It's possibly an exercise in bad faith to continually reintroduce written
materials that have been explicitly discounted by people who can make a
legitimate claim to understand the context they were churned out in. In
this case, the cisco materials often don't offer any substantiative
reasoning for their arbitrary taxonomical assignents of protocols as far as
higher-numbered layers of the osi stack are concerned (providing somewhat
of a contrast to their treatment of better-scrutinized layers).
I'm a little concerned though, about the following:
In sentence 7, you place RPC in the session layer. Two sentences earlier,
you cite NFS' "use" of RPC as a justification for assuming that NFS resides
in the session layer. While it might be exactly an example of the
discontinuities you cite in your first paragraph, one of the few
straightforward parts of the out-of-control agglomeration of ideas &
assertions that constitute the concept of osi communications protocol
layering as it appears in (english) print seemed to be the notion that
services maintained at level X+1 "use" services at layers X, and do not
(directly) interact with other X+1 entities. Am I missing something?
In either case, some instances where treatments clash are rife with
potential insight & revelant ambiguities, while others are not. It's not
clear that the certification prep treatments of this abstraction belong in
the former category (most notably for their unignorably light treatment of
upper-layer protocol characteristics), rendering them a dubious
justification for a "reasonable" opportunity to "think otherwise."
I dread the day when all extant statements about a given topic are accorded
equal weight (not least of all because I make statements about given topics
and would find it hard to live with such a weighty burden).
"Carroll Kong" @groupstudy.com on 12/09/2001 04:59:49
PM
Please respond to "Carroll Kong"
Sent by: [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
cc: (bcc: Kevin Cullimore)
Subject: RE: Does session layer protocol use IP address ? [7:28378]
Priscilla, I think you are being a bit too hard on the guy. He
tried to do some real research, he is referencing other written
material. I did some quick research and I am finding some information is
clashing about it. I think sometimes it is hard to make the differentiate
between the layers for certain constructs.
I think perhaps, WHY NFS is so often put in the Session Layer is
because it uses RPC. Also, NFS does do synchronization of files, which can
be heavily argued as a Session Layer characteristic. I would say RPC
definitely is in the Session Layer. NFS does synchronization, (remember
the ancient days of keeping file consistency with UDP?) but looks like it
might be at the application layer. I suppose that is where the confusion
is. And since NFS definitely uses RPC, and there "can only be ONE",
perhaps NFS is truly just at the application layer. You could argue that
it mountd that really allows remote mounting and nfsd just does
synchronization.
I think it is somewhat debatable and reasonable for him to think
otherwise if so many other references point it to the wrong direction.
I am interested in any reference, as that is how we make sure we
did not mislearn something.
At 02:04 PM 12/9/01 -0500, Priscilla Oppenheimer wrote:
>At 06:18 PM 12/8/01, anil wrote:
> >This is from Cisco Oct 2001 Packet..
> >http://www.cisco.com/warp/public/784/packet/oct01/p76-training.html
> >
> >It must be out of date :-)
>
>Not "out of date." Just wrong. You can keep coming up with wrong material.
>What's your point?
>
>Have you looked at NFS with a Sniffer? Have you read a Unix man page? Have
>you checked some RFCs?
>
>Have you considered what NFS does? What are its functions? What do its
>messages look like? What protocols below it does it rely on? What problems
>were its creators trying to solve?
>
>Please stop sending messages about this topic (or any other topic) until
>you have done some real research. In your last message you quoted page 9
of
>a CCNA book. Sorry to burst your bubble, but nobody on this list could
care
>less what it says on page 9 of a CCNA book. This list is for people
>studying for advanced Cisco certifications.
>
>Priscilla
>
> >-Anil
> >------------------------
> >
> >5. Session Layer
> >The session layer provides services in the application to manage
inter-host
> >communication. Think of this function as the old-time telephone
switchboard
> >operator: first, watching for a light on the switchboard indicating a
> >connection was needed, next connecting and monitoring the call, and then
> >finally disconnecting it by pulling the plug. For example, Network File
> >System (NFS) is like an extended feature Telnet program for UNIX that
keeps
> >a connection (session) alive and available until the terminate command
is
> >given. Other examples include Structured Query Language (SQL), Remote
> >Procedure Call (RPC), and X-Windows.
> >
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> >Priscilla Oppenheimer
> >Sent: Saturday, December 08, 2001 3:13 AM
> >To: [EMAIL PROTECTED]
> >Subject: RE: Does session layer protocol use IP address ? [7:28378]
> >
> >
> >That's 40% right.
> >
> >SQL, NFS, and XWindows are application-layer protocols.
> >
> >RPC and NetBIOS are session-layer protocols.
> >
> >We often have discussions about which books are best. Todd Lammle books
can
> >teach you basic router configuration. They are often wrong where
protocol
> >behavior is concerned.
> >
> >A better reference for learning about OSI is the OSI paper by Howard
> >Berkowitz at http://www.certificationzone.com.
> >
> >Priscilla
> >
> >At 11:32 PM 12/7/01, anil wrote:
> > > >The session layer is an elusive beast that is not implemented much
> > >Yes, I checked it out..
> > >Session layer protocols include:
> > >SQL, NFS, RPC, NetBios, Xwindows are examples of session layer
protocols.
> > >Page 9 of CCNA 2nd Edition study guide Todd Lammle
> > >
> > >-Anil
> > >
> > >
> > >
> > >
> > >-----Original Message-----
> > >From: anil [mailto:[EMAIL PROTECTED]]
> > >Sent: Friday, December 07, 2001 11:17 PM
> > >To: Priscilla Oppenheimer; [EMAIL PROTECTED]
> > >Subject: RE: Does session layer protocol use IP address ? [7:28378]
> > >
> > >
> > > >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
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
-Carroll Kong
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