage depends on whether your are requesting or serving the data. I think the physical layer is normally designated the first layer, which makes sense from a troubleshooting perspective (Is it plugged in?)
     
    Certifications: A+, N+,MCDST,MCTS(680), MCP(270, 271, 272), ITILv3F, CCENT
    WIP: Knuckling down at my new job

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