
Is Your Cat 6 Cable a Dog? (2013) - handedness
http://www.bluejeanscable.com/articles/is-your-cat6-a-dog.htm
======
StillBored
First I haven't a clue why anyone would run cat 6, either do good 5E or
standard 6A. 6 is well not really useful..

All that said, the article does manage to skim over a few things it should
have talked about. There are actual physical differences between the cabling
specs which are a result of the 6A signalling requirements. The termination is
_MUCH_ stricter and likely the cause of 99% of the failures in cases where the
cables actually are 23AWG, properly twisted and isolated. Its these latter
three things which will allow you to identify "real" cat6A rather than the
stuff being relabeled by cable manufactures claiming to have found some secret
method of making what are basically cat5E cables 6A.

(back to my 5e comment. The thing to keep in mind about a lot of this is that
the standards specify minimums. The whole cat5E grouping was one where there
was a race to out-specify everyone else, which is why you can find cat 5E
500Mhz labeled cabling, although most places just renamed it to cat 6 and
charged a few cents more per foot. The other thing to keep in mind is that
these specifications end up being given in loss/crosstalk per foot, so its
quite possible to run higher data speeds on short cables that are non
compliant per foot, particularly if they are terminated properly. Hence other
comments I've made on this site about running 10GbaseT in my house on cat5E
without any apparent signally/packet loss due to the runs all being very
short.).

~~~
forbiddenlake
Why is 6 not useful and why is 5E/6A better?

~~~
ixf
6 is useful for non-dense high-bandwidth environments where you might need to
get 10G-BASET a little further than 5e will manage, but 6 doesn't address
enhanced alien crosstalk. This means in dense environments it may struggle. 6A
does, via shielding, and so will work better in dense environments (where
you're likely to see 10G-BT anyway).

~~~
mcv
Isn't shielding separate from the category? I recall seeing stuff like Cat5
FTP and Cat6 STP or some combination like that. I'm no cable expert, but from
what I understand, STP means shielded and FTP has some other kind of
shielding.

I think I put Cat6 STP or FTP in my home. Whichever it was, I wanted to have
the best cable I could possibly find, because I don't want to have to redo
this every 10 years.

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wrs
I've been buying Blue Jeans cables for a long time (starting with audio/video
cables, and more recently Cat6) because I love their no-b.s. attitude. And if
you're in Seattle and ask nicely they may even let you drive over and use
their fancy tester on your existing cables.

On the A/V side their story was basically "this is the same cable that the
studio that made the content you're watching is wired with, and you don't need
anything more than that".

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Mathnerd314
I guess the article isn't dated but judging from the Internet Archive it
should have a [2013] tag.
[http://web.archive.org/web/20130727071218/http://www.bluejea...](http://web.archive.org/web/20130727071218/http://www.bluejeanscable.com:80/articles/is-
your-cat6-a-dog.htm)

~~~
handedness
Thanks–updated.

------
Havoc
They kinda gloss over one point - the ones that passed/semi-passed are the
short ones.

For a 1m patch cable noise rejection, cross talk & similar length isn't really
an issue.

Like it or not manufacturers get away with it because in the vast majority of
situations a cat5 or even a failing cat5 has no real world consequence. It
fails the standard yet still works in practice - on a physical level. Plus the
network stack built on top of that has further fault tolerance.

If it's a long cable at the edge of tolerance or you're in a mission critical
datacenter then yeah maybe worry about this stuff. Everyone else just grab a
patch cable off amazon.

~~~
kiallmacinnes
The specs define the ratings in terms of length though, don't they?

That suggests to me the tester takes the cable length as an input, and gives a
valid rating for the length?

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BuildTheRobots
Cat-6, pah. Use barbed wire like a real sysop...

[https://news.ycombinator.com/item?id=15910263](https://news.ycombinator.com/item?id=15910263)

~~~
M2Ys4U
Or wet string:
[https://www.bbc.co.uk/news/technology-42338067](https://www.bbc.co.uk/news/technology-42338067)
/ [https://www.revk.uk/2017/12/its-official-adsl-works-over-
wet...](https://www.revk.uk/2017/12/its-official-adsl-works-over-wet-
string.html)

------
gok
I wonder if Cat 7 cables are similarly bad. I would have thought that since
you can visually verify that the pairs are all shielded, it would be harder to
fake it.

~~~
Dylan16807
Cat7 is in a weird spot. It's been rendered basically obsolete by 6a, which
has performance that's almost as good and allows for full-distance 10gig. And
while 7a was specified with the goal of supporting 40gig, it looks like 40gig
is going to require cat8.

And you're not really supposed to put RJ45 plugs on cat7/7a either.

So while you can verify the foil is in there, it doesn't say all that much
toward the total quality, since they're not quite a standard cable at all.

~~~
Abishek_Muthian
But isn't Cat7 better at shielding compared to Cat6a?

~~~
Dylan16807
It has stricter requirements for the most part. But whether you're better off
buying Cat7 with nonstandard plugs, vs. a model of Cat6a where they used
shielded wires? I'm not sure.

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tossandturn
On the other end of the spectrum (not testing specifications, but just simply
"does it network?"), I have successfully ran a 100BASE-TX connection between
industrial equipment using individual (not twisted) 24-AWG wires over 20ft.

~~~
ocdtrekkie
Seeing what people have done with legacy phone wire sometimes is just
disturbing.

~~~
cr0sh
When I was in high school, I helped my friend get cable TV back to his bedroom
by patching it over a really long length of phone cord. Crappy picture, but it
was better than nothing, and he didn't have to share the living room TV any
longer (his older brother later ran proper coax).

------
jabl
Semi-off-topic Q: Why did twisted pair cables become the standard for
ethernet? Seems to me from a signal integrity standpoint that coaxial (yes,
there was "thin" and "thick" ethernet back in the day) or twinax type cables
would be much better? Were they originally cheaper than coax, or what is the
reason?

~~~
avian
Cost and simplicity of installation. Twisted pairs and crimp-on RJ connectors
were already widespread in telecom due to POTS. If not for anything else, they
were cheap and their reliability well understood due to economies of scale.

On the other hand, coax cable was significantly more expensive per length.
Compared to RJ, BNC coax connectors were expensive and hard to correctly crimp
onto the cable. When computer industry tried to make them cheaper it also
resulted in very crappy products.

Unreliable connections were cause of most of the gripe with older coax-based
networks. Which is kind of counter intuitive. A properly made BNC is very
reliable and still used extensively in electronics test equipment and RF
applications. But apparently reliability just didn't scale down cost-wise.

~~~
flyinghamster
I also don't miss the daisy-chain wiring of coax Ethernet. Any one connector
getting out of whack, or a bad/missing terminator on either end, would take
the whole network down.

~~~
avian
Yes, but network topology is orthogonal to the type of cable used. We could
have just as well used coax for modern switched connections.

~~~
chrisdhoover
We did star configure CCTV systems using RG59 and RG6. The cables are heavy
and the connectors big. You can't get the same density as with UTP. A 48 port
coax switch took 4U versus a 1U UTP switch

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brink
I just bought 1k feet of Cat 6 cable and ran it through my house two days ago.
Would have been useful to know then.

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ramenmeal
Anyone willing to suggest a cable that meets cat 6?

~~~
softfalcon
I bought 2 of these at 75 feet for $16 CAD (each) and it's maintaining
expected 10 Gigabit on my home network.

[https://www.amazon.ca/gp/product/B00H41LYGM/](https://www.amazon.ca/gp/product/B00H41LYGM/)

~~~
Dreami
Does "maintaining 10 GBit" only confirm Cat6? I don't want to __* on your
recommendation, just want to be nit-picky about these things after such an
article :)

~~~
nomel
I used to work work for a company involved in 10GE some years ago.

I believe maintaining would be no link drops, but would include fast-retrains,
where the cable coefficients are quickly synced without losing link, resulting
in some number of dropped packets around the event. Low signal-to-noise will
result in a higher bit error rate and sporadically dropped packets.

Adding aggressors (noisy fluorescent tubes, power lines, RF transmitters, etc)
would eat away at the margin. But, if you're doing short runs (like 30m), then
you've got absolute loads of headroom, at least with the fairly standard
equipment we were testing. And also, the bit error rate is for full speed. If
you don't have constant 10G traffic, then your error rate will be
proportionally lower since there will be a bunch of "idle" time.

When testing these, there's a bit error rate test performed at different
lengths of cable. IEEE used to recommend something like 10^-13 (not sure if
this has changed), but we would test, with some margin, at the full 100m using
cables wrapped on spools (no external aggressors). We would also test with a
"5 around 1" configuration, with 5 other fully active cables tied around the
cable under test. If I recall correctly, this test required the full 10^-13.
All of these cables were periodically verified to meet all specs.

But regarding cable quality, we would buy thousands of meters of cable without
issues, _from good vendors_. You may have trouble finding compliant cable from
China. If there was a problem, it was usually from someone bending and putting
a permanent kink in the cable (causing a discontinuity in the impedance) or
closing a door on it.

------
llama052
I'd argue that if you're not doing a home setup, you should use fiber for
anything 10GBe+. Less latency and power draw.

~~~
meitham
Can Fibre support PoE? As that's really useful at home.

~~~
LeonM
I don't know if you are being sarcastic or not, but there are optical cables
that are bundled with copper conductors for power delivery.

~~~
meitham
Not sarcastic at all, I was genuinely wondering, and thank you for pointing
out the copper wire in optical cables, I didn't there was such a thing.

------
eyeareque
One thing to watch out for is CCA cat cabling. It’s cheaper, because it’s
copper coated aluminum. I have no clue if it reaches spec, but i don’t think
it’s worth it because it would cost so much to rewire your house again later
(or trace down an outage/packet loss in production).

~~~
kokx
I actually have CCA cabling. On purpose.

Why? It's cheaper. And I only had to run about ~15 meters through my small
rental apartment. And it basically cut my cabling cost in half while having
enough reserve cables left.

It hasn't failed on me so far. When I buy my own house, I will definitely
switch to better cables. But in such a small rental apartment, which I won't
be living in too long, I didn't find it worth my money to buy better cabling.

------
sinuhe69
For our projects, we always sourced directly from big names in the industry
like Nexans and LeGrand. With a hefty price, of course. But I always wondered
whether their cables are worth the price. Of course, we have let our system
integrators tested and reported diligently but yeah for big money, rigging is
not so far fetched!

------
otterpro
Is there any testing equipment that can test for compliance, and is
inexpensive? Fluke cable tester (DTX-1800) that was mentioned cost $40,000! I
saw an eBay listing for $6500 for used one. There are other cheap testers out
there but they seem to be just continuity tester, and doesn't test for cross-
talk, etc.

~~~
Already__Taken
The cheapest test equipment is going to be some spare computer hardware at
each end and a passing a test-suite of your expected performance numbers.

------
vinceguidry
I'm going to be changing out the flooring of my condo at some point and am
wondering if there's a decent solution for underfloor wiring that doesn't
involve building a raised subfloor. Or perhaps I could build a very small one,
I just wouldn't want to just wing it.

~~~
gog
I did just that few months ago. I had an electrician come and make channel in
the floor, lay in it some plastic tubing and later he pulled the cables
through it.

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amluto
I would love to see an Ethernet spec for >100m runs, perhaps at lower speeds.
If I could do 1 Gbps at 150m on Cat 6A cable without egregiously exceeding the
spec, it would be great.

~~~
Dylan16807
As long as you meet the signal integrity standards, I don't think you
_majorly_ violate anything. So run one speed level slower than your cable
normally supports and do some math on crosstalk per meter.

~~~
rocqua
Not sure whether this still holds for 1Gb and faster ethernet, but there used
to be a maximum length due to collision detection.

An ethernet frame has a minimal length, and since the cable (used to be) a
shared medium, frames could collide. Such a collision could be detected by
senders whilst sending the frame, allowing for a re-send. However, when the
cable is long enough, you could get collisions happen after you are finished
sending.

I'm guessing that the newer standards that only allow point to point
connections invalidate those requirements though.

~~~
Dylan16807
That's not actually true. When the 100 meter limit was established, a minimum-
length frame would be 10 kilometers long.

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CamperBob2
Seems like the actual issue is that the specs are way too tight. If 80% of the
cables fail the test but virtually all of them work fine in the real world,
what does that say about the test?

How common is it for someone to buy one of the retail-grade cables they're
discussing in this article, and find that it doesn't work reliably?

~~~
phinnaeus
More specifically, for a digital signal, what does "working, but not up to
spec" look like? Occasional packet loss? Corrupted data that is masked by ECC?

~~~
sigstoat
"working, but not up to spec" can mean "works today, stops working tomorrow
when subjected to a bit more nearby electrical noise". 10GbaseT links
frequently can't negotiate down, so your link can just stop working whenever.

