[Flent-users] [tohojo/flent] packet loss stats (#106)

Toke Høiland-Jørgensen notifications at github.com
Mon Nov 20 15:21:16 EET 2017


Pete Heist <notifications at github.com> writes:

>> On Nov 20, 2017, at 1:11 PM, Toke Høiland-Jørgensen <notifications at github.com> wrote:
>> 
>> Pete Heist <notifications at github.com> writes:
>> 
>> > G.711 can be simulated today with `-i 20ms -l 172 -fill rand
>> > -fillall`. I do this test pretty often, and I think it would be a good
>> > default voip test.
>> 
>> The problem with this is that it also changes the sampling rate. I don't
>> necessarily want to plot the latency every 20ms, so I'd have to
>> compensate for that in the Flent plotter somehow. Also, a better way to
>> deal with loss would be needed.
>
>
> I wondered if/when this would come up… Why not plot the latency every
> 20ms, too dense?

For the current plot type (where data points are connected by lines),
certainly. It would probably be possible to plot denser data sets by a
point cloud type plot, but that would make denser data series harder to
read.

> I guess even if not, eventually at a low enough interval the round
> trip and plotting intervals would need to be decoupled, no matter what
> plot type is used.

Yeah, exactly.

> If we want to minimize flent changes, irtt could optionally produce a
> `round_trip_snapshots` (name TBD) array in the json with elements
> created at a specified interval (`-si duration` or similar) that would
> summarize the data from multiple round trips. For each snapshot, there
> would be no timestamps, but the start and end seqnos would be there
> (if needed), mean delays and ipdv, counts (or percentages?) of lost,
> lost_up or lost_down, etc. I’d need to spec this out, but would
> something like this help?

Hmm, seeing as we probably want to keep all the data points in the Flent
data file anyway, I think we might as well do the sub-sampling in Flent.
Just thinning the plots is a few lines of numpy code; just need to
figure out a good place to apply it.

Handling loss is another matter, but one that I need to deal with
anyway. Right now I'm just throwing away lost data points entirely,
which loses the lost_{up,down} information. Will fix that and also
figure out the right way to indicate losses.

-Toke


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