A munin plugin for monitoring cable modem performance

A couple days ago, a brief IRC discussion ensued on the topic of cable modems, oversubscription, power levels, etc. Someone mentioned that they noticed their transmit power level increasing during peak hours, perhaps due to heavier traffic. I thought this dubious, but I had no evidence to prove otherwise. A short bit of code-pounding later, and behold: a Munin plugin (written, comfortingly, in Python) to plot essential cable modem data. This totally won't work with anything other than the exact Ambit cable modem I have here (on Time Warner Cable's RoadRunner network in Rochester, New York), but it is here to serve as inspiration: if you can get at the data, you can plot it! I am currently plotting:

• Downstream Frequency
• Downstream Receive Power Level
• Downstream SNR
• Downstream Symbol Rate
• Upstream Frequency
• Upstream Symbol Rate
• Upstream transmit Power Level

So far, I'm noticing that the frequencies change a few times per day: as of this writing, since midnight, the downstream and upstream frequencies have both changed five times. Also, the upstream power level stays fairly constant (although it did make a big jump around 8:30am), but the downstream power level bounces around a lot. (Not too surprised.) The weird things, though, are the little "blips" in the signal to noise ratio. Time will tell, I suppose. (updated 2009/07/29: source is now hosted on github)