The Worm in the Machine

The home network situation remains somewhat weird. Last Friday, Bellsouth’s Indian outsourced tech support promised to ship me a filter to make the new modem go, one that they had neglected to include in the original packet. They swore it would go out Monday and arrive Tuesday. It did not, and the tracking number they provided when I called to complain made it clear that it didn’t leave their hands until Tuesday morning. The Indian help desk line person was amazing Tuesday night, though, and kept insisting that his computer had better access to the United States Postal Service computer than mine did, and his display showed it had shipped Monday.

So after that fruitless and frustrating telephone experience I thought I’d try the network again. Friday morning I’d turned everything off and let it cool down. Friday night I’d turned it all on again but it remained dead as a post – couldn’t even reach the router. I’d left it all on since then…but Tuesday night I discovered it was working again once I resaved the router’s login info, which had been erased by the hard reboot. Had the Alcatel 1000 risen from the dead? Was it the router? Or was it an upstream issue after all? I had no idea, but who cared so long as it worked… In an abundance of caution, I turned of all logging on the Linksys router — even though it has been on for months — as I’d read that my version of the firmware got unstable sometimes with any logging tunred on.

And so all went fine … until this evening when one of the kids fired up the family room computer and found that it could not access the internet. Oddly, and differently from the earlier symptoms, the other computers in the house still could. Was this a different problem or a symptom of the same one? Was it relevant that the last thing he’d done was to start up the Stagecoach Island download?

I did my usual round of diagnostics. IPCONFIG /ALL showed normal. Ping was dead. Other computers on the network were fine. We rebooted. No change. But I’d noticed that this machine, unlike the others in the house, didn’t have Microsoft’s IPv6 implementation even though it is running Win XP (Sp2) (dual booting with SUSE 10, but that’s another story). So, grasping at straws, I installed IPv6. And immediately it was happy again, without even rebooting.

I find that odd — as I understand it, IPv6 is supposed to co-exist happily with IPv4. And the router is old enough not to expect IPv6 anyway. I’ve rummaged around a little online and haven’t found anything that speaks to this problem, which may mean it is just a coincidence.

But my search did disclose the some mundane facts and one delightful one: It seems that Win XP uses its own IPv6 implementation rather than the standard one called 6to4. The Windows version is called Teredo tunneling. Indeed it was seeing the references to a Teredo tunneling adapter on my computer plus some DNS gunk of the form fec0:0:0:ffff::1%1 fec0:0:0:ffff::2%1 fec0:0:0:ffff::3%1 which put me on to this issue in the first place: On investigation that gunk proved to be an IPv4-encoded IPv6 address … whose absence elsewhere later alerted me to the absence of IPv6 from the family room machine.

So here at last is the delightful fact, straight from the Wikipedia:

The initial nickname of the teredo tunneling protocol was shipworm. The idea was that the protocol would pierce holes through NAT, much like the shipworms bore tunnels through wood. Shipworms are pretty nasty animals, responsible for the loss of very many wooden hulls, but Christian Huitema in the original draft noted that the animal only survives in relatively clean and unpolluted water; its recent comeback in several Northern American harbors is a testimony to their newly retrieved cleanliness. Similarly, by piercing holes through NAT, the service would contribute to a newly retrieved transparency of the Internet.

Christian Huitema works for Microsoft, and was obviously pressed by Microsoft’s public relations to pick a slightly less offensive name. Teredo navalis is the latin name of one of the best known species of shipworm. At least, the name Teredo does not immediately evoke computer worms.

Gotta love it. And, it seems (maybe), gotta have it too.

Meanwhile, the DSL modem line filter has arrived — a day late — but I haven’t yet installed it, or re-installed the ‘new’ Westell modem. If it ain’t broke…

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3 Responses to The Worm in the Machine

  1. Bruce says:

    Interesting. We had a Westell DSL modem/router at our last apartment, and had off-again, on-again, really-slow-again service, with no correlations that I could determine. No one at Verizon ever suggested the *modem* needed a filter, just the voice lines (which suffered greatly from static and modem-like noises, even with the filters installed). Maybe Verizon had it backwards and the Westell needed the filter, not the voice lines?

  2. Michael says:

    The westell modem uses a special split filter, with one jack one for the DSL modem, and one for a phone. Other devices plugged into other phone jacks in the house are supposed to use the regular telephone filters.

  3. dilbert dogbert says:

    My brother in law installed dsl in his place and had a noisy line no matter what he did or the phone co, pacbell/sbc did. Finally someone at pacbell remembered that they had installed some gear years ago that had not been removed. On removal everything worked.
    When the bro in law gets back from the cruise i will ask him what the equipment was called. Someone else my have the same problem and has given up on dsl. There are a lot of ways to screw up dsl.

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