TDR function in Cisco routers.

[SN]

Does anyone have intimate knowledge of the characteristic and timeline of pulses sent from the port of a Cisco router or switch during their built-in TDR test function? 

I expect this is proprietary information and won't be outlined in any technical manual Cisco publishes. 

It sounds like similar functions are now available from other manufacturer in recent years, so maybe there is more public knowledge available than what I've been able to find online.

Thanks in advance!

[madires]

I don't think any vendor will publish signal details of their TDR function for Ethernet ports. But a DSO might give you an answer.

[SN]

Yes.  I certainly plan on getting a capture for myself at some point.  I am also wondering if other router manufacturers have basically standardized on a signal scheme for TDR functions or if they're all doing their own thing.  If I read it right, Cisco requires about 5 seconds per port to run the test.  I assume a great deal of that time is for processing/analysis.

[alm]

I've seen PC motherboards that also incorporate a TDR function. For example using this IC. There is some information here and here. TI also has an application note on TDR using Ethernet transceivers.

[coppice]

Isn't cable measurement a standard part of the echo cancelling function for gigabit ethernet and above?

[SN]

I've seen PC motherboards that also incorporate a TDR function. For example using this IC. There is some information here and here. TI also has an application note on TDR using Ethernet transceivers.

That's exactly the kind of information I was looking for.  Marvel's documentation expresses this function as "Virtual Cable Tester" and it seems to be a registered trade name.  Thanks!

[madires]

Isn't cable measurement a standard part of the echo cancelling function for gigabit ethernet and above?

Each side sends training sequences to learn how the echo looks like, to determine what to expect as echo when sending data. If the echo is different then the other side is also sending data. The other's side data is the difference between the expected echo and the received echo.

[SN]

Thanks to ALM for turning me to TI's site! 

While browsing, I found a slightly newer Application Note for working with TI's built-in TDR function.

https://www.ti.com/lit/an/snla330/snla330.pdf?ts=1714855065817&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDP83825I