Re: [Bloat] [Cerowrt-devel] FQ_Codel lwn draft article review

["Toke Høiland-Jørgensen" <toke@toke.dk>]

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Oliver Hohlfeld
<oliver@net.t-labs.tu-berlin.de> writes:

> The jitter measurements you have in mind will give you an idea on the
> jitter specific to the chosen traffic scenario, nothing more --- and
> in particular not the VoIP quality (although low vs. high jitter could
> /indicate/ certain /possible/ quality degradations).

Well no, in this sense the only "real" test for voip quality is picking
up the (soft)phone and talking to someone. However, since the context
here is automated measuring tools (preferably generating solid
quantitative, comparable data), that is hardly feasible.

I guess the goal of a comprehensive testing suite is to gather as many
indicators of quality degradations (in the widest possible sense) as
possible and testing for them under a variety of traffic conditions. I
am by no means an expert on VoIP, but someone suggested measuring jitter
could be useful, and I've proposed a possible way to do that (using
iperf udp flows at a low-ish bandwidth).

Since for the purpose of this particular discussion I seem to be in the
test tool building business (at least for the time being), what I really
need before going forward with this is someone to comment on (a) if
using iperf udp flows is a valid way to measure jitter, (b) if measuring
jitter is actually something someone wants to do and (c) if there are
other tests that would be useful for testing VoIP (or general)
conditions instead of / in addition to the jitter measurements.

So far I don't have an answer to (a), only negative answers to (b) and
nothing concrete for (c). So for the time being I'm shelving the idea,
and will just note that it seems quite feasible to return to it should
someone change their mind on (b) :)


-Toke

-- 
Toke Høiland-Jørgensen
toke@toke.dk

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