diagnosing network speed bottlenecks

[Tom Buskey]

On Wed, Sep 30, 2009 at 1:36 AM, Greg Rundlett (freephile) <
greg at freephile.com> wrote:

>
> 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
>

Definitely.  I have FiOS and find many sites just don't keep up.  When a new
version of Solaris comes out, sun.com used to let me download 4 DVDs at the
same tie, flat out.  They now throttle the number and speed.


> 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.
>

WTF?  Newer tech will allow faster rates, but the old tech should still run
at the same speed.  That speed may be lower then the new rate which might be
what they think they're talking about.  This sounds like a Joe Sixpack
explanation.


> c) that my network speed is shared by all the devices on my network so
> that could affect my observed speed
>

All your devices go through your router.  The router can only process
packets so fast.  I you test with multiple devices, you degrade the test.
Again, Joe Sixpack who doesn't use scientific methods.

The CPU in your router will affect your maximum speed.  I know a PIII will
not keep up with Gigabit ethernet.  My system topped out at 30 MB/s where my
AMD X2 will do 60 MB/s which is about the max.  I have seen 80 MB/s on a
high end Sun.

100 Mbit ethernet will top out at 11.2 MB/s.  If your router isn't gigabit
ethernet to the rest of your network, you're not going to get faster then
that.  I think most cable modems are 100T.  I know my FiOS is.

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.
>

Wireless is 54 mb/s.  100T is 100 mb/s.  You're never going to get more then
11.2 MB/s through it on the wire and  ~ 5 MB/s on 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
>

Right.


> 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
> -skype/aim/irc/twitter freephile
> http://profiles.aim.com/freephile
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