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Date: Wed, 29 May 2013 15:13:30 +0200
From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Stephen Hemminger <stephen@networkplumber.org>, Eric Dumazet
	<eric.dumazet@gmail.com>,
	David Miller <davem@redhat.com>, j.vimal@gmail.com,
	Michal Soltys <soltys@ziu.info>, Mike Frysinger <vapier@gentoo.org>,
	Jussi Kivilinna <jussi.kivilinna@mbnet.fi>, Patrick
	McHardy <kaber@trash.net>, Jiri Pirko <jpirko@redhat.com>
Message-ID: <20130529151330.22c5c89e@redhat.com>
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	bloat@lists.bufferbloat.net, Jiri Benc <jbenc@redhat.com>,
	Felix Fietkau <nbd@nbd.name>
Subject: [Bloat] tc linklayer ADSL calc broken after commit 56b765b79 (htb:
 improved accuracy at high rates)
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I recently discovered that the (traffic control) tc linklayer
calculations for ATM/ADSL have been broken by:
 commit 56b765b79 (htb: improved accuracy at high rates).

Thus, people shaping on ADSL links, using e.g.:
 tc class add ... htb rate X ceil Y linklayer atm overhead 10

Will no-longer get ATM cell tax/overhead adjusted.

How can we solve/fix this?
Perhaps we can change to use the "stab" system instead (as it does
not seem to be broken by the commit).

But how do we facilitate a change to use "stab" system (for all the
scripts using the old option)?

Can we change the iproute2/tc command to handle this transparently, or
should we give an error/warning if someone uses "tc" and "linklayer" on
a kernel above v.3.8. ?


History:
 - My linklayer ATM changes appeared in kernel 2.6.24 (and iproute2 2.6.25)
 - The STAB changes appeared in kernel 2.6.27

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer