How to implement TDR in software?
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Posted by Dmitri(Cabling-Design.com on August 29, 2005, 3:29 pm
Please log in for more thread options James Knott wrote: > As far as I know, there's no way to create a TDR, with a standard NIC.
Well, the Alaska chipset by Marvell was going to support that functionality that's well beyond the reach for an ordinary NIC card. On the other hand, Alaska is a Gigabit chipset, so it's bound to have much more circuitry to deal with both near-end and far-end cross-talk, which makes it few steps closer to being able to actually test the cable than your regular 2-pair 10/100 NIC. This chipset first surfaced about a year ago here: http://www.cabling-design.com/forums/Virtual-Cable-Tester-Technology-article491-21.htm However, all attempts to get my hands around a mobo or a NIC with Alaska chipset to date have failed. Several times I have specifically seek out a part with Alaska chipset in the specs and every time I've gotten a Realtec's chipset instead. So, I have all reasons to suspect that Virtual Cable Tester technology, although sounds very interesting indeed, is not easy to implement, and the manufacturer has all kinds of problems with production as well. With that said, I would be glad to hear from someone who was able to get that elusive Alaska. Any real-life feedback will be greatly appreciated! -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 2340 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||||||||
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Posted by James Knott on August 29, 2005, 12:24 pm
Please log in for more thread options Dmitri(Cabling-Design.com wrote: > James Knott wrote:
> >> As far as I know, there's no way to create a TDR, with a standard NIC.
>
> Well, the Alaska chipset by Marvell was going to support that > functionality that's well beyond the reach for an ordinary NIC card. On > the other hand, Alaska is a Gigabit chipset, so it's bound to have much > more circuitry to deal with both near-end and far-end cross-talk, which > makes it few steps closer to being able to actually test the cable than > your regular 2-pair 10/100 NIC. According to what I saw there, it simply adds some diagnostics to the NIC, which is still a long way from being a TDR. For example, can that chip tell you the distance to a short or open? | |||||||||||||||||||||||||||||||||||||
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Posted by Dmitri(Cabling-Design.com on August 29, 2005, 6:23 pm
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James Knott wrote: > According to what I saw there, it simply adds some diagnostics to the
> NIC, > which is still a long way from being a TDR. For example, can that chip > tell you the distance to a short or open? My understanding was that they give you exactly that, the distance to short/open but not much else. So, of course it is not a good TDR, but if this function were there, it would have been a very nice addition to the network admin's toolbox indeed. Below is a quote from that whitepaper: <quote>
Upon installation of a Gigabit switch, the IT manager finds that
all Gigabit ports are functioning with the exception of the fourth port. He/she then sees through the switch software interface a “pop-up” message that reads: “Network connection has failed on Port 4. Pair 2 (typically pins 3 and 6, orange color) of your CAT 5 cable is discontinuous (“open”) approximately 68 meters from the switch.” The IT manager is then able to make the repair to the cabling plant and all ports of the switch operate flawlessly at Gigabit speeds. The engine behind the above software pop-up message is Marvell’s VCT technology. </quote>
Once again, I don't think the technology is quite there outside the lab yet. I was not able to procure a NIC or a mobo that was said to have an Alaska single-port transciever and I'm not aware of a switch using a multi-port version of it either. -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 2344 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||||||||
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Posted by NANewbie on August 30, 2005, 7:49 am
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As we know the whole TDR concept involves 1) sending a signal down a cable, 2) waiting for its return, 3) taking the time difference, 4) and calculating the distance. Does a standard NIC allow itself to be configured to send an electrical signal down a cable? Is there a standard way to trigger an NIC (regardless of brand) to send a signal? I was thinking, if it's possible to write a program to achieve 1) and it's guaranteed that the signal would get reflected either at a fault or end of cable, then the rest would not be a problem. ------------------------------------- James Knott wrote: > NANewbie wrote:
>> Hi!
>> >> I wonder if anyone can help me understand something. I've just >> read the >> whitepaper about the VCT Technology by Marvell and the TDR >> technique used. >> I was just wondering, how did they implemented TDR in software? >> Did they >> manufacture the NIC in such a way that it acts as a reflectometer >> or did >> they program it? If it's the latter, how is that possible? > As far as I know, there's no way to create a TDR, with a standard NIC.
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Posted by James Knott on August 30, 2005, 8:33 am
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NANewbie wrote: > Does a standard NIC allow itself to be configured to send an electrical
> signal down a cable? Is there a standard way to trigger an NIC > (regardless of brand) to send a signal? I was thinking, if it's possible > to write a program to achieve 1) and it's guaranteed that the signal would > get reflected either at a fault or end of cable, then the rest would not > be a problem. A NIC has to send a signal to transmit. However, there's more to a TDR to that. Generally, you send a pulse down the wire and measure the echo characteristics. It's the measuring of the echo that's the hard part. | |||||||||||||||||||||||||||||||||||||
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