[Cerowrt-devel] Problems testing sqm

David P. Reed dpreed at reed.com
Fri Oct 23 18:53:09 EDT 2015

In particular,  the DUT should probably have no more than 2 packets of outbound queueing given the very small RTT. 2xRTT is the most buffering you want in the loop.

On Oct 23, 2015, Richard Smith <smithbone at gmail.com> wrote:
>On 10/23/2015 02:41 PM, Michael Richardson wrote:
>> Richard Smith <smithbone at gmail.com> wrote:
>>      > My test setup:
>>      > Laptop<--1000BaseT-->DUT<--1000baseT-->Server
>> So, given that the DUT is the only real constraint in the network,
>> do you expect to see from this setup?
>> Given that the probably DUT can't forward at Gb/s, and it certainly
>> shape anything, it's gonna drop packets, and it's probably gonna drop
>them in
>> Rx, having overrun the Rx-queue (so tail-drop).  If there is too much
>> (bufferbloated), then you'll see different results...
>Setting ingress/egress to 10Mbit/s I expected to see the speed 
>measurements bounce around those limits with the ping times staying in 
>the low double digits of ms.  What I saw however, was the data rates 
>going well past 10Mbit limit and pings up to 2000 ms.
>This is what I've seen in prior rrul testing using a the 50/10 cable 
>link at our office and my 25(ish)/6 link at my apartment and a well 
>connected server on the net.  That however was using QoS and not SQM.
>Its that a reasonable expectation?

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