[e2e] Lost Layer?

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed Feb 12 07:03:34 PST 2014

Just saw a reference to this in a later message, I'd missed it:

    > From: "Fred Baker (fred)" <fred at cisco.com>

    > we have at least three common sub-layers within the network layer. One
    > is what we call the Internetwork Layer and should be called, perhaps,
    > the Inter-network sub-layer. It provides the end to end datagram
    > service that TCP and other transports ride atop. Another might .. be
    > called the Intra-network sublayer. It connects systems that are not
    > necessarily directly connected, but use the same technology and are
    > operated by a common administration. .. MPLS, ATM, Frame Relay, and
    > X.25 are all examples of Intra-network protocols. And then there is
    > what one might call the virtualization sublayer, which is when,
    > whatever we call it, we use an IP tunnel between the Internetwork and
    > Intranetwork layers. Static IP/IP and GRE/IP tunnels, LISP, Mobile IP,
    > L2TP, ...

Not sure about everthing in that last list, but for things like ILNP and LISP
(and maybe HIP too) it's actually a shim layer between what you call the
internetwork sub-layer and the _transport_ layer above, not the layer below.

The reason is that things like ILNP and LISP attempt to provide persistent
names for use by the transport layer, ones which is not affected by i) change
of internetwork sub-layer names (i.e. addresses), ii) use of multiple
internetwork sub-layer names, etc. I.e. they are directly below the transport

    > From: John Day <jeanjour at comcast.net>

    > Actually, you weren't using the ISO names. ISO refined its concept of
    > network layer in 8648. 

Perhaps, but the fact remains that the original 7-layer ISO model was a poor
match to the Internet, because the ISO model had too few layers on the lower
end, and too many on the upper - at least, to model the Internet well.

(Although, as someone pointed out, now that we have HTTP/HTML/etc the upper
layers are better matched.)


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