From: Greg White <g.white@CableLabs.com>
To: Simon Barber <simon@superduper.net>
Cc: "Toke Høiland-Jørgensen" <toke@toke.dk>,
"bloat@lists.bufferbloat.net" <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] [Cerowrt-devel] FQ_Codel lwn draft article review
Date: Wed, 28 Nov 2012 14:40:11 -0700 [thread overview]
Message-ID: <CCDBD0C9.16BF5%g.white@cablelabs.com> (raw)
In-Reply-To: <50B669E5.8020105@superduper.net>
Good point. I wrote that without double checking my code. What I
should've said was:
Latency is min_latency + 60ms.
This is under the assumption of a fixed 60ms dejitter buffer that is
prescient as to what the min_latency will be.
-Greg
On 11/28/12 12:45 PM, "Simon Barber" <simon@superduper.net> wrote:
>Not sure why you would use mean latency - for VoIP the thing that
>matters is maximum latency - if some packets are late, then you don't
>hear them. More precisely a small packet loss rate is OK, so you should
>use something like the 99th percentile of latency. In my last jitter
>buffer implementation I ran an estimator for 99th percentile latency,
>and added 5ms.
>
>That said, most jitter buffers in use are poor implementations, and
>introduce more latency than necessary.
>
>Simon
>
>
>On 11/28/2012 11:21 AM, Greg White wrote:
>> Jitter on its own is not useful for estimating VoIP quality.
>>
>> For (c), I've used:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Cole, Robert G., and Joshua H. Rosenbluth. "Voice over IP
>>performance
>> monitoring." ACM SIGCOMM Computer Communication Review 31, no. 2 (2001):
>> 9-24.
>>
>> Which I generally simplify to:
>>
>>
>>
>>
>>
>>
>>
>>
>> R= 94.2 - 0.024*Latency - 0.11*max(0,Latency-177.3 ms) - 30*log(1 +
>> 15*Loss).
>>
>>
>>
>>
>>
>> where Loss is mean packet loss rate (counting packets with latency >
>> (min_latency + 60ms) as lost), Latency is mean latency for packets not
>> counted as lost.
>>
>>
>>
>>
>>
>>
>> You can then translate R into an estimate of MOS using Eq.1 in the above
>> reference.
>>
>> -Greg
>>
>>
>> On 11/27/12 5:51 PM, "Toke Høiland-Jørgensen" <toke@toke.dk> wrote:
>>
>>> 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
>>
>> _______________________________________________
>> Bloat mailing list
>> Bloat@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/bloat
>>
next prev parent reply other threads:[~2012-11-28 21:39 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAA93jw5yFvrOyXu2s2DY3oK_0v3OaNfnL+1zTteJodfxtAAzcQ@mail.gmail.com>
2012-11-23 8:57 ` [Bloat] " Dave Taht
2012-11-23 22:18 ` Paul E. McKenney
2012-11-24 0:07 ` Toke Høiland-Jørgensen
2012-11-24 16:19 ` Dave Taht
2012-11-24 16:36 ` [Bloat] [Cerowrt-devel] " dpreed
2012-11-24 19:57 ` [Bloat] [Codel] " Andrew McGregor
2012-11-26 21:13 ` Rick Jones
2012-11-26 21:19 ` Dave Taht
2012-11-26 22:16 ` [Bloat] " Toke Høiland-Jørgensen
2012-11-26 23:21 ` Toke Høiland-Jørgensen
2012-11-26 23:39 ` [Bloat] [Cerowrt-devel] " dpreed
2012-11-26 23:58 ` Toke Høiland-Jørgensen
2012-11-27 16:41 ` Oliver Hohlfeld
2012-11-28 0:51 ` Toke Høiland-Jørgensen
2012-11-28 19:21 ` Greg White
2012-11-28 19:45 ` Simon Barber
2012-11-28 20:01 ` Oliver Hohlfeld
2012-11-28 21:40 ` Greg White [this message]
2012-11-28 20:09 ` Oliver Hohlfeld
2012-11-28 21:45 ` Greg White
2012-11-26 17:20 ` [Bloat] " Paul E. McKenney
2012-11-26 21:05 ` [Bloat] [Codel] " Rick Jones
2012-11-26 23:18 ` Rick Jones
2012-11-27 22:03 ` [Bloat] [Cerowrt-devel] " Jim Gettys
2012-11-27 22:31 ` David Lang
2012-11-27 22:54 ` Paul E. McKenney
2012-11-27 23:15 ` [Bloat] [Codel] " Andrew McGregor
2012-11-28 0:51 ` Paul E. McKenney
2012-11-28 17:36 ` Paul E. McKenney
2012-11-28 14:06 ` [Bloat] " Michael Richardson
2012-11-27 22:49 ` Paul E. McKenney
2012-11-27 23:53 ` [Bloat] [Codel] " Greg White
2012-11-28 0:27 ` Paul E. McKenney
2012-11-28 3:43 ` Kathleen Nichols
2012-11-28 4:38 ` Paul E. McKenney
2012-11-28 16:01 ` Paul E. McKenney
2012-11-28 16:16 ` Jonathan Morton
2012-11-28 17:44 ` Paul E. McKenney
2012-11-28 18:37 ` Michael Richardson
2012-11-28 18:51 ` Eric Dumazet
2012-11-28 21:44 ` Michael Richardson
2012-11-28 19:00 ` Eric Dumazet
[not found] ` <87vcckb0el.fsf@toke.dk>
2012-12-02 21:47 ` Andrew McGregor
2012-12-03 8:04 ` Dave Taht
2012-12-02 22:07 ` Eric Dumazet
[not found] ` <87lidgaynn.fsf@toke.dk>
2012-12-02 22:30 ` Eric Dumazet
2012-11-28 17:20 ` [Bloat] " Paul E. McKenney
[not found] ` <20121202230635.GA16359@linux.vnet.ibm.com>
[not found] ` <87obib5qf8.fsf@toke.dk>
2012-12-03 11:31 ` Dave Taht
[not found] ` <87fw3n5m9g.fsf@toke.dk>
2012-12-03 14:58 ` Paul E. McKenney
2012-12-03 15:49 ` [Bloat] [Codel] " Eric Dumazet
2012-12-03 15:03 ` [Bloat] " Paul E. McKenney
2012-12-03 15:58 ` David Woodhouse
2012-12-04 3:13 ` [Bloat] [Codel] " Dan Siemon
2012-12-04 9:23 ` Alex Burr
2012-12-05 3:41 ` Dan Siemon
2012-12-05 20:33 ` Alex Burr
2012-12-06 4:12 ` Dan Siemon
2012-12-06 23:41 ` Alex Burr
2012-12-05 0:01 ` Sebastian Moeller
2012-11-30 1:09 ` [Bloat] " Dan Siemon
2013-01-01 20:50 ` Dan Siemon
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