Hi, Alex,
> On Dec 17, 2021, at 12:53 AM, Alexandre Petrescu
> <alexandre.petre...@gmail.com> wrote:
>
> Le 15/12/2021 à 19:56, Templin (US), Fred L a écrit :
>> Alex,
>>> A new feature in an ALv2 would be that instead of just a
>>> frag-reassembly from sender to receiver, one would consider
>>> group-degroup of packets too, to reduce overhead. If this too is
>>> not already there in ALs.
>> The adaptation layer is that layer below the network layer but above
>> the data link layer. The group-degroup functions you are referring to
>> would apply at the adaptation layer send-side entry or receive-side
>> exit.
>
> Yes, from a topology perspective that's where 'group-degroup' could sit.
>
> From an ISO layer perspective a 'group-degroup' would probably sit in an
> adaptation layer, below IP and above data link layer.
>
> A 'group-degroup' function can also be seen in the jumbogram software
> mechanism, rather than in the frag-defrag mechanism. The jumbogram
> seems to be in the app layer (ApL?) whereas frag-defrag in the
> adaptation layer (AdL?).
>
> This makes wonder whether a group-degroup function would go into ApL or
> rather in the AdL?
Every function can and may occur at any layer in a layered protocol system.
Aggregation and coalescing (what you’re calling group/degroup) already exists
in Ethernet (grouping small packets to avoid the need for padding for min frame
size artifacts from shared-access MAC mechanisms), TCP (to reduce per-packet
overhead, often buried inside interface drivers), and applications (HTTP).
The idea that layer implies function or that functions uniquely exist at a
single layer is one of the great failures of the original OSI model.
The other being that “layer” is ever an absolute, except for the transmission
layer (i.e., the one where logical bits become physical symbols).
Joe
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