[Bloat] What does cablelabs certification actually do?

jb justin at dslr.net
Thu Dec 8 21:34:28 EST 2016


So a number of our users have ganged together to share information and
discovered that Puma6 chipset based cable modems all seem to have a very
bad flaw. Whether this flaw is fixable in firmware isn't known. The only
company initially participating in the discussion - Arris - has gone a bit

We built a tiny tool to identify whether a cable modem has the issue:

The distribution of latencies for a puma6 modem is terrible, stretching over
100ms and beyond often as high as 500ms. This appears to be some
kind of systemic packet loss or delay involving small packets and while it
doesn't influence speed over an established connection it screws up DNS
lookups and short TCP transactions. So its rather a strange issue but very
irritating for any owner of these new modems until it gets fixed.

The modem / chipset is increasingly widely used so we got the register to
warn about the issue, I think they are going to do a new article next week:

Anyway while looking at this data and the number of these Puma6 driven
modems out there now, I wondered how it got certified!

And then wondered why certification can't also include verification for
correctly sized buffers as well?
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