[conspire] Comcast jamboree, day deux

[Michael Paoli]

> From: "Rick Moen" <rick at linuxmafia.com>
> Subject: [conspire] Comcast jamboree, day deux
> Date: Fri, 26 Feb 2021 01:48:02 -0800

> For years, we've noticed sometimes the Cisco DPC3941B DOCSIS 3.0 24x4
> Wireless Business Gateway box goes through multiple reboots during the
> middle of the night, which we alway guesstimated to mean a remotely
> triggered maintenance regime right out of 'The Office' ('Have you tried
> turning it off and back on again?').  Like, maybe Comcast Corporate was
> aware of these SOHO gateways being a foetid pile of dingo's kidneys
> prone to RAM exhaustion and becoming unable to maintain their state
> tables, and so just had a cron job to force-reboot them frequently.

For better and/or worse ... Comcast Business ... if one logs into
one's account on their (support) site, from there (e.g. alternative
connectivity such as "smart" phone), can do some basic health checks
and even reboot the router device.  Also kind'a handy if one suspects
a problem - to see if Comcast can "see" the router device from their
side of things.  Oh, and I happen to have same model - Comcast
mostly puts their own labeling on it, but the device identifies itself
easily enough:
Model:DPC3941B
Vendor:Cisco
Hmmm, I don't seem to get the long frequent reboots ... occasional
shorter outages - when I presume they're doin' firmware updates or
whatever - so there are those disruptions - definitely not the rock
solid reliability of Raw Bandwidth connectivity - but thus far seems
mostly not too bad/horrible - at least in my limited experience (your
mileage may vary).

> just before midnight, and, suspiciously right _at_ midnight, we suddenly
> had no bandwidth across our uplink.  I observed to Deirdre that, during

> After a couple of basic checks, he yanked the Cisco DPC3941B out with my
> blessing -- and brought in from his van a Technicolor model CGA4131COM
> replacement gateway, did basic configuration, and then politely invited

> So far:  The new gateway box performs rather a lot better than the old
> one, but I'll skip details for length's sake.

Sounds good - maybe the older one was a lemon, or turned flakey ...
or maybe your line conditions aren't quite as good and it can't handle
that as well as some other models?  Who knows, ... though sounds most
likely it was just goin' flakey and into hard failin' territory.

> However:  Cheryl is paying $18.45 per month ($221.40/year) to _rent_ the
> damned gateway box (an underpowered and overfeatured thing where Comcast
> has root remotely), which seems frankly stupid.  I gather that the

Comcast Business doesn't specify exactly what's required by protocol(s)
and such.  Rather they specify you can (if not doing phone through
Comcast), use your own device and not pay the rental.  However, they
specify the allowable devices not by protocol, but by make and model -
I think they specify 3 or 4 possibilities.  I'm guestimating they do it
that way for support reasons - so they can have their low-end tech folks
walk the flowchart questions, and not have too many branches to follow
to do stuff like get model from customer, make certain checks regarding
'da blinkin' lights, etc.  And, as for cost / ROI, etc., last I checked,
between used/refurbished, up through about brand spanking sealed new with
warranty, the things seemed to range from roughly $20.00 to $130.00 USD or
so - in all case ROI of well under a year ... heck, one could buy two for
redundancy, and still have ROI of well under 2 years - even brand new ones
under warranty.  If one does the phone with Comcast, though, they they won't
let you use your own device.  And the rental and the device - can stop that
at any time - just return it to 'em and put an end to that cost (don't know
that they prorate it to the day, but ought at least cut that cost from
future months / billing cycles).

> 'modem' (terminal adapter) portion must comply with the DOCSIS 3.0 (or
> 3.1?) (Data Over Cable Service Interface Specification) spec, but
> otherwise could be anyone's hardware (and I'm not interested in

Might be feasible to reverse-engineer the requirements, by checking specs
of the models they support/allow.  And then "unsupported" device would
probably work fine ... don't know if DOCSIS protocol or the like would even
let 'em figure out remotely what the device itself actually was.

> Something like a Motorola MB7621 ($78 online) would suffice.  That's
> _just_ a 'modem', not providing a firewall, a DHCPd, or a WAP.  Nor does
> it have eight ethernet ports like the Technicolor model CGA4131COM, but
> rather one ethernet port -- because, frankly, that's what you have an
> ethernet switch for.  And we already have a bunch of WAPs, separately.

Yep, I too have Ethernet switch - so really don't need extra ports,
(or Wi-Fi, etc.) on the "router" device.  I in fact disabled the Wi-Fi
(through the management interface) - egad, there are some "home router"
type devices that don't even let one disable the Wi-Fi ... ugh.  I think
I saw that on some AT&T 2Wire device(s) ... closest I could find to disabling
Wi-Fi on that (was friend/family setup, not mine), could set the Wi-Fi
transmission power to absolute minimum, and set a good strong (random
cryptic) password.  But alas, couldn't actually turn it off or disable it.

> They connect to ethernet switches just fine.  ($221.40/year in rent,
> wow.  Sucker bait.)

Yeah, on my todo list (and has been quite a while ... not top-of-the
list, but hey, at least it's on the list).

> In the category of actual progress, with Duncan's good offices, we got
> all new ethernet cabling strung across the subflooring and passed up
> into the living room adjoining the Technicolor model CGA4131COM -- such
> that, perhaps tomorrow, I can finally re-unify the shambles that was
> left when Raw Bandwidth cut off ADSLv1 service and left about half the
> computing devices in my house with no uplink.

Ah, nice to have good cabling.  :-)