The Netacad course material now lists NFS as an Application Layer protocol.
Prof. Tom Lisa, CCAI Community College of Southern Nevada Cisco Regional Networking Academy Priscilla Oppenheimer wrote: > NFS is not a session-layer protocol. Cisco said it was in some early > courseware and the mistake has lived on. The mistake is still in some CCNA > and Cisco Networking Academy materials, I think, but it's wrong. > > NFS is clearly an application-layer protocol. It uses XDR at the > presentation layer. It runs above RPC which is a session-layer protocol. > RPC runs above UDP, which runs above IP. Here was a perfect chance to show > an actual 7-layer protocol stack and Cisco blew it! ;-) > > NetBIOS is a session-layer protocol, as I said in the message. Did you read > it? > > SQL does application-layer stuff, like reading from databases. In an Oracle > environment, it uses the Transparent Network Substrate (TNS) which has > session-layer-like behavior. TNS can run above a variety of protocol > stacks, including TCP/IP, IPX, etc. Cisco texts ignore TNS. I think they > call SQL a session-layer protocol. > > Priscilla > > At 06:15 PM 12/7/01, anil wrote: > > >The session layer is an elusive beast that is not implemented much > >Wait a sec, I thought SQL, NFS and netbios were session layer protocols? > >Someone please correct me. > >-Anil > > > > > >-----Original Message----- > >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > >Priscilla Oppenheimer > >Sent: Friday, December 07, 2001 9:55 PM > >To: [EMAIL PROTECTED] > >Subject: Re: Does session layer protocol use IP address ? [7:28378] > > > > > >At 02:59 AM 12/7/01, mlh wrote: > > >Hi, there, > > > > > >I read Todd Lammle's CCNA2.0 study guide and found this sentence: > "Remember > > >that none of the upper > > >layers know anything about networking or network addresses." I am > wondering > > >if the session layer doesn't > > >use network address, how can it establish a dialogue with other session > > >layer in other host? > > > >I would probably disagree with Todd's statement, although it's taken out of > >context and you haven't given us enough information to say that the > >statement is definitely "wrong." > > > >However, try to picture the numerous OSI pictures you have seen. Most of > >them show horizontal lines between a layer on one host talking to the same > >layer on another host. So the session layer talks to the session layer on > >the other host. That's probably what Todd was getting at. > > > >However, the pictures also show vertical lines. A layer calls on a layer > >below to provide services. Each layer offers services to layers above it. > > > >The session layer is an elusive beast that is not implemented much. But one > >example might help. NetBIOS is a session layer. On a Windows client, when > >you access a Server Message Block (SMB) server, NetBIOS has the job of > >setting up a session with the server. Before it can do that, however, it > >must find the address of the server. If it's a modern Windows network, then > >SMB and NetBIOS are probably running above TCP/IP and UDP/IP. So NetBIOS > >sends a DNS or WINS query to find the IP address of the named server. It > >then sets up a NetBIOS session with the server. Actually, first, the client > >sets up a TCP connection. TCP has port numbers. The client sends to the > >well-known TCP port for NetBIOS session (139) and use an ephemeral port on > >its side. These port numbers could be considered "addresses" at the > >transport layer. > > > >Anyway, back to the question. The statement is at best over-simplified. I > >recommend you get yourself a sniffer and watch what really happens between > >layers. (Ethereal is free by the way.) > > > >Priscilla > > > > > > > > >Thank you for your time. > > > > > >mlh > >________________________ > > > >Priscilla Oppenheimer > >http://www.priscilla.com > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=28510&t=28378 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
