[ale] Monitor Internet Traffic

[Michael B. Trausch]

On Wed, 2015-08-12 at 14:01 -0400, Chris Fowler wrote:
> I have a TP-LINK ADSL2+ dual-band wireless router.  It offers me no
> features to monitor traffic.  I'm thinking about buying a ADSL2+
> bridge at Frys and then tapping the CAT-5 from it to the TP-LINK to
> sniff.  Are there any good Linux packages to do this?  Something I
> could run on the Pi2?
> 
> I'll use DHCP to statically assign each device in the house with an
> ip address.  I will then look at traffic based on IP.  I'm trying to
> get an idea of how much bandwidth we are using and when so that when
> I need it most I can throttle it down.  I'll know where it is coming
> from.
An RPi2 should be fine—using the built-in Ethernet and one extra USB<
->Ethernet dongle, as long as the throughput you're attempting to
measure won't exceed approximately 120 Mbps across the bridge.  (The
limit comes from the Ethernet being attached to the system processor
via USB.)
If you wish to exceed that limit, use a PC with PCI-E attached 2x GbE
or 4x GbE interfaces, and ensure that you have 2 cores which are at
least 1.2 GHz.  General rule of thumb is to have ~1MHz processing power
for each Mbps on each interface that you'll handle.  Virtually any
system available should fit that bill, as long as it has a sufficient
internal backplane.  Obviously you would invalidate the effort of using
a PC if you still resort to USB Ethernet devices.
Note: I am assuming USB 2 since that's all that's on the Pi units and
similar SBCs.  However, if you have a small multicore device that has
USB 3, it might be usable for high-speed processing on a transparent
bridge.
	— Mike
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