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December 8, 2005

Cable Fun

I’ve been a Time-Warner Roadrunner cable modem subscriber for many years now and, generally, the service has been decent, if somewhat expensive. Recently, though, it’s gone seriously downhill.

I generally have a couple of terminal sessions open with golem. With alarming frequency, nowadays, when I click on the terminal window and start typing, nothing echoes back. Sure enough, I click over to my web browser and try opening a new web page; the internet is unreachable. After a couple of minutes of pounding my fist and cursing at the computer, the network comes back. Web pages open again, the terminal sessions start echoing characters again and life returns to normal. For a while. Later in the evening, the same thing will happen again … and again.

Some have suggested that I call the Service department, and have them swap out my “bad” cable modem for a new one. But I don’t quite see why a modem that functioned just fine for years should suddenly turn “bad.” It’s not as if it’s broken down; 95% of the time, the connection is working fine.

On a hunch, I decided to do a little experiment and run a process which pings golem at regular intervals (one 64 byte ICMP packet every 10 seconds). And the problem … seems to have gone away. My best guess is that Time Warner’s router keeps flushing its ARP table and “inactive” connections (if you haven’t opened a web page, or typed something in the terminal in the past N minutes) get dropped. By keeping the connection perpetually active, I avoid being dropped.

A somewhat hackish solution, but it beats complaining about the crappy service.

Posted by distler at December 8, 2005 11:53 PM

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9 Comments & 0 Trackbacks

Re: Cable Fun

For whatever it’s worth, I’ve got Grande, and my cable modem really did just crap out suddenly. Fine connection one minute, no power light the next.

Posted by: Adam Rice on December 9, 2005 10:26 AM | Permalink | Reply to this

Re: Cable Fun

I had similar issues with Cox cable. After calling for two weeks (and having a new line run to the house) a technician noticed that my modem was an older model that was no longer supported. I bought a new modem and haven’t had a problem since.

Posted by: Ryan on December 9, 2005 12:57 PM | Permalink | Reply to this

Standards

Was your “old” modem a proprietary one, or was it a DOCSIS modem? In theory, at least, the point of having a Standard is that any DOCSIS-certified modem ought to work. Mine’s a Toshiba PCX 1100, which, albeit rather old, is DOCSIS-certified.

Posted by: Jacques Distler on December 9, 2005 4:00 PM | Permalink | PGP Sig | Reply to this

Re: Cable Fun

When I was living just north of campus, we had tons of problems with TWRR. After innumerable exasperating service calls and escalating higher-level techs, most of it was traced to bad wiring, layer upon ancient layer of garbage. Techs took shortcuts with splitters, wires run across open roofs, BNC connectors loosen from the coax, and time, UV, and rain will cause spontaneous and intermittent signal degredation.

You can ping the nearest TWRR router instead of golumn (use traceroute to identify it), which may tell you if the problems are in the copper from the poles, or in TW’s own network.

The ARP explanation sounds unlikely, whereas RR is known to have occasional routing and peering problems.

-Alex (UT Physics 2001, UCSD gradstudent)

Posted by: Alex Winbow on December 9, 2005 5:52 PM | Permalink | Reply to this

Re: Cable Fun

Are you using ssh for your terminal sessions? That ought to be doing periodic keepalives. If so, I’d be suspicious about whether it’s a timeout issue.

I’m on my third cable modem in two years. They do go bad. (Cheap consumer-grade crap.) It may be the most unreliable part of the network.

Posted by: chip on December 9, 2005 8:22 PM | Permalink | Reply to this

Re: Cable Fun

Sometimes SSH, mostly SRP Telnet. And, no, it’s not the terminal session timing out, it’s the whole damned internet connection.

Alex wrote:

You can ping the nearest TWRR router instead of golumn (use traceroute to identify it), which may tell you if the problems are in the copper from the poles, or in TW’s own network.

The ARP explanation sounds unlikely, whereas RR is known to have occasional routing and peering problems.

Pinging any of the intermediate routers fails as well. The problem is somwhere between me and the nearest router. It could be at the router (as per my ARP table explanation) or it could be at the CTMS (and whatever it uses to keep track of active cable modems on its HFC network segment).

But whichever it is, simply sending a regular stream of ping packets upstream keeps my connection alive.

Posted by: Jacques Distler on December 9, 2005 8:49 PM | Permalink | PGP Sig | Reply to this

Re: Cable Fun

I had the same problem with Time Warner days ago, but now everything goes to normal. Can it be a temporary problem of the network but not the “inactive” policy by TW? It’s weird that one of my friends who use SBC had the same problem at almost the same time.

Posted by: Hui on December 12, 2005 2:39 PM | Permalink | Reply to this

Re: Cable Fun

Responding solely to your musings about cable modems failing, I had some big trouble here in River City (Austin) back in August. My modem was part of the trouble. My suspicion is that the intense thunderstorms around that period did the job of screwing it up in weird ways. I documented it how TW got it fixed-up .

Posted by: Travis on December 28, 2005 2:02 PM | Permalink | Reply to this

Re: Cable Fun

I’ve had similar problems with Time Warner, distler. Overall as a company, they do not seem to give a valiant effort in customer service or ensuring satisfaction. With all of the issues (I also had to swap modems) it came to a point where I just had to walk away. I’m glad you found a solution that worked for you.

@chip - I’ve had problems with my modems in the past, so I back up your theory that they do go bad. That, or I’m the unluckiest guy when it comes to internet connection!

Posted by: Trevor on October 26, 2010 9:30 AM | Permalink | Reply to this

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