Hi Jonathan,
> On Jun 5, 2018, at 17:10, Jonathan Foulkes <j...@jonathanfoulkes.com> wrote:
>
> Jonathan, in the past the recommendation was for NOECN on egress if capacity
> <4Mbps. Is that still the case in light of this?
>
> Thanks,
>
> Jonathan Foulkes
>
>> On Jun 4, 2018, at 5:36 PM, Jonathan Morton <chromati...@gmail.com> wrote:
>>
>>> On 4 Jun, 2018, at 9:22 pm, Jonas Mårtensson <martensson.jo...@gmail.com>
>>> wrote:
>>>
>>> Speaking about systemd defaults, they just enabled ecn for outgoing
>>> connections:
>>
>> That is also good news. With Apple *and* Ubuntu using it by default, we
>> should finally get critical mass of ECN traffic and any remaining blackholes
>> fixed, making it easy for everyone else to justify turning it on as well.
The rationale for that decision still is valid, at low bandwidth every
opportunity to send a packet matters and every packet being transferred will
increase the queued packets delay by its serialization delay. The question IMHO
is more is 4 Mbps a reasonable threshold to disable ECN or not.
Here are the serialization delays for a few selected bandwidths:
1000*(1538*8)/(500*1000) = 24.61 ms
1000*(1538*8)/(1000*1000) = 12.30 ms
1000*(1538*8)/(2000*1000) = 6.15 ms
1000*(1538*8)/(4000*1000) = 3.08 ms
1000*(1538*8)/(8000*1000) = 1.54 ms
1000*(1538*8)/(10000*1000) = 1.23 ms
1000*(1538*8)/(12000*1000) = 1.03 ms
Personally, I guess I sort of agree with the <= 4Mbps threshold, maybe 2Mbps,
but at <=1Mbps the serialization delay gets painful.
In sqm-scripts we currently unconditionally default to egress(ECN) off, which
might be to pessimistic about the usual egress bandwidths.
Best Regards
>>
>> - Jonathan Morton
>>
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