[Make-wifi-fast] Layering [was: perverse powersave bug with sta/ap mode]

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Thu Apr 28 13:28:23 EDT 2016

> As wifi has evolved all sorts of packets below the conventional link
> layer that are invisible to IP (management frames in general), perhaps
> finding saner ways of exposing these packet types and their properties
> to the conventional IP stack - and the IP stack to the properties of
> the wifi frames - would be of help.

I think it might be useful to think why TCP/IP has eaten all the other
protocol suites for lunch.

TCP/IP is a horribly inefficient protocol suite.  Any on of us could
design something simpler, more elegant, and more efficient.  TCP/IP
wastes precious bits in multiple headers, and wastes opportunities for
optimisation by avoiding to a great extent cross-layer optimisations.

So why did TCP/IP succeed?  Because it is layered.  The price you pay for
layering is the inefficiency, but it is well worth it -- because it is
lower-layer agnostic, TCP/IP was able to adapt to new physical layers
faster than all the other protocols.  If you're not convinced, please try
running DECNET natively over ATM (encapsulating Ethernet frames within
AAL3/4 PVCs doesn't count).

I don't think it's productive to get the network layer know to much about
the details of the physical layer -- all your work will need to be redone
in five years, when the next iteration of .11 breaks your assumptions.
The link layer is where the phy-related smarts belong.

(Now babeld has some knowledge of lower-layer characteristics, and this
causes no end of trouble.  But it's not too bad, since it's just the
implementation -- no lower-layer assumptions reside in the protocol beyond
those made by IP.)

-- Juliusz

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