Perhaps where the green is should depend on the customer's access type. For
instance someone on fiber should have a much better ping than someone on
3G. But I agree this should be a fixed scale, not dependent on idle ping
time. Although VoIP might be good up to 100ms, gamers would want lower values.
Simon
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On April 24, 2015 1:19:08 AM Sebastian Moeller <[email protected]> wrote:
Hi jb,
this looks great!
On Apr 23, 2015, at 12:08 , jb <[email protected]> wrote:
> This is how I've changed the graph of latency under load per input from
you guys.
>
> Taken away log axis.
>
> Put in two bands. Yellow starts at double the idle latency, and goes to
4x the idle latency
> red starts there, and goes to the top. No red shows if no bars reach into it.
> And no yellow band shows if no bars get into that zone.
>
> Is it more descriptive?
Mmmh, so the delay we see consists out of the delay caused by the distance
to the server and the delay of the access technology, meaning the un-loaded
latency can range from a few milliseconds to several 100s of milliseconds
(for the poor sods behind a satellite link…). Any further latency
developing under load should be independent of distance and access
technology as those are already factored in the bade latency. In both the
extreme cases multiples of the base-latency do not seem to be relevant
measures of bloat, so I would like to argue that the yellow and the red
zones should be based on fixed increments and not as a ratio of the
base-latency. This is relevant as people on a slow/high-access-latency link
have a much smaller tolerance for additional latency than people on a fast
link if certain latency guarantees need to be met, and thresholds as a
function of base-latency do not reflect this.
Now ideally the colors should not be based on the base-latency at all but
should be at fixed total values, like 200 to 300 ms for voip (according to
ITU-T G.114 for voip one-way delay <= 150 ms is recommended) in yellow, and
say 400 to 600 ms in orange, 400ms is upper bound for good voip and 600ms
for decent voip (according to ITU-T G.114,users are very satisfied up to
200 ms one way delay and satisfied up to roughly 300ms) so anything above
600 in deep red?
I know this is not perfect and the numbers will probably require severe
"bike-shedding” (and I am not sure that ITU-T G.114 really iOS good source
for the thresholds), but to get a discussion started here are the numbers
again:
0 to 100 ms no color
101 to 200 ms green
201 to 400 ms yellow
401 to 600 ms orange
601 to 1000 ms red
1001 to infinity purple (or better marina red?)
Best Regards
Sebastian
>
> (sorry to the list moderator, gmail keeps sending under the wrong email
and I get a moderator message)
>
> On Thu, Apr 23, 2015 at 8:05 PM, jb <[email protected]> wrote:
> This is how I've changed the graph of latency under load per input from
you guys.
>
> Taken away log axis.
>
> Put in two bands. Yellow starts at double the idle latency, and goes to
4x the idle latency
> red starts there, and goes to the top. No red shows if no bars reach into it.
> And no yellow band shows if no bars get into that zone.
>
> Is it more descriptive?
>
>
> On Thu, Apr 23, 2015 at 4:48 PM, Eric Dumazet <[email protected]> wrote:
> Wait, this is a 15 years old experiment using Reno and a single test
> bed, using ns simulator.
>
> Naive TCP pacing implementations were tried, and probably failed.
>
> Pacing individual packet is quite bad, this is the first lesson one
> learns when implementing TCP pacing, especially if you try to drive a
> 40Gbps NIC.
>
> https://lwn.net/Articles/564978/
>
> Also note we use usec based rtt samples, and nanosec high resolution
> timers in fq. I suspect the ns simulator experiment had sync issues
> because of using low resolution timers or simulation artifact, without
> any jitter source.
>
> Billions of flows are now 'paced', but keep in mind most packets are not
> paced. We do not pace in slow start, and we do not pace when tcp is ACK
> clocked.
>
> Only when someones sets SO_MAX_PACING_RATE below the TCP rate, we can
> eventually have all packets being paced, using TSO 'clusters' for TCP.
>
>
>
> On Thu, 2015-04-23 at 07:27 +0200, MUSCARIELLO Luca IMT/OLN wrote:
> > one reference with pdf publicly available. On the website there are
> > various papers
> > on this topic. Others might me more relevant but I did not check all of
> > them.
>
> > Understanding the Performance of TCP Pacing,
> > Amit Aggarwal, Stefan Savage, and Tom Anderson,
> > IEEE INFOCOM 2000 Tel-Aviv, Israel, March 2000, pages 1157-1165.
> >
> > http://www.cs.ucsd.edu/~savage/papers/Infocom2000pacing.pdf
>
>
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