[Bloat] AQM creeping into L2 equipment

[Dave Taht]

well on the default load, it looks like you want the mls commands

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/software/release/12-2_37_ey/command/reference/cr.pdf

I imagine with the new tcp's pfifo_fast is going to be sub 8ms also.

however what we are probably seeing with the measurement flows is
slow start causing a whole bunch of packets to be lost in a bunch.

Is your hardware fast enough to run tcpdump -s 128 -w whatever.cap -i
your interface during an entire rrul test without dropping packets?
(on client
and server)



On Thu, Mar 20, 2014 at 9:44 AM, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> Dave Taht <dave.taht at gmail.com> writes:
>
>> I find it puzzling that you still lose the measurement flows early on.
>> Setting some QoS on via WTD might be interesting.
>
> Well if you can be more specific, I'll be happy to. Was looking for a
> way to have per-protocol QoS settings, but there does not seem to be any
> From the documentation (only IP-based).
>
>> If you have a later OS than 3.13 on the sources/sinks you might want
>> to try sch_fq (and sch_pfifo_fast for reference) - the improvements to
>> Linux's TCP are such that on a short path like this that the control
>> loop stays very tight - only two TSO offloads per flow, really
>> accurate use of tcp timestamps, etc.
>
> Added a result set with sch_fq in place of fq_codel to the bottom of the
> same page. Doesn't appear to make much of a difference...
>
>> See also if you have hardware flow control enabled (via ethtool)
>
> If by that you mean pause frames, ethtool seems to think not:
>
> Settings for eth2:
>         Supported ports: [ TP ]
>         Supported link modes:   10baseT/Half 10baseT/Full
>                                 100baseT/Half 100baseT/Full
>                                 1000baseT/Full
>         Supported pause frame use: No
>         Supports auto-negotiation: Yes
>         Advertised link modes:  10baseT/Half 10baseT/Full
>                                 100baseT/Half 100baseT/Full
>                                 1000baseT/Full
>         Advertised pause frame use: No
>         Advertised auto-negotiation: Yes
>         Speed: 1000Mb/s
>         Duplex: Full
>         Port: Twisted Pair
>         PHYAD: 1
>         Transceiver: internal
>         Auto-negotiation: on
>         MDI-X: off
>         Supports Wake-on: d
>         Wake-on: d
>         Current message level: 0x00000007 (7)
>                                drv probe link
>         Link detected: yes
>
>
> -Toke



-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html