[Cake] cake/tc - removal of atm/ptm/ethernet specific overhead keywords
kevin at darbyshire-bryant.me.uk
Thu Jun 2 05:37:22 EDT 2016
In a bid to create yet another day of cake controversy, here's my latest
pull request https://github.com/dtaht/tc-adv/pull/12
It removes all the atm/ptm/ethernet specific overhead keywords.
I find myself largely in agreement with Sebastian where he said:
I would prefer very much if we could just rip the keywords out and just
leave “overhead N” in there. As is the keywords are inconsistent in that
some act as modifiers that “add” to already specified values while
others replace older values whole-sale. Also these keywords do not
really simplify the challenges in choosing the correct overhead at all,
so my vote would be to go from today’s:
[ atm | noatm* ] [ overhead N | conservative | raw* ]
[ atm | noatm* ] [ overhead N | raw* ]
So, instead of documenting the keywords, remove even more (and add an
info/error message to tc to warn users still using the old ones). If
that is not acceptable then I would propose to simply create named
keywords for the individual components that make up the overhead and
apply these in an additive fashion, like:
ppp pppoe ethernet llc snap atmpad aal5sar
which would translate into:
2 + 6 + 14 + 3 + 5 + 2 + 8 = 40
So, I propose to just take the components and their names from
and ad vlan, mac, and fcs to the mix (and maybe the effective additional
overhead required to shape ethernet, IFG and friends).
But honestly I believe we would be better off by directing users to
decent information how to deduce the applicable overhead in each
individual case. Say the link above and maybe a link to
https://github.com/moeller0/ATM_overhead_detector might be of more help
than trying to simply a complex situation?
While at it, I also would remove the “conservative” keyword since with
that we make a promise to our users we might not be able to keep as we
have no guarantee of a maximum overhead possible.
I agree that pointing people to decent info and/or having a small table
in the cake man page with the same info as the now dropped overhead
commands would be far better. My concession is to keep the conservative
keyword. For people who are unwilling to go into this (and I expect
those same people would not be interested in Sebastian's ppp pppoe
ethernet llc....' keyword set) it is *likely* that the addition of a
whole ATM user cell is going to cover the overhead.
I'd be sort of interested to know if anyone is actually using those
keywords: ipoa-vcmux, ipoa-llcsnap, bridged-vcmux, bridged-llcsnap,
ppoa-vcmux, pppoa-llc, pppoe-vcmux, pppoe-llcsnap, pppoe-ptm,
bridged-ptm, via-ethernet, ether-phy, ether-all, ether-fcs, ether-vlan.
How many actually knew they even existed?
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