[GRLUG] Speed loss

[Michael Mol]

On 05/01/2013 10:55 PM, Bob Kline wrote:
> Since I brought up the issue of losing 
> bandwidth for the last 4 or 5 days, let
> me add just a bit.  The downstream 
> bandwidth, using the speedtest.net <http://speedtest.net> 
> Detroit test point, hosted by Comcast,
> has degraded by about 35%, and still
> seemed to be going down. The upstream
> bandwidth was more or less unchanged.
> 
> What to do?  Why, power cycle!  I mean,
> why not?  What can it hurt?
> 
> Doing that, everything came back, and
> the bit rates up and down are what they
> were a week ago.
> 
> So,  how come?  Other than the fact 
> that power cycling cured what was ailing
> the bit rate, why should I have needed 
> to do this at all? Something to do with
> the modems interaction with Comcast?
> 
> Just curious.  In the end I'll have to 
> power cycle in any case in the bandwidth
> sags again, but if anyone has any thoughts
> about this, please post them.

There are a number of things that can get crufty in network equipment if
they're not configured properly. Since it seems most consumer network
equipment runs Linux, it also seems likely manufacturers don't change
defaults much...and there are things (such as how long to assume
connections are open) with insanely long timeouts. Like five *days*.

I've got a thought that the problem may not be with the modem, but with
the router's routing tables and other cached information. Powering off
the modem would look like a link drop to the router, leading it to do
some internal cleanup and garbage collection.

A couple things to try in the future:

1) Unplug the network cable, wait 15-30 seconds, plug it back in.
2) Unplug the router, wait 15-30 second, plug it back in.

Both are ways of testing that theory.


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