[ih] A comment on the seven layer model

[Jack Haverty]

Recursive is a nice improvement, but I think there's still more complexity.

At Oracle in the 1990s we had customers with a mess of a multiprotocol 
IT environment.  Most of them.  There might be LU6.2 in the mainframe 
managing inventory, SPX/IPX in Accounting, Appletalk in the Graphics 
department, TCP in Engineering on their Vaxen and Sparcs, etc.  All of 
them had a need to get to corporate databases.

Everyone was pretty much committed to standardize on TCP.   But it would 
take a while, and the unruliness of the transition period might kill the 
company.

We followed the lead of TCP and created an internet "above" all of those 
other protocol worlds, mimicking what TCP did to interconnect different 
kinds of physical networks.

All was in software, including an "Interchange" which performed 
functions similar to a gateway or router.  But instead of passing 
datagrams from one type of network to another as data travelled, the 
Interchange passed data from one virtual circuit to another (TCP 
connection, SPX connection, whatever the underlying protocol environment 
provided as a reliable byte-stream.)

You needed a few machines able to use multiple protocols, but such 
connections could be patched together as needed, and changed as they 
progressed.  Accounting, perhaps on Novell's SPX, might use an 
Interchange to a DECNET world, and another Interchange somewhere else 
might connect DECNET to TCP where the database lived.

Of course each of those underlying network world might also be its own 
"internet", e.g., with a "global LAN" connecting together the Accounting 
departments at all the companies sites.  They might even all be using 
the same LANs and circuits, with multiprotocol routers to keep all the 
data moving.  But the PCs in Accounting couldn't talk to the mainframes 
running LU6.2

It worked well enough, and provided a means for a company to 
methodically transition from its melange of multiprotocol network 
technologies into its chosen long-term IT architecture, which was 
increasingly based on TCP.  I think it probably helped TCP supplant all 
those other internet technologies, by providing a way for companies to 
"get from here to there".

Corporations had drunk the TCP KoolAid.  We helped them avoid drowning 
in it while they changed everything.  Configurations might change as 
progress was made towards a full TCP-based environment.

All of this might be running on the same physical network, perhaps of 
Ethernets and cisco multiprotocol routers.  We called this underlying 
service of virtual circuits patched together TNS - Transparent Network 
System IIRC.

Does that fit into the 7-layer, or recursive, models?  Seems like it 
might be a challenge.  I never tried.

Jack Haverty


On 4/22/25 20:28, touch--- via Internet-history wrote:
> Yup - recursive - it's the basis of what I call the Recursive Network Architecture, which is the theory on which the way I taught networking works:
> https://www.strayalpha.com/rna/#:~:text=The%20Recursive%20Network%20Architecture%20(RNA,protocol%20layers%20to%20avoid%20reimplementation.
>
> The approach I use is called a “first principles approach to networking”, which ties together info theory, physics, and recursion…
>
> Joe
> —
> Dr. Joe Touch, temporal epistemologist
> www.strayalpha.com
>
>> On Apr 22, 2025, at 8:15 PM, Brian E Carpenter via Internet-history<internet-history at elists.isoc.org>  wrote:
>>
>> I've always argued that the main defect in the 7-layer model is that
>> it isn't recursive, especially in layers 2-5. Given that it was invented
>> by computer scientists, I'm also still a bit surprised by this defect.
>>
>>     Brian
>> On 23-Apr-25 14:01, touch--- via Internet-history wrote:
>>>> On Apr 22, 2025, at 1:58 PM, Steve Crocker via Internet-history<internet-history at elists.isoc.org>  wrote:
>>>>
>>>> Jack,
>>>>
>>>> I liked your comment, "I gave up long ago on trying to stuff this into a
>>>> 7-layer diagram and explain it.”
>>> I like it as well. My class approach is that layers are all relative, e.g., IP-a over IP-b means that IP-a is a transport over IP-b, and IP-b is a link to IP-a.
>>> There’s real utility in layering and in the relation of layers, but not in any absolute count.
>>> Joe
>>> —
>>> Dr. Joe Touch, temporal epistemologist
>>> www.strayalpha.com
>> -- 
>> Internet-history mailing list
>> Internet-history at elists.isoc.org
>> https://elists.isoc.org/mailman/listinfo/internet-history

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