Aha! You are correct, sorry about that. These long threads get to
be unintelligible after a while. On that note, I vote to end it. :-)
>>> "Chuck Larrieu" 6/15/01 1:30:19 PM >>>
I believe the words you are attributing to me were written by Howard.
You
snipped a bunch from the original message, which included my one line
smart
ass remark in response to something Howard had said.
Chuck
-----Original Message-----
From: John Neiberger [mailto:[EMAIL PROTECTED]]
Sent: Friday, June 15, 2001 12:14 PM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]
Subject: RE: ARP and TCP/IP layering [7:8335]
Comments inline....
>>> "Chuck Larrieu" 6/15/01 1:04:26 PM >>>
>At 11:50 AM 6/13/01, John Neiberger wrote:
>>This topic has come up a few times in the past and I don't think we
ever
>>came to a common agreement. Several people made good arguments on
both
>>sides. I don't recall the specific argument, but I believe someone
even
>>made a convincing argument that it was an application layer
function.
>>Perhaps someone here remembers that thread and could refresh our
> >memories.
John, and I think you know I'm not picking on you, people certainly
can argue about things. At the same time, I want to make the
distinction between secondary and primary sources. A secondary
source, in the Cisco context, is something primarily derived from a
course, or other Cisco materials. These materials aren't necessarily
what the Cisco developers would have said.
A primary source is an RFC, or an ISO document, etc., or someone who
was directly involved in the standards or product development. Even
there, there will be conflicts. It is quite common to see people
here referring to the interpretation of IP in RFC 760, 791, etc.,
when these have been superceded by RFC 1812.
JN: Chuck, stop picking on me! :-) First it's the 10baseT and full
duplex issue and now this! Truthfull, I don't know if it's for lack
of
caffeine yet today but I'm not sure I get your point here. I was
simply
trying to diplomatically say that this topic had been covered multiple
times and yet people still disagree on the outcome of those
discussions.
> >
>>When most people think of host-to-host communications they think of
one
>>layer on one device speaking to the corresponding layer of another
>>device. In this case of ARP I personally feel that we have the
network
>>layer of one device speaking to the datalink layer of another. Even
>>that point is a little shaky because at the destination the packet
must
>>reach the network layer to be recognized, but the information
desired
>>from the end station is layer two, not layer three.
>>
>>I would also suggest that we determine the layer at which a function
>>resides by looking at the layer that originated the request for
>>information.
That is generally valid, and, in fact, is a fair description of the
formal OSI concept of service layering as distinct from protocol
layering. The distinction between services and protocols is rarely
taught, mostly because the instructional people think it's too
abstract.
>In this case, it's the desire of the network layer in one
>>device to speak to the network layer of another device that
initiates
>>this entire process. An ARP is generated at the request of the
network
>>layer. This ARP seeks out the destination device, gathers the
necessary
>>information, and delivers that information to the network layer of
the
>>originating device.
>>
>>Because of those two arguments I'd say that the ARP function
overlaps
>>both the network and datalink layer. It is a datalink frame
generated
>>at the request of the network layer, and it just doesn't fit
perfectly
> >into either layer.
No, it's that the datalink and network layers don't fit the necessary
function of ARP. More precisely, the datalink and network layers,
when not split into control and forwarding, are an expecially bad fit.
JN: Your description of the problem fits but I feel that mine is
valid
as well, especially considering Howard's input about Subnetwork
Dependent Convergence Facilities. From his description, if you were
attempt to squeeze ARP into the OSI model, it really would appear to
overlap the two layers since it exists as a sort of service interface
between the two layers.
But, as I qualify a lot of things, I may be wrong. I'm weary from
thinking about it, so stop picking on me.
> >
>>Then again, I may be wrong. :-)
>>
>>Regards,
>>John
>>
>> >>> "Dr Rita Puzmanova" 6/13/01 7:58:53 AM >>>
>>Hi all,
>>
>>Trivial yet fundamental question. I have seen ARP described as part
of
>>the network (internet) layer so many times that I have started to
>>believe it belongs there (although I know well that it operates "as
>>if"
>>the Layer 2 protocol - as per OSI RM). Now I have eventually come
>>across
>>Doug Comer's statement: "It's part of the network interface layer."
>>
>>I should not ask where the truth is but still I will. That would
mean
>>quite a lot of books are incorrect in this (including Cisco
>>materials).
>>
>>Rita
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=8773&t=8335
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