[GTALUG] war story: bad ADSL packet loss

D. Hugh Redelmeier hugh at mimosa.com
Mon Jan 5 23:46:10 UTC 2015

My internet connections are confusing and complicated so I will spare you 
those details.

One connection is via ADSL2 to telnetcommunications.com.  It started
to get flaky.  I measured 50-90% packet loss over various periods of

I also have a VDSL2 connection with telnetcommunications.com that did
not have the problem.  Tentative conclusion:
telnetcommunications.com's network is not the problem.

I use a TP-Link TD-8816 as a modem, but not as a router.  I have a
Linux box that does the PPPoE thing.

I tried: powercycling things, one at a time, to see if things got
better.  They didn't.

I tried: phoning support.  They suggested switching phone cable or
ethernet cable before trying to talk to Bell.

I tried: switching cables.  No change.

I tried: taking other phones off phone line and removing splitter
where the ADSL modem was connected to the wall jack.  No change.

I tried: swapping ADSL modem for an identical one, purchased at the
same time.  It worked!

Lesson's learned:

- being a hoarder has its advantages (why did I buy two ADSL modems 3.5
  years ago?)

- being a hoarder has its disadvantages.  Both modems are out of (2
  year) warranty.  The splitter that came with the newly unwrapped
  modem doesn't work and I have no recourse.

- ADSL modems sometimes fail.  My previous ADSL modem (Speedstream
  something or other) failed, but I don't remember the symptoms.

- ADSL modems don't always fail hard.

- with so many pluggable parts, there is a very large number of
  configurations to test.  The modem has: power, phone, ethernet,
  all of which could have been swapped.  The wall jack needs
  a splitter, an ADSL filter on one side, and cables connecting all
  of these.  Of the right length.  And other jacks in the house need
  to be played with too.

  I didn't even bother to see if the replacement modem would work as
  well with the original modem's power supply, or vice versa.  Life's
  too short.

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