[Tfug] Patch cords

[Bexley Hall]

Hi Bender,

--- On Sun, 9/30/12, Bender <bender at bendertherobot.com> wrote:

> Have you seen the kind of cables people make by hand?

Actually, no.  The only cables I've seen are store-bought
cables and the ones I've made myself.  :<

> Some people lack the dexterity and patience it takes to:
> 
> Strip the outer jacket without nicking inner wire insulation
> 
> Get all of the wires crammed into the connector fully *while*
> maintaining the proper order of the color code *and* making
> sure the outer jacket is sufficiently shoved into the
> connnector so the jacket crimp can hold.
> 
> I have seen more than a few cables terminated with 1-3
> inches of outer jacket removed - conductors 1-2 & 3-6
> inserted and either the rest of the conductors remaining, or
> cut off entirely. And, the conductors used had no twist for
> that 1-3 inches of exposure.

If the admonition against making cables is due to *incompetence*,
I could buy it.  I wouldn't advise "just anyone" to:
- solder two wires together
- rework a SMT board
- sweat a pipe
- mat a painting
- wire an electrical outlet
- change the brakes on their vehicle
- bake a cake
- frame a window
- operate a power tool
etc.

OTOH, I know many folks that I would have no qualms describing
how to do each of these things and have a high degree of confidence
that they will obtain successful results without me standing over
their shoulder.  Its a matter of having tools "appropriate" to
their abilities and abilities appropriate to the task at hand!

The folks who have (historically) advised me against this are
aware of my abilities, tools, experience, "attitude", etc.  I.e.,
they know I can:
- reball a BGA
- fabricate flex circuits
- build SMT prototypes

So, I suspect something more than "competence" lies at the root
of their "discouragements".  I.e., perhaps the relatively high
cost of recognizing and troubleshooting a failing cable at an
arbitrary point in the network fabric.  Especially when you have
other "responsibilities" that you are supposed to be addressing
("Hey, Bob, how come the new server hasn't been swapped in, yet?")
 
> A ratcheting crimping tool is preferred especially when you
> are going to be doing that many. Otherwise when you get
> tired, you might not be so inclined to press the handles
> down fully.
> 
> If you prepare, assemble and crimp with appropriate
> conectors for the type of cable you are using, it's not
> rocket science. (especially if you use a cable tester to
> verify pairing and continuity (at minimum))
> 
> However, people have been burned often enough so they avoid
> home-made cables for good reason.
> 
> It's not for everybody, especially when you can get
> pre-built cables with strain relief boots in 0.5', 1', 2',
> 3', 5', lengths for around a buck and 7', 10', 14', 20',
> lengths for $2-$3 (plus shipping)

For a data center, you can handle the "slop" that an oversized
cord carries with it.  If you use a 7' cord where a 5.5' cord
would have been ideal, you can find someplace to "hide" the
extra 18 inches (in a cable tray or an extra long service loop
on one -- or both -- end of the cable).

OTOH, if all your routes are in the 1-4 ft range, having only
12 inch increments to choose from (lets pretend the 5' standard
length is really 4'), then, on average, you have 6 inches of
slop PER CABLE to deal with.  In a span that is 1' to 4' long.

So, 70+ of these mean you've got 35+ feet of "slop" to deal with.
In a very small space/volume (recall, this isn't a data center).
And, that 35' isn't in one nice, convenient piece that you could
coil up and hang on a peg!  Instead, it makes the rats nest
"bulkier".

Think about how *you* would handle something like this in your
present home.  Imagine a 72 port patch panel.  And three 24 port
switches.  The "easy" solution is to stack the three switches
and put the patch panel above/below.  Then, one-to-one wire
the panel to the switches.

But, now you've taken a chunk of space as wide and deep as the
switches and ~16 inches tall.  Can't put anything *behind* this
(because the wires that the patch panel services have to come
in from somewhere -- and anything behind the switches would be
hard to access).  And, anything in front of it would have to
be moved any time you needed to access a switch or the patch
panel.  You would also need to have that (front-to-back) depth
available in order to locate things in front or behind.

Now imagine individual patch panel ports have specific switch
ports to which they need to be routed.  E.g., maybe all the
ports on the left side of the panel need to be routed to
the second switch while those on the right get routed to the
third switch -- and the balance go to the first switch.  Now,
cables aren't all the same uniform length.  They criss-cross
in front of the switches as they each fight to get to their
respective destinations.

Then, add an extra 35 ft of wire to the rats nest...

If I had a spare room (or a basement!) this would be a no-brainer!
 
> see the link Harry posted...