In a short channel, e.g. a 1" long Ethernet cable, which effects are most likely to reduce throughput and why? What would the nature of the throughput reduction be? Specifically, I am wondering about 100/1000 Mbps Ethernet over standard cables like CAT5/5e/6/etc. My assumption is the error rate will jump significantly as the transmission line crosses a threshold that we could colloquially call "too short," but I am unable to quantify that in a meaningful way.

I've been researching this and I'm not finding a lot of relevant information. This paper has some interesting information, but the low-level dive into signals and EM fields is beyond the scope of the topic it seems.

I'm thinking there are a few potential issues:

  • Fractional wavelength issues due to the transmission line length
  • Timing (min time violations if such a thing exists in this context)
  • Power (saturating the receiver)
  • ISI (reflections)

I'm sure there are others and maybe the issues I've listed aren't relevant. Any information would be greatly appreciated.

  • \$\begingroup\$ Isn't an electrically short cable equivalent to a longer cable carrying a lower-frequency signal? I'm not sure why you'd expect there to be a higher error rate when reflections, etc. would die down much faster than with a longer line. Keeping data lines short is usually considered good design, not a risk factor. \$\endgroup\$
    – Adam Haun
    Aug 2, 2018 at 2:00
  • 1
    \$\begingroup\$ I proposed multiple ways this could be bad aside from strictly electrical issues. I’m asking for discussion about particular points that lead to an objective conclusion regardless of whether or not the original supposition is true. I have observed reduced throughout in short channels with no apparent differences other than channel length when compared to higher throughout channels. I would like to know why that happened and which theoretical issues could have caused it. \$\endgroup\$
    – Anthony
    Aug 2, 2018 at 4:03
  • \$\begingroup\$ This isn't a discussion site it's a Q&A site. If you want discussions you might be in the wrong place. \$\endgroup\$
    – Andy aka
    Aug 2, 2018 at 7:32
  • \$\begingroup\$ The biggest problem with a one inch cable would be plugging it into two sockets. \$\endgroup\$ Aug 2, 2018 at 8:02


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