OSI Layer and DNS

mgmguy1

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

Please Advise.

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