I'm in the middle of a project that requires writing software that would send some packets over Ethernet every N milliseconds. The ethernet wire would go from a computer to a switch, and then to the rest of the network. There is no back-traffic, so packet only go out, nothing goes in. This "idealized" situation was created to measure jitter (time variability) of the packets. For example, even though we expect a packet to go out every 5ms, it will actually leave the computer every 5ms +- w where w is random uncertainty (i.e. jitter).
I would like to measure this jitter by hooking a scope to the internal wires of an Ethernet extension adapter, recording the waveform and looking at when bursts of data (packets) are transmitted. I'm making lots of naïve assumptions about Ethernet in general and CAT5 specifically, and so far I'm failing to see anything meaningful except of every possible flavor of noise. Therefore, I have questions.
First of all, can I even assume that no signals other than my packets are constantly being transferred back and forth between my laptop and the switch?
Secondly, does my probing scheme work at all? Can I simply connect two CAT5 wires with such adapter, break it open, strip insulation off wires and hook them to a scope? If yes, which wires should I be looking at?
Finally, can my 100MHz scope even handle the stuff that will be sent over my 100 Megabit connection? I only need to see whether a burst is present or not, so I thought it would be fine.
Are there any other suggestions on how I may do this alternatively?
Cheers! = )