diagnosing network speed bottlenecks

[greg-SfI3QVg0eaJl57MIdRCFDg at public.gmane.org (Greg Rundlett (freephile))]

I'm not a network packet-sniffing blood-hound, so I need some help of
the mere-mortal variety :-)

I'm generally dis-satisfied with the speed of my Comcast "High Speed"
Internet connection.  It's touted on the tele as being some
ambiguously huge amount faster than light travels in a vacuum.

The service that I have costs $42.95 per month and advertises
"Downloads up to 15Mbps, uploads up to 3Mbps with PowerBoost" (which
is inflated due to the fuzzy math they use around the temporary boost
they allow on the first xMB of a transfer, and depends on the
equipment you have*).  Now Comcast is offering tiered services of
Internet (the highest depending on a DOCSISv3 modem).  Their 'economy'
service is the only service that is cheaper, while there are three
plans that are more expensive -- up to $99/mo. for Internet service.
http://www.comcast.com/shop/buyflow2/products.cspx (can't access page
without giving your address)

Speed tests like http://www.dslreports.com/speedtest?flash=1 report my
performance as...
4,909 Kb/s Download
3,055 Kb/s Upload

But, in my experience downloading files, I rarely get anything like
that.   In fact, while the DSL Reports Speed Test is checking my
system, I'm watching the "Network History" graph on the "Resources"
tab of System Monitor (v2.26.0.1) aka gnome-system-monitor and it's
not breaking 800Kbps.  I then used wget to download MySQL Workbench
and it reports 33,373,104 downloaded in ~42 seconds at a rate of 783
KB/s

When I called them to inquire why my speeds don't seem to stack up to
the service - they offered three explanations...
a) that sites that I'm using will and do control how fast they will
allow me to download from them and
b) that my router could be the culprit because they generally wear out
after two years, and I should buy a new 'draft-N' router.
c) that my network speed is shared by all the devices on my network so
that could affect my observed speed

a) while sites do limit bandwidth allocated to a single user, I don't
think this will be the case all the time.  Anyone know of a site that
doesn't throttle which would allow me to eliminate a)
b) I have a U.S. Robotics 802.11g router currently and I'm open to
opinions on whether I should replace it, or test it's capacity.
c) I have 6 DHCP clients on the router (none windows), and nobody is
awake right now but me, so those clients can't possibly be hogging all
my bandwidth.  I just installed ntop and I'm collecting some stats,
but it doesn't look like there's too much "latent" activity on my LAN.
 The peak load in the last 5 minutes was 8.9 Kbit/s

Note too: I have a wired CAT5 connection, although other devices use wireless.

* I have a DOCSISv2 modem (the Arris TM602g)
http://www.productwiki.com/arris-tm602g/  -- a new model supplied when
I recently signed up for their bundled service of Internet, Phone and
Cable.  According to
http://en.wikipedia.org/wiki/List_of_device_bandwidths#Modems.2Fbroadband_connections,
the DOCSISv2 standard means the modem is only capable of 4,750/3,375
kB/s speeds, which means it will never get to "15 MB/s" that they
advertise.  According to the product data sheet, the max data rate
down is 30 or 42 Mbps which equals 3.75 - 5.25 MB/s

Greg Rundlett

nbpt 978-225-8302
m. 978-764-4424
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http://profiles.aim.com/freephile