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Network+
OSI Layer and DNS
mgmguy1
Does DNS reside on the Session Layer of the OSI model ?
Please Advise.
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Comments
kujayhawk93
I believe DNS is an Application layer service.
Slowhand
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).
Olajuwon
DNS is layer 7 which is the application layer.
Gennosuke HIGAKI
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
bighornsheep
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?
kujayhawk93
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.
Gennosuke HIGAKI
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.
Gennosuke HIGAKI
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.
Gennosuke HIGAKI
Sorry, duplicate post
Below may help on DNS.
http://www.soi.wide.ad.jp/soi-asia/pkg2/materials/01.pdf
bighornsheep
got it. Thanks Gennosuke HIGAKI, kujayhawk93!
mgmguy1
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
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