Common operational misconceptions

Tue Feb 21 02:07:20 UTC 2012

On Sat, Feb 18, 2012 at 1:19 AM, Bob Vaughan <techie at w6yx.stanford.edu> wrote:
> "Ethernet/Token Ring/Cisco Console/whatever uses an RJ45 connector"
>  RJ45 defines a keyed 8P8C type connector, wired in a specific
>  manner, for a specific 2 wire telco service. Incompatible with the
>  above on several levels.  "RJxx" == specific connector/wiring pattern
>  for specific telco applications. Non-telco uses need not apply.

RJ45 is really an example of what was originally a misconception
became so widespread, so universal, that reality has actually shifted
so the misconception became reality.   When was the last time you ever
heard anyone say "8P8C connector?"

Joe public caught on to "RJ45",  so now that word means something
different in common usage than what it was specified to be.     When
was the last time you heard someone say 8P8C connector in reference to
Ethernet?

Nowadays it is technically ambiguous to say "RJ45";  are you talking about
[a] The original standard, Registered Jack 45,  which was a specific
connector together with a specific pinout   (which is not Ethernet
over UTP)?     Usage of the connector is exceedingly rare,  and will
hardly ever be referred to.

Or
[b] "Ethernet" connector; The generic 8P8C connector (which has a
certain resemblance to RJ 45) is specified for use with TIA/EIA 568
compliant cable termination ?

Now instead of [a]  being  correct and [b] being always the
misconception.....     [b] is "correct" in common usage.

And you have to decide based on context of the conversation which
defintion of RJ45 is intended,  but  [b] will almost always be the
correct definition.

--
-JH