🚀 go-pugleaf

I normally connect to the Internet via a Comcast residential service 
with the following physical devices in the chain:

   MacBook (10.4.11) --- Airport Extreme base station ====
   Comcast-provided modem (a Motorola "Surfboard") +++ (outside world)

where --- is an Airport WiFI link; === is Cat 45 Ethernet cable; and +++ 
is a Comcast cable coming from the street.  We also have Comcast VOIP 
service for 4 or 5 telephone lines which I believe connected into the 
+++ cable somewhere upstream from the Comcast modem.

All of this work great the majority of the time, but there have been two 
service outages during the past month when Internet and phone service 
went down for 4 to 8 hours.  In  the most recent case,  the phone came 
back up after a few hours, but the Internet connectivity remained out 
for several more hours.

The JPEGs at <http://www.stanford.edu/~siegman/Comcast1.jpg> 
and <http://www.stanford.edu/~siegman/Comcast2.jpg> show what I see at 
different times, using the Network pane in the Mac's System Preferences 
as a way of attempting to diagnose whether the outage means something is 
wrong in my local settings or hardware, or Comcast is really down.

I'd appreciate any tutoring on what these are telling me -- notably, 
what and where is the "ISP" element in this chain, which seems to remain 
green all during these outages?  

My naive understanding is that ISP means and "Internet Service Provider" 
-- presumably, some computer located out in a Comcast building 
somewhere.  So, are these lights telling me that I'm in fact 
communicating OK all the way to this Comcast computer, over the Comcast 
cable -- but that this computer is somehow unable to handle my traffic 
or link me onward to the Internet itself?

Any educational assistance appreciated.