[Cerowrt-devel] [Codel] FQ_Codel lwn draft article review

Dave Taht dave.taht at gmail.com
Mon Nov 26 16:19:12 EST 2012

On Mon, Nov 26, 2012 at 10:13 PM, Rick Jones <rick.jones2 at hp.com> wrote:
> On 11/24/2012 08:19 AM, Dave Taht wrote:
>> On Sat, Nov 24, 2012 at 1:07 AM, Toke Høiland-Jørgensen <toke at toke.dk>
>> wrote:
>>> "Paul E. McKenney" <paulmck at linux.vnet.ibm.com> writes:
>>> The UDP ping tests tend to not work so well on a loaded link,
>>> however, since netperf stops sending packets after detecting
>>> (excessive(?)) loss. Which is why you see only see the UDP ping times on
>>> the first part of the graph.
>> Netperf stops UDP_STREAM exchanges after the first lost udp packet.
> The UDP_STREAM test will keep blasting along until the end-of-test timer
> fires.  It is the non-burst-mode UDP_RR test which comes to a halt on the
> first lost datagram.
>> After staring at the tons of data collected over the past year, on
>> wifi, I'm willing to strongly suggest we just drop TCP packets after
>> 500ms in the wifi stack, period, as that exceeds the round trip
>> timeout...
> How does WiFi "know" what the TCP RTO for a given flow happens to be? There
> is no 500 millisecond ceiling on the TCP RTO.

the lightspeed equivalent of 1 and half times around the planet is
enough time to spend inside of one computer.

As for the RTO, you're right... sorta.


But I cannot see any harm in wifi, in simply dropping > 500ms old
packets, in the general case, and a lot of potential good.

> rick jones

Dave Täht

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

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