Ethernet sniffer processing? Just an idea.

[mindctrl]

Hi,

I was thinking the other day... I would like to do a project that is small, has two RJ-45 ports (one labeled input, the other labeled output), and then a PIC between the two. You plug this into an ethernet line, let's say between a router and a switch so all the packets that are destined for the router (anything traveling on the cable) hits the PIC. Could you possibly make a PIC that sniffs for certain words in an ethernet packet? I know this is probably a very complicated process (I am a CCNA, so I know my TCP/IP stacks), and I was just wondering if something could handle it. Does anybody know of a project that is similar?

Thanks for the input.

--mindctrl

 

[kybert]

The fastest PICs are 20MHz, as the slowest ethernet is 10Mbps, you may have trouble capturing the data, and even if you did capture it, you'd not have enough overhead in the PIC to process it before the next lot arrived.

You'll need to use a much faster device.

 

[pittuck]

WEll the fastest pics are now 48Mhz, but u still only getting 3 or 4 instructions between bits, I suppose u could use a 48Mhz chip and then use a nother at same speed on a parralel connection and a interupt line, giving u about 30 instructions between bytes in.

Not a lot of time, u gonna need upwards of 150Mhz to get enough room to do this sort of processing. I also suspect it to be highly illegal in some parts... [well depending on how its used]

 

[checkmate]

48MHz only gives you 12MIPs. At 10Mbps (assuming an ultra old system all using 10BaseT), that's 1.2 instructions per bit.
Most hardware protocol analyzers often involve large amounts of RAM to handle the high datarates.

 

[pittuck]

bleep, lol

forgot that

 

[bmcculla]

This sounds like a task for a 32 bit processor. With a little searching I'd bet you could find a ARM processor with a built in Ethernet MAC. Then all you need is an Ethernet PHY.

If you wanted a device that would just "sniff" the data as it passed you might have to build a modified MAC in an FPGA. Spartan 3 FPGAs are fairly inexpensive - Avnet has them in stock off and on. Depending on the size of your FPGA you might be able to fit a soft microcontroller core on it too. OpenCores.com has a bunch of free cores available.

 

[mindctrl]

FPGA? Never heard of one. Could I get some more information on those? Thanks for the help.

 

[bmcculla]

FPGAs let you build your own digital logic devices. You program in gates and flipflops to make up a custom digital circuit. The two biggest manufacturers are Xlinx and Altera. Their web sites will give you more info.