Instantaneous Threshold ECN marking for DCTCP

Instantaneous Threshold ECN marking for DCTCP

[Bryce Cronkite-Ratcliff]

Hi there,

I am attempting to run some experiments with DCTCP using mininet (so
this is all user-level emulation -- my switch is a linux namespace
using OVS). My question is on how to apply DCTCP's AQM. DCTCP's AQM
just marks all packets with CE if they are received when the queue is
over a threshold value of K and otherwise does not mark CE. The DCTCP
papers I have seen suggest that RED can be used to achieve this: set
probability to 1, burst to 1, and min and max to the same value.

However, tc-red, in accordance with this paper, does not allow burst
to be significantly below the minimum threshold value, so I am unable
to set the parameters I would like -- in particular to set burst to 1
-- without monkey-patching tc.

Is there a way to achieve this simple threshold-ECN marking AQM with
tc, or another approach?

Thank you!

Re: Instantaneous Threshold ECN marking for DCTCP

[Florian Westphal]

Bryce Cronkite-Ratcliff <brycecr@gmail.com> wrote:
> Is there a way to achieve this simple threshold-ECN marking AQM with
> tc, or another approach?

Use codel or fq-codel with 'ce_threshold' added by Eric Dumazet, see

https://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/commit/?id=df1c7d9138eafd5b96e81040b0c1475b6d73d158
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=80ba92fa1a92dea128283f69f55b02242e213650