[ale] Cablemodem problems (Charter); DSL maybe

Tue Aug 21 09:29:12 EDT 2007

>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.

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.

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).

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.

John

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.
> > >>
> > >> 2.  DSL:  Location, Alexander City, Alabama (east central AL),
> > >>     ILEC & my local service is Bellsouth/ATT and DSL has only
> > >>     recently become available at my location.  It looks like my
> > >>     pickins' are slim wrt carriers.  I'm about 6500 feet from the
> > >>     "remote" box (or pair-gain mux or whatever they're calling
> > >>     that thing nowadays...) that serves my area.
> > >>
> > >> a.  Recommended (or not) carriers
> > >>     Unless some things have changed/added, I think Bellsouth/ATT
> > >>     might be my only option for DSL but I need to check further.
> > >>     Any recommendations for/against alternatives?  I think my
> > >>     available options *might* be HiWaay (hq in Huntsville AL) or
> > >>     maybe SpeakEasy (but last time I checked, they don't serve
> > >>     here) or EarthLink/Mindspring (also an unknown right now).
> > >>     Looks like I *can* get the $10/month DSL here (with the 1yr
> > >>     committment of course); anyone besides Bellsouth/ATT doing
> > >>     anything similar?  Naturally I have problem(s) with ATT's
> > >>     customer monitoring but I may have to put up with this
> > >>     nastiness just to have Internet access that works at all. :-(
> > >>
> > >> b.  NAT issues
> > >>     I see the little Westell modems from Bellsouth at customers'
> > >>     homes & notice the following:
> > >>     -  The modem itself handles the PPPoE/PPPoA stuff nowadays,
> > >>        so no need for that on the client computer.
> > >>     -  The client computer gets a gets an RFC1918 private
> > >>        address, 192.168.100.x iirc.
> > >>
> > >>     My own internal private network is also RFC1918 & 192.168.x.y.
> > >>     If I change to DSL with its required PPPo{EA}, it appears
> > >>     that I'll become "double-NAT"ed; is this a problem?  If so,
> > >>     how do I deal with it?
> > _______________________________________________
> > Ale mailing list
> > Ale at ale.org
> > http://www.ale.org/mailman/listinfo/ale
> >
> --
> James P. Kinney III
> CEO & Director of Engineering
> Local Net Solutions,LLC
> 770-493-8244
> http://www.localnetsolutions.com
>
> GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
> <jkinney at localnetsolutions.com>
> Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
>
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://www.ale.org/mailman/listinfo/ale
>
>
-------------- next part --------------
An HTML attachment was scrubbed...