[ale] Cablemodem problems (Charter); DSL maybe

[Ken Cochran]

>Date: Tue, 21 Aug 2007 09:29:12 -0400
>From: "John C" <jcouncilman at knology.net>
>To: "Atlanta Linux Enthusiasts" <ale at ale.org>
>Subject: Re: [ale] Cablemodem problems (Charter); DSL maybe
>
>
>>From my experience working in a cable plant, this sort of problem is more
>than likely with the return signal.  Cable modems operate on a forward and
>reverse (transmit and receive) signal.  The forward signal can be fine
>(which is why your TV works), but the cable modem will still be down since
>it can't talk back to the CMTS (cable modem router).  The upstream path is
>usually on the lower frequencies and are affected a lot more by
>interference.

Indeed.  When the outage is in progress, traceroute doesn't
get *anywhere*; what I think is the CMTS is hop 1 & I don't
even get that far.

>The technician needs to attach a signal generator onto your cable outlet and
>DRIVE back to the nearest hub site.  From there he can measure the signal
>level of the return path.  If they did not do that, then they have no way to
>diagnose the problem.

Have done that before.  A few times...

>When the tech said that he had to rebalance the lines, he needs to do the
>same thing.  Inject at your house and check the signal at each amplifier and
>node along the way (adjusting it as needed).

What I don't understand is the need to do that every 3-4 months
(e.g. seasonally).  This is an almost regularly  recurring
(at least a couple of years now) problem.

>There is a way to get into the cable modem's diagnostic web page (built into
>all cable modems), but it's been a while since I used it and can't remember
>how to get in.

Yup, am there alot, unless there's some secret/hidden one.
It says signal strength & s:n ratios are good, both forward
& reverse.  When talking with their customer service, they
report good signals too, *even when my IP is down & not talking
with anything*.

>John

-kc

>On 8/21/07, James P. Kinney III <jkinney at localnetsolutions.com> wrote:
>>
>> Sounds like grounding is OK. The only other thing I can think of is to
>> check, clean and use no-corrode grease on the threads of the incoming
>> ferrule. That should _not_ be an issue as the metal on that stuff is
>> generally quite weather resilient.
>>
>> Another factor I have seen is a center conductor cut slightly too short.
>> As temperature and wind make the hanging wire move, expand and contract,
>> the connection would vary enough to act like a notch filter. The pole
>> end was where my issue was.
>>
>> On Mon, 2007-08-20 at 23:17 -0400, Ken Cochran wrote:
>> > >From: "James P. Kinney III" <jkinney at localnetsolutions.com>
>> > >Date: Mon, 20 Aug 2007 17:23:22 -0400
>> > >Subject: Re: [ale] Cablemodem problems (Charter); DSL maybe
>> > >
>> > >
>> > >For reasons best left to <rant> formatting, cable modems are apparently
>> > >very picky about grounding. To add to that, they are also very poorly
>> > >installed in most situations. The best thing _you_ can do is to get a
>> > >groundrod from the hardware store and pound it in yourself. Then run
>> > >appropriately sized bare copper from the ground in your power breaker
>> > >box to it. Repeat for the ground connection from the cable feed. Be sure
>> > >to use solid mechanical connection and use the anti corrosion grease.
>> >
>> > Both telco & cable enter the house by "their" NIDs, each on the
>> > outside wall nearby the electrical service/meter.  All are
>> > common-grounded (per code) to a single deep-driven rod directly
>> > below the power box (constructed in early 1970s).  It's on a
>> > lake, so there is a high water table; I'd think that would make
>> > for very good grounding.  (?)  Grounding has been inspected
>> > before, by both telco & cableco techs & by me & my electrician(s)
>> > and they report no problems.  And it looks good to me now.  {shrug}
>> >
>> > Services are underground in plastic conduit from the house to a
>> > pole, about 75 feet, and from that pole to the street pole, in
>> > the air about another 75-80 feet.  The "middle" pole is *not*
>> > grounded, neither for phone nor cable nor power; also, it's on
>> > "their" side of any NIDs, so any grounding there is utilities'
>> > responsibility.  I think the "street" pole is grounded for
>> > everything.  (Hmm, it'd have to be, it has a power transformer
>> > too and the power people here *always* ground transformers.)
>> >
>> > Internal house cabling is RG-6 with "snap'n seal" conectors.
>> > >From the house to the street is RG-11, with similar connectors.
>> >
>> > Any other ideas?  I just can't believe the cableco's outside
>> > plant is so temperature sensitive that they have to have a
>> > crew "retune" it seasonally.  But right now I'm not getting
>> > more than about 30 minutes at a time of ip-connectivity.
>> > Then it's out for roughly another 30 minutes, "cycling" like
>> > this all the time.
>> >
>> > -kc
>> >
>> > >On Mon, 2007-08-20 at 16:21 -0400, Ken Cochran wrote:
>> > >> Hi ALErs:
>> > >>
>> > >> Sort of a 2-part question/problem, cablemodem problems vs DSL:
>> > >> (Lesser of 2 evils?)
>> > >>
>> > >> 1.  (Charter) Cablemodem service problems:  You folks in the
>> > >>     cableco/outside plant world can maybe help me with this?
>> > >>
>> > >> I've been having problems with Charter (cablemodem) for a long
>> > >> time now (a couple of years or more, I track the tickets) and I'm
>> > >> wondering if now that I can get dsl at my location, it might be
>> > >> time to change.
>> > >>
>> > >> At roughly regular intervals of every few months, I get sporadic
>> > >> loss & restart of IP, TV works fine, usually the cablemodem
>> > >> itself (& subsequently the dispatched tech) reports good signal
>> > >> levels/s:n ratios, etc.  What happens is a loss of Internet
>> > >> communications every few minutes, lasting for a few minutes.
>> > >> Netstat reports non-zero send-Qs when this is "underway."
>> > >> Traceroute doesn't even make it as far as the 1st hop.  A little
>> > >> while later, things resume as if nothing ever happened.  This
>> > >> repeats all the time.  Currently, this has been happening since
>> > >> Friday afternoon and has not been corrected.  Last time (mid-May
>> > >> 2007) also took several days to correct.  The cablemodem itself
>> > >> reported a borderline signal level; repair took a line tech.
>> > >>
>> > >> Last couple of times (& now, still experiencing this), the
>> > >> visiting (house services) tech says he has to dispatch a "line
>> > >> tech" to "rebalance" (?) the neighborhood lines (along the
>> > >> street).  He says it is because of the change in (weather)
>> > >> seasons and/or ambient temperatures (going either hot or cold)
>> > >> that causes this & line techs have to come out & rebalance these
>> > >> a few times per year (roughly seasonally).  Any idea(s) as to
>> > >> just what is happening here?  Sounds like BS to me; I find it
>> > >> hard to believe that a cableco has to go out & redo its outside
>> > >> plant 2-4 times a year to correct for what sounds to me like
>> > >> design deficiencies in said outside plant.
>> > >>
>> > >> Some local setup details:
>> > >> Cablemodem is a Motorola SurfBoard SB4101.  Distance from service
>> > >> entrance to the "node" (coax to fiber converter) is about 2000
>> > >> feet via coax that's about as big around as my thumb.  Outside
>> > >> plant is from Scientific Atlanta.