[Bloat] unfixable bloat on Cable modem CODA-4680 (puma 7)

cloneman bufferbloat at flamingpc.com
Thu Mar 28 16:44:52 EDT 2019

I have discovered the source of the confusion. This is different, but
similar to  PUMA6 problems, I think.
Certain types of traffic are getting de-prioritized, especially small
packets under load.


Normal ping:
 Minimum = 17ms, Maximum = 734ms, *Average = 202ms*

Large 1472-byte ping
 Minimum = 18ms, Maximum = 229ms, *Average = 47ms*

TCP-Based ping via psping.exe
 Minimum = 14.15ms, Maximum = 40.39ms, *Average = 25.88ms*

For more fun:

ICMP in a VPN, ping set to 13-bytes
Minimum = 36ms, Maximum = 602ms, *Average = 208ms*

ICMP in a VPN, 1300 bytes
 Minimum = 24ms, Maximum = 72ms, *Average = 40ms*

This explains why certain synthetic bufferbloat benchmarks were passing
with flying colors but my basic ICMP ping was terrible under load. VPN does
not seem to help, so it's not packet inspection... it's failure of tiny
packets and success of larger, normal ones.

The problem only occurs during download stress, not upload stress. Anyway,
I guess this is mostly an FYI.
Perhaps  a script that  does variable packet sizes for the generated small
flow traffic could be useful to someone in the future.

On Thu, Mar 28, 2019 at 8:03 AM Sebastian Moeller <moeller0 at gmx.de> wrote:

> HI cloneman,
> maybe have a look at http://www.dslreports.com/tools/puma6?
> > On Mar 28, 2019, at 12:00, cloneman <bufferbloat at flamingpc.com> wrote:
> >
> > I'm getting a weird problem with this new modem , it's Docsis 3.1
> >
> > latency/jitter measured via ping is about ~300ms during download
> pressure of 3 http transfers. The latency doesn't appear on synthetic
> bufferbloat benchmarks, though. (dslreports ; 20ms ("A")
> >
> > question: trying to figure out why I'm seeing this particular behavior,
> and determine if it'd a real issue or just an anomalie with ICMP traffic
> >
> > I've not seen ping do this with other modems.
> >
> > Perhaps I need to try some other traffic generation/ capture  tools?
> >
> >
> > _______________________________________________
> > Bloat mailing list
> > Bloat at lists.bufferbloat.net
> > https://lists.bufferbloat.net/listinfo/bloat
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