
Some chip makers have hidden latency and jitter issues from common tests - based2
http://www.badmodems.com/
======
jimrandomh
tl;dr: The Intel Puma 6 and Puma 7 chipsets have a performance issue in a part
of the packet processing that is specific to TCP/IP, which went undetected for
awhile because "ping" packets are not TCP/IP. Modems that use the affected
chipset will have high jitter under load (especially load consisting of many
short connections), and will suffer denial of service when sent traffic with
many different port numbers. Additionally, under a previous firmware (but
according to a commenter on
[https://www.reddit.com/r/news/comments/7fjvvt/hundreds_of_mi...](https://www.reddit.com/r/news/comments/7fjvvt/hundreds_of_millions_of_cable_modems_affected_by/)
not on the most recent firmware), a timed process would briefly block
throughput every 2 seconds, adding to jitter issues. DSLReports has created a
tool which checks for this at
[http://www.dslreports.com/tools/puma6](http://www.dslreports.com/tools/puma6)
.

~~~
userbinator
Does anyone here know why these modems even care about TCP/IP or ICMP or any
other protocol higher than the network and physical layers? I could go read
the DOCSIS spec in detail, but thought these operated at a similar layer to
Ethernet (OSI layers 1 and 2.)

~~~
rasz
They dont, This TLDR is wrong.

Puma 5 shipped with just enough resources for 8 downstream channels. Puma 6
has same resources, but 16 downstream channels. Bottleneck is in hardware
accelerating packet decoding/assembly, queue/buffer is too shallow and more
packets in flight result in stalls. You can disable this hardware block and
magically modem stops being susceptible to DOS, but max throughput goes down
to ~60Mbit (opposed to theoretical ~800Mbit with ~2Mbit DOS potential)

There are people with Puma 6 with ISP using only 6 downstream channels and
their modems work just great. 8 is barely acceptable (even puma 5 has problems
on the test and can be DOSed by ~10Mbit), 16 is just plan broken.

~~~
nalllar
DOCSIS "modems" are layer 3 devices as well actually.

The DOCSIS standard requires filtering by IP address and port [1] built in to
the modem, instead of at the CMTS. This is back-asswards, as a hacked modem
can ignore the filtering, but it's part of the spec.

There are multiple sources of jitter in the puma 6/5: more channels = more
jitter, more flows = more jitter/complete failure at ~2000 separate active
flows in a 1 second period.

[1]: [http://www.cable-europe.eu/wp-content/uploads/bsk-pdf-
manage...](http://www.cable-europe.eu/wp-content/uploads/bsk-pdf-manager/2_CM-
SP-OSSIV3.0-I15-110623.PDF) \- Annex F Protocol Filtering (Normative)

------
userbinator
Judging by the picture on the main page, I thought it would be about them
overheating and catching fire...

 _Until Intel released its Puma 6 chip Broadcom dominated the modem chip
market. The Broadcom chip does not have latency or jitter issues._

As much as I hate them, Broadcom dominates the market because (as long as you
don't ask for source code or Linux or datasheets...) their modems and other
networking devices generally work. I'm guessing the cause of this jitter is
because Intel is trying to do more in software vs. the dedicated hardware
Broadcom uses.

The DoS on the "Security Issues" page is even more unusual, unless these
modems are actually more than just modems and include a router/NAT too?

~~~
revelation
In what world do WLAN & Bluetooth generally just work? Those are pretty much
the remaining bastions of horrible software support, and for no good reason
whatsoever.

Even the graphics vendors have got their shit together. That's how hopeless
Broadcom is.

~~~
bsamuels
bluetooth will generally "just work" when using two devices with the same
manufacturer's chipset (this is not a rule by any measure though).

in my experience, many bluetooth hiccups are caused by manufacturers having
alternate readings of the bluetooth spec, which is a massive, hard to swallow
behemoth.

if you have two 1st party BTLE devices, you can expect to see bluetooth at its
best. for example, apple airpods + iphone are probably as good as youll ever
see a bluetooth pairing.

~~~
madeofpalk
To be fair, AirPods + iPhone are using more than standard Bluetooth - Apple
has their _magic sauce_ on top to make things work super smoothly especially
for the initial pairing.

~~~
ztjio
You can still use AirPods with non-Apple Bluetooth devices. The pairing
process isn't as braindead easy of course, but they do work. That implies they
adhere to the standard at least to some degree.

I personally only use my AirPods with Apple products so I can't speak to
whether they perform less well on regular devices, but, I somehow doubt it.
Beyond pairing, it seems the only remaining secret sauce is in the relay
between the two earbuds and coordination between the to for which one actually
connects to the source device. None of that matters for the BT spec.

------
existencebox
This is a bit of a rant, and a bit of an open question of "is there really
nothing more I can do."

I'm more than a little furious that after being sold a product that explicitly
fails under load, the best we have in terms of consumer protections is a class
action that, if my history of class actions holds true, will accomplish little
to nothing to either punish intel or compensate the consumers.

For the last year I've been putting up with network issues that I thought were
a result of the house I moved into, when now I find out that the sb6190 I
spent a silly amount of money on has been degrading an equally not-cheap
internet plan for the entire time. And now my best approach is "deal with it,
spend 200$ more."

Here's hoping consumers in the EU are more protected, for us in the US I don't
have my fingers crossed.

~~~
ztjio
The SB6190 is a $95 product right now. Plus, it's just DOCSIS 3.0. You can get
decent DOCSIS 3.0 modems for ~$50 if you don't need maximum speeds. If you've
got under ~300mbps connection, you could replace it pretty cheaply. For
example, a Motorola MB7220 is about $50 without any discounts. Even a 16x4 is
about $70. These are Broadcom based modems.

~~~
existencebox
A note, not to distract from the validity of your points, but the sb6190 used
to be 150 [0] (yes both prices are somewhat negligable in the long term but if
I phrase it in terms of "I'm out a nice dinner" vs 2 I'm still pretty miffed)

That being said, thanks for the clarity on 3.0 vs 3.1, I had pulled up the
recommended SB8200 since I had broadly heard positive things about Arris in
the past and saw it to be ~190; didn't realize the cutoff was as high as
300mbps, so I should be fine with my 250mb down to get a cheaper one.

[0][https://camelcamelcamel.com/ARRIS-SURFboard-SB6190-DOCSIS-
Ca...](https://camelcamelcamel.com/ARRIS-SURFboard-SB6190-DOCSIS-
Cable/product/B016PE1X5K?context=search)

~~~
ztjio
Yeah and with the 16-4's you can get like 686 or something. DOCSIS 3.0 is
pretty great still.

------
floatboth
Apparently this is about DOCSIS modems.

~~~
zentiggr
Can't help it...

"Apparently, it runs on some form of electricity."

------
based2
[https://www.reddit.com/r/news/comments/7fjvvt/hundreds_of_mi...](https://www.reddit.com/r/news/comments/7fjvvt/hundreds_of_millions_of_cable_modems_affected_by/)

------
dogruck
I’ll admit that I was initially confused by the link going to a picture of a
burning modem, instead of an article. Stupid me. Just follow the navigation
links on the left.

~~~
Animats
Yes. Site is awful. Result there are important. The site is so bad that it
makes the results look less credible.

~~~
cesarb
To me, it looks like a typical website design of the 90s: a left navigation
frame, with the contents in the right frame. In fact, according to the <meta>
tags, that site was made with FrontPage, as was common on that era.

~~~
Animats
It's not the technology, it's the awful graphics.

------
Pengwin
Not surprised to see a modem/router from Australia's biggest Telco on the
list.

Australia's internet is in such a confusing state. At the moment a house could
potentially get internet via one of ADSL1/2/2+, VDSL2+, HFC, Fiber, Wireless
or satellite and on top of that most telcos are shipping woefully bad
modems/router hardware with equally bad, gimped, and undersupported firmware
to consumers.

~~~
digi_owl
Sounds like Norway basically. Thankfully the local powerco decided to roll out
fiber in my area recently, and i think some 99% of the households jumped
onboard.

Before then it was all about ADSL2+ (or some such) over a aging copper pair.

------
colanderman
That site does also have a forum topic discussing alternatives to the SB6190:
[http://badmodems.com/Forum/viewtopic.php?f=9&t=5](http://badmodems.com/Forum/viewtopic.php?f=9&t=5)

------
solotronics
would this show up under an IPERF3 test? I would think so but just curious if
someone with one of these modems can check. Also curious if this shows up
testing between switch ports on the modem or if it's just IP outside the NAT.

~~~
floatingatoll
The dslreports forums have been studying this for a year or so, and should
have those details available.

From a practical perspective, if your modem is on the list, your apps and
browsers will load pages slowly, with weird delays all over the place (due to
DNS being Most Impacted by the Puma problems). Replace ASAP.

------
maxyme
If anyone doesn't know, always avoid Motorola/Arris Modems. I remember a few
years ago Arris tried to update my modem to add ipv6 support. Ended up having
2 months of constant issues where incoming connections to ports forwarded
would cause the router to drop all outgoing packets until the incoming
connection closed... 2 months later Comcast rolled back the update.

~~~
bri3d
Motorola/Arris modems can have 3 major chipsets (TI, Broadcom, Intel), each
with a multitude of firmware and configuration updates delivered on a per-
carrier basis, so this is a _very_ sweeping generalization. I'd recommend
researching a modem much more in depth than just the manufacturer name on the
front.

~~~
digi_owl
And this is a basic problem of the consumer networking market.

I know at least one box i have here are listed by 3 different variants on the
OEM site, and the only distinguishing factor is a single letter on a single
model code pinted on the sticker underneath it.

Checking the box or anything similar and you would be non the wiser.

