"Chipps,Ken" asked,
>What is the source of this information on the sublayers of the layers in the
>OSI model? Is this information that is readily available? Do other layers of
>this model, besides the IEEE defined sublayers of the Data Link layer, have
>sublayers assumed as well? In other words, where can I find more information
>on this topic? I have not seen it in any of the standard texts or I
>overlooked.
The ISO document title is "Internal Organization of the Network
Layer." I don't have my copy near to hand, so can't give you the
number. As with other ISO documents, it is not available free, but
can be downloaded. Other relevant ISO documents include TR 10000 on
functional profiles, the ISO Routeing Framework, and the management
annex to the OSI Reference Model.
I do discuss it in Chapter 4 of my book on "Designing Addressing
Architectures."
Unfortunately, reference models in general are far more important in
teaching and certification contexts than they are to (very rigorous)
protocol designers. To be perfectly honest, I can't think of an IETF
discussion for years that ever really concerned itself with what
layers things belonged in. We are concerned with the abstract
concepts of layering, but there are a lot more recent and relevant
concepts in protocol design than the OSI model.
Just noticing you are with the State of Texas -- if Jerry Johnson
still works in the Division of Information Technology, he worked on
some of these specifications.
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
>Howard C. Berkowitz
>Sent: Wednesday, June 13, 2001 10:55 AM
>To: [EMAIL PROTECTED]
>Subject: Re: ARP and TCP/IP layering [7:8335]
>
>
>>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
>
>
>Lots of books are indeed wrong, when judged against the ISO Internal
>Organization of the Network Layer document. Stripping to a minimum
>of OSI speak, what we think of the network layer actually has three
>sublayers, one of which arguably extends into the data link layer or
>at least overlaps it.
>
>The Subnetwork Independent Convergence Layer is the truly
>link-independent part such as IP or CLNP.
>
>The Subnetwork Access Protocol is the interface to intelligent layer
>2 protocols that have payload identification -- X.25, ATM, LLC, etc.
>
>The Subnetwork Dependent Convergence Facility maps between the
>Subnetwork Independent and Subnetwork Access parts. ARP goes here.
>
>Going a step farther, it's also worth considering the functional as
>well as layering models of B-ISDN/ATM, which identify the U(ser),
>C(ontrol)/signaling and M(anagement) planes at each layer. ARP is a
>C plane protocol between the end host and the ingress relay, much as
>is Q.931 and Q.2931. IP routing protocols, PNNI and SS7 are
>relay-to-relay M plane protocols.
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=8427&t=8335
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