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

Pete Heist notifications at github.com
Thu Nov 16 14:36:30 EET 2017

> On Nov 16, 2017, at 1:15 PM, Toke Høiland-Jørgensen <notifications at github.com> wrote:
> Meh, irtt's functionality is basically a superset of netperf's UDP_RR.
> So automatically picking irtt if available and a fallback is the right
> thing to do, I think. I'd just add the plots everywhere, and if OWD data
> is not available, those plots would just be empty. Same thing we do for
> TCP window stats currently. Longer term, maybe hiding the plots entirely
> when there is no data is better, but for now empty plots are fine.

I see, that does keep it simpler.

> > Personally I don't think it's necessary to check for server-side
> > support. If someone is specifying they want to use a particular tool,
> > I think they're declaring that it's available, as it is today with
> > netperf / netserver.
> Yes, but if we do automatic detection with a preference we could get
> into the situation where irtt exists on the client but the test is being
> run against a server that doesn't have it. This is especially likely to
> happen before the *.netperf.bufferbloat.net servers have irtt deployed.
> Could you be persuaded to add a 'check_server' action to irtt? Something
> that just does the handshake and doesn't run any more tests other than
> that. Then we could have Flent call that to verify that irtt is
> usable...

Sure, I’ll add that (or something similarly named). Should get to it today or tomorrow. Meanwhile you’re right that something like this works and check for return code 0 to mean success:

irtt client -i 1ms -d 1ms -wait 1ms a.b.c.d

The handshake takes up to 15 seconds to complete (delays of 1, 2, 4 and 8 seconds waiting for a reply), so not having irtt on the server will mean a 15 second wait. Do you think it’s ok to keep that fixed?

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