Layer 3.5 is actually layer 4

[Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>]

Iljitsch;

The fallacy of layer 3.5 is introduced to assert that layer 3
solutions had existed, which is why Brian wrote a sweeping
definition:

> We can hardly disagree. But TCP is not SCTP, UDP, DCCP or ICMP either.
> The systems level argument for a layer 3.5 solution is that it can cover
> all cases, including ones we have not invented yet.

As you modify Brian's definition of layer 3.5 that:

	UDP being a special case 

there will be other special cases for non-TCP protocols including
ones we have not invented yet that there is no reason to insist
on the fallacy.

So, your reduced requirement is merely that:

	The systems level argument for a layer 3.5 solution is
	that it can cover a TCP case.

which is a TCP specific layer 4 solution.

That is, there is no such thing as layer 3 solutions.

Note that layer 4 protocols can and will share some function
calls to control M6, just as TCP and UDP can share a function
call to compute check sum that it is an issue independent of
layering. We don't have to make transport layer check summing
layer 3.5, only to let TCP and UDP share some function calls.

							Masataka Ohta