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  1. Senior Member
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    #1

    Default OSI Layer and DNS

    Does DNS reside on the Session Layer of the OSI model ?

    Please Advise.
    "A lot of fellows nowadays have a B.A., M.D., or Ph.D. Unfortunately, they don't have a J.O.B."

    Fats Domino
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  3. Senior Member
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    #2
    I believe DNS is an Application layer service.
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  4. Questionably Benevolent Moderator Slowhand's Avatar
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    #3
    Yup, I believe it is. DNS isn't "part" of the group of protocols that are modeled with the OSI model, it's a service that runs for the benefit of wetware (that'd be us single-core, easily crashable humans).

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  5. Senior Member
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    #4
    DNS is layer 7 which is the application layer.
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  6. Member
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    #5
    A little tip for DNS

    UDP port 53 for name resolution for clients

    TCP port 53 for zone transfer for secondary (and trinary, if any) DNS server
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  7. Senior Member bighornsheep's Avatar
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    #6
    I thought that DNS was part of TCP/IP suite, but then I thought that TCP/IP suite only spans layers 1-4.

    hmm..I am a little confused...is layer 7 also part of TCP/IP?
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  8. Senior Member
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    #7
    bighornsheep, you're using Meyers' Network+ Passport, right? Check pages 141-142; DNS is an application layer service that uses UDP, which is part of the TCP/IP stack.
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  9. Member
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    #8
    Oh, have I confused you? You are familiar with the OSI 7 layered model, as you know? On ther other hand, TCP/IP 4 layered model doesn't touch any on its application layer: application, presentation, and session layers in OSI, assuming application itself works on.

    So, my understanding is, in terms of application, say, FTP works atop in either OSI or TCP/IP model. In terms of protocol, FTP works in the transport layer, TCP 20 for data flow, 21 for session control.

    Note: HTTP is tricky. HTTP applications work atop but its protocol works in the presentaion layer.
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  10. Member
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    #9
    Oh, have I confused you? You are familiar with the OSI 7 layered model, as you know? On ther other hand, TCP/IP 4 layered model doesn't touch any on its application layer: application, presentation, and session layers in OSI, assuming application itself works on.

    So, my understanding is, in terms of application, say, FTP works atop in either OSI or TCP/IP model. In terms of protocol, FTP works in the transport layer, TCP 20 for data flow, 21 for session control.

    Note: HTTP is tricky. HTTP applications work atop but its protocol works in the presentaion layer.
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  11. Member
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    #10
    Sorry, duplicate post

    Below may help on DNS.

    http://www.soi.wide.ad.jp/soi-asia/p...terials/01.pdf
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  12. Senior Member bighornsheep's Avatar
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    #11
    got it. Thanks Gennosuke HIGAKI, kujayhawk93!
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  13. Senior Member
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    #12
    Thank you all for helping me clear that up. I was at Borders Bookstore yesterdsay and read from a Network Plus book that DNS was mapped to the session Layer of the OSI model.

    Thanks again
    "A lot of fellows nowadays have a B.A., M.D., or Ph.D. Unfortunately, they don't have a J.O.B."

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