Re: [Bloat] dslreports bufferbloat tests

[jb <justin@dslr.net>]

thanks

And yes Dave, some logged tests (if we pre-arrange what day, and you
tell me the UTCs) using this particular server would be good, I'll be
in touch on that, I have to setup a capture that just isolates your
IP.

So Is there anything different, or detectable, on the server side for
such a fully congestion aware connection, but no congestion is
encountered?
So on upload phase, I can see CE marks come in, but during download
phase there is nothing interesting to detect and log?

On Wed, Apr 20, 2016 at 10:43 PM, Jonathan Morton <chromatix99@gmail.com> wrote:
>
>> On 20 Apr, 2016, at 09:06, jb <justin@dslr.net> wrote:
>>
>> So this particular snap from the first 200 packets of a download there
>> are poor RTTs but it also picked up the IP ecn_capable flag (but not
>> the IP ecn congestion flag) and it picked up the TCP ece and cwr flags
>> on.
>
> The TCP ECE and CWR flags are always set during ECN negotiation.  If there are no CE marks subsequently, they will not appear again once the data phase begins.  You can therefore distinguish between ECN capability of the host and the network.
>
> For a “download” test, your sender will see ECE flags inbound and generate CWR flags outbound *during the data phase* only if there is an ECN aware AQM on the path at the bottleneck.  It will not see the CE marks themselves, as those are only present between the bottleneck and the receiver.
>
> For an “upload" test, your receiver will see the inbound CE marks from an AQM active on the bottleneck, respond to them with ECE flags, and receive CWR flags in reply.  Again, only during the data phase.
>
>  - Jonathan Morton
>