Re: [Bloat] Updated Bufferbloat Test

[Simon Barber <simon@superduper.net>]

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Yes, if you want to know how well real time communication is going to work, 
something close to peak or 95%ile of total latency is the relevant measure.

Showing less data and keeping it simple is ideal, so users don't get confused.

Simon

On February 25, 2021 12:11:02 PM Sina Khanifar <sina@waveform.com> wrote:

> Thanks for the kind words, Simon!
>
>> Since you are measuring buffer bloat - how much latency *can* be caused by 
>> the excessive buffering, expressing the jitter number in terms of 95%ile 
>> would be appropriate - as that’s closely related to how large the excessive 
>> buffer is. The average jitter is more related to how the competing TCP 
>> streams have some gaps due to congestion control and these gaps can 
>> temporarily lower the buffer occupancy and result in a lower average jitter 
>> number.
>
> I'm thinking that we might even remove jitter altogether from the UI,
> and instead just show 95%ile latency. 95%ile latency and 95%ile jitter
> should be equivalent, but 95% latency is really the more meaningful
> measure for real-time communications, it feels like?
>
> On Thu, Feb 25, 2021 at 11:57 AM Simon Barber <simon@superduper.net> wrote:
>>
>> Hi Sina,
>>
>> That sounds great, and I understand the desire to separate the fixed 
>> component of latency and the buffer bloat / variable part. Messaging that 
>> in a way that accurately conveys the end user impact and the impact due to 
>> unmitigated buffers while being easy to understand is tricky.
>>
>> Since you are measuring buffer bloat - how much latency *can* be caused by 
>> the excessive buffering, expressing the jitter number in terms of 95%ile 
>> would be appropriate - as that’s closely related to how large the excessive 
>> buffer is. The average jitter is more related to how the competing TCP 
>> streams have some gaps due to congestion control and these gaps can 
>> temporarily lower the buffer occupancy and result in a lower average jitter 
>> number.
>>
>> Really appreciate this work, and the interface and ‘latency first’ nature 
>> of this test. It’s a great contribution, and will hopefully help drive ISPs 
>> to reducing their bloat, helping everyone.
>>
>> Simon
>>
>>
>> > On Feb 25, 2021, at 11:47 AM, Sina Khanifar <sina@waveform.com> wrote:
>> >
>> >> So perhaps this can feed into the rating system, total latency < 50mS is 
>> an A, < 150mS is a B, 600mS is a C or something like that.
>> >
>> > The "grade" we give is purely a measure of bufferbloat. If you start
>> > with a latency of 500 ms on your connection, it wouldn't be fair for
>> > us to give you an F grade even if there is no increase in latency due
>> > to bufferbloat.
>> >
>> > This is why we added the "Real-World Impact" table below the grade -
>> > in many cases people may start with a connection that is already
>> > problematic for video conferencing, VoIP, and gaming.
>> >
>> > I think we're going to change the conditions on that table to have
>> > high 95%ile latency trigger the degraded performance shield warnings.
>> > In the future it might be neat for us to move to grades on the table
>> > as well.
>> >
>> >
>> > On Thu, Feb 25, 2021 at 5:53 AM Simon Barber <simon@superduper.net> wrote:
>> >>
>> >> So perhaps this can feed into the rating system, total latency < 50mS is 
>> an A, < 150mS is a B, 600mS is a C or something like that.
>> >>
>> >> Simon
>> >>
>> >> On February 25, 2021 5:49:26 AM Mikael Abrahamsson <swmike@swm.pp.se> wrote:
>> >>
>> >>> On Thu, 25 Feb 2021, Simon Barber wrote:
>> >>>
>> >>>> The ITU say voice should be <150mS, however in the real world people are
>> >>>> a lot more tolerant. A GSM -> GSM phone call is ~350mS, and very few
>> >>>> people complain about that. That said the quality of the conversation is
>> >>>> affected, and staying under 150mS is better for a fast free flowing
>> >>>> conversation. Most people won't have a problem at 600mS and will have a
>> >>>> problem at 1000mS. That is for a 2 party voice call. A large group
>> >>>> presentation over video can tolerate more, but may have issues with
>> >>>> talking over when switching from presenter to questioner for example.
>> >>>
>> >>>
>> >>> I worked at a phone company 10+ years ago. We had some equipment that
>> >>> internally was ATM based and each "hop" added 7ms. This in combination
>> >>> with IP based telephony at the end points that added 40ms one-way per
>> >>> end-point (PDV buffer) caused people to complain when RTT started creeping
>> >>> up to 300-400ms. This was for PSTN calls.
>> >>>
>> >>> Yes, people might have more tolerance with mobile phone calls because they
>> >>> have lower expectations when out and about, but my experience is that
>> >>> people will definitely notice 300-400ms RTT but they might not get upset
>> >>> enough to open a support ticket until 600ms or more.
>> >>>
>> >>> --
>> >>> Mikael Abrahamsson    email: swmike@swm.pp.se
>> >>
>> >>
>>


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