Why Your Cat6/5e Network Cable is Slowing You Down: An Interview with Blue Jeans Cable

K

KurtBJC

Audioholic
It's especially silly because Ethernet is full duplex; there's information flowing in both directions at the same time on two separate sets of conductors.
Not only that, but all the lines in an Ethernet cable are balanced, too--so even without duplexing, the current is flowing one way in one conductor while flowing the opposite way on the other conductor of the same pair. And, of course, current doesn't "know" which way the information is going, even if information were flowing only in one direction.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Not only that, but all the lines in an Ethernet cable are balanced, too--so even without duplexing, the current is flowing one way in one conductor while flowing the opposite way on the other conductor of the same pair. And, of course, current doesn't "know" which way the information is going, even if information were flowing only in one direction.
Good point. BTW, I've been a customer of yours for years, Kurt. Keep up the great work.
 
D

dingus48

Enthusiast
Excellent, informative and objective article that is BS-free and conforms to common sense and scientific methods. More like this.

If what I want is offered by Blue Jeans, they get my business going forward (never really knew much about them until now).
 
psbfan9

psbfan9

Audioholic Samurai
I want to say that I have been very happy with my cables from Blue Jeans. Even more important, I've been extremely happy with the customer service provided by Blue Jeans.

Kurt, when you measure these cables, do you compare the twists in the colored cables? If all the wires are twisted the same would that cause interference and lead to poor test results? If so, would changing the twists result in better test results?
 
S

scott911

Full Audioholic
I trust blue jeans. When I saw their name in this article heading, I knew this was something I should read.

A while back, I was having heartache caused by a 30 foot hdmi run; they were helpful, solving my dilemma with good value, great service, and exceptional quality product.
 
K

KurtBJC

Audioholic
Kurt, when you measure these cables, do you compare the twists in the colored cables? If all the wires are twisted the same would that cause interference and lead to poor test results? If so, would changing the twists result in better test results?
We don't compare the twists when measuring them, but when the cable was manufactured, the twist rates were set relative to one another to minimize crosstalk. And yes, you're right about the twist-rate issue; here's how it works, more or less.

Common-mode noise rejection in a twisted pair cable works if we assume that the source of the interfering noise hits the cable symmetrically--that is, if there's +10 microvolts on the "plus" member of the pair, there's likewise +10 microvolts on the "minus" member. If the receiving circuit is properly balanced, the differential amplifier on the receiving end will not "see" either of these because they arrive in time with, and at the same amplitude as, one another.

For external noise sources--e.g., a noisy doorbell buzzer located a foot away from the cable--this assumption of symmetry works well. The problem, when you get to crosstalk, is that there is a pattern to the signals in the other pairs. If, worst-case scenario, the twist rates in all of the pairs are identical, the noise is extremely asymmetrical, because the same wires will repeatedly approach, and separate from, one another again and again along the length of the cable. So, if the "plus" conductor of pair 1 is repeatedly close to the "plus" conductor of pair 2, and is repeatedly (relatively, of course) far from the "minus" conductor of pair 2, this will mean that the noise which comes from the "plus" conductor of pair 1 is highly asymmetrical in pair 2. At the same time, the corresponding profile of the "minus" conductor of pair 1 relative to pair 2 will be equally asymmetrical, and in opposite direction. Now that we've completely invalidated the "symmetrical noise" principle for this hypothetical cable, common mode noise rejection works very, very poorly and crosstalk is really high.

If you've got four pairs in a bundle, too, you have to worry about six different crosstalk relationships--so you can't just arrange the twists so that pairs 1 and 2 have minimized crosstalk. You've got to find four different twist rates that make the relationship between the pairs such that the crosstalk from each pair hits each other pair in a relatively symmetrical fashion, so that common mode noise rejection can do its work.

My suspicion is that if one were to look at some of the "Cat 6" cables we tested, you'd find that the twist rates are not well-chosen, and that this is why some of them are really lousy on crosstalk.

To sum up: you're very right that the twist rates matter; you're right that having the same twist rates would strongly affect the test rates; and yes, if that were the case, changing the twist rates would improve things. Finding the optimal twist rates, by the way, turns out to be a fantastically difficult mathematics exercise--once upon a time, Belden actually rented a Cray supercomputer to solve that problem. Of course, these days computing power isn't quite so difficult to find as it was back then.

Another problem, incidentally, on crosstalk is that common-mode noise rejection in a cable gets tougher as frequencies go higher, simply because no pair is ever completely free from intrapair (not to be confused with interpair) skew--that is, the electrical length of the two conductors isn't identical. This means that even when noise IS completely symmetrical relative to the cable, it may not cancel as well as one expects because it arrives sooner on one conductor, and finishes later on the other. When we're dealing with analog mike cable, this is not an issue because we're talking about picoseconds here--but in high-speed data, picoseconds matter.

Kurt
 
T

tvrgeek

Enthusiast
Darn Kurt, correct again. Guess I need to order a 1000' of Belden. I have observed some packet loss in my network pulled with orange box store bulk cable. One length of "6e" did not have a core, so that is a hint. I went to shorten another pre-made 100-footer, and the pairs were not bonded. I never new there was no verification of the standards.

Any hint on consistently reliable RJ45's vendors? I thought they were the same but alas, the ones in my $6-a-hundred made in China pack are a pain to get lined up.

Any issues with counterfeit bulk cable? If it says Belden, is it likely to be?

I have used BlueJeans for all my difficult issues, long S-video, long HDMI and they have worked perfectly pushing past the nominal specification of what I should be using. They are the go-to I always recommend.
 
K

KurtBJC

Audioholic
One length of "6e" did not have a core, so that is a hint. I went to shorten another pre-made 100-footer, and the pairs were not bonded. I never new there was no verification of the standards.
The lack of a spline on something labeled Cat 6 is pretty strongly suggestive that something's wrong. There's no spec requirement for a spline as such, but most people have found one necessary to meet spec because it controls pair-to-pair spacing much better than a non-splined cable, and pair spacing is very important to crosstalk. The lack of bonding is not surprising, because right now Belden is the only company making bonded pairs--again, something not called for by spec, but it helps to control dimensions which helps to meet spec requirements.

The fact that there's no verification agency for the standards does surprise a lot of people. In fact, on one message thread on another board there are a few people who insist very simply that we must be wrong because it wouldn't say "Cat 6" on the cable if it wasn't Cat 6...sadly, not so. The market is really driven hard by bottom-price resellers who often sell tons of cable but know almost nothing about the electrical attributes of what they sell.

Any hint on consistently reliable RJ45's vendors? I thought they were the same but alas, the ones in my $6-a-hundred made in China pack are a pain to get lined up.
We've been using some from Sentinel (made in York, PA) which we really like; I think they're available in retail-pack sizes from some vendors--we buy 'em by the box of a thousand, which is a bit much for a normal home project. Bel Stewart also makes good ones, also US-made. But for something that's more widely available and of high quality, probably the easiest one to find is Panduit--their Cat 5e plugs are just great, and their Cat 6 are very high quality but some people find them a bit fiddly to assemble. In general, if you're having trouble getting conductors to stay lined up, connectors that use a load bar (like the Panduit Cat 6, or most of the Sentinel or Bel Stewart ones) are easier to use.

Any issues with counterfeit bulk cable? If it says Belden, is it likely to be?
I haven't heard of counterfeit Belden turning up for some time, though it has been known to happen. If you're buying through a vendor who is a Belden distributor or OEM, you shouldn't have anything to worry about (in fact, we've got some Belden horizontal cable which we'd intended to make patchcords with, till we figured out there were better ways about it--drop us a note if you need some--it's all 23 AWG pairs and rather difficult to make patch cords with, but fine for between-jack installed wiring).

On "counterfeit" more broadly, there have been some cases of counterfeit UL codes on cable, involving Chinese goods; that this sort of thing happens is just one more indication that the companies which import a lot of cheap assemblies really have very little oversight of their vendors and very little idea what's in the package other than that this factory's bid was just a bit lower than another factory's bid. As to whether it's really Cat 6, or even 5e, or not, they just trust the factory and that's not a safe strategy.
 
K

KurtBJC

Audioholic
By the way, if anyone who's been watching this thread has been waiting for us to get Cat 6a cables back in stock, we've done that, effective today. We had a bit of a technical issue in production which is now resolved, with the result that our Cat 6a cables are passing by larger margins than before.

Kurt
Blue Jeans Cable
 
Markwinstanley

Markwinstanley

Audiophyte
I hope all matter resolved but here i wanna also tell that many of us will not have cable connection testers and it's possible to test a new cable connection using the netstat demand with House windows or OSX.

Initiate several big uploads along with data, or document replicates, to check out data with decreased packets along with retransmissions. In the event that presently there may not be any falls the actual cable connection is actually as effective as that must be. One of my friend also discussed with telesystemscorp for structured cabling and many issue related with wiring and many telecommunication.
 
W

webdawg

Audiophyte
I know this is an old thread but it is a very interesting article, and I still do not see much on the net about this issue.

That interview was full of knowledge, but does anyone know where someone can find some objective tests of purchased cables?

It is nice to read that they tested cables and their conclusions, but where are the actual results?

Why hide them? I cannot find any place to find some results on cables tested with expensive tester(s)?

Anyone have any results on short patch cables from monoprice?
 
jinjuku

jinjuku

Moderator
I know this is an old thread but it is a very interesting article, and I still do not see much on the net about this issue.
I don't believe there is much more to say on the net about this issue. It's cut and dry.

That interview was full of knowledge, but does anyone know where someone can find some objective tests of purchased cables?

It is nice to read that they tested cables and their conclusions, but where are the actual results?

Why hide them? I cannot find any place to find some results on cables tested with expensive tester(s)?
Kurt may be able to provide that. You could email them or call and ask.

Anyone have any results on short patch cables from monoprice?
I know for a while BJC would test a cable if you sent it in. Don't know if there is a charge for that or not however.

Interesting that Kurt will send the validation results with his cables but you can't get the same with AQ / Chord etc....

Maybe AQ can't do it because their Ethernet cables are 'directional'.
 
W

webdawg

Audiophyte
Thanks for the response. Me just coming up upon this type of issue leaves me wanting tables of results.

I agree that the issue is cut and dry, but what still is not, about a year later, is any results on specific cables, or published data/studies. Unless I am wrong?


It seems like this article brought the issue up, but no one has has taken the time to create/publish public results.

I will contact BJC.
 
J

jeff l.

Audiophyte
what can you say about the performance of cat5e cables using CCA instead of 100% copper? thanks.
 
Speedskater

Speedskater

Audioholic General
Copper Clad Aluminum cables.
At cat5e speeds it's won't matter.
As a 4 channel balanced audio interconnect it might.
As a speaker cable it will.
 
highfigh

highfigh

Seriously, I have no life.
While most of us don't have cable testers, you can effectively test a cable with the netstat command on Windows or OSX. Initiate some large uploads and downloads, or file copies, and look for statistics on dropped packets and retransmissions. If there aren't any drops the cable is as good as it needs to be. If there are drops or retransmissions it could be an end-to-end issue, and not on the cable, but if you use a local device, such as a NAS or another computer on the same switch, netstat probably suffices. If there aren't any drops or retransmissions you aren't slowing down the network connection. Be sure to also verify that the link speed is what you think it is; Ethernet auto-negotiates, so most devices will attempt to connect at the highest speed (usually 1Gbps), but if there are errors at that speed you might find your link auto-negotiated down to 100Mbps, or even 10Mbps. I've only seen auto-negotiation downward once, and that was several years ago, but I still look to be sure.
If you use the netstat command, what are you looking for- 'established', or does it show frequency/bitrate info? I would enter cmd in the search box and inter 'netstat' (no apostrophes) and click enter, right?
 
highfigh

highfigh

Seriously, I have no life.
Holy Cow AudioQuest went there:

DIRECTIONALITY: All audio cables are directional. The correct direction is determined by listening to every batch of metal conductors used in every AudioQuest audio cable. Arrows are clearly marked on the connectors to ensure superior sound quality. For best results have the arrow pointing in the direction of the flow of music. For example, NAS to Router, Router to Network Player.

Ok I really can't stop laughing.
When I read that kind of BS, I weep for humanity.
 
highfigh

highfigh

Seriously, I have no life.
Speaking of bulk cables.
Belden's CAT6 1000FT 550MHz cable rolls on ebay now for 100 + shipping. Why get anything of lesser quality ?
Belden Media Twist CMR CAT6 Cable 1872A 23 AWG Bare Copper Riser 1000 FT | eBay

Kurt, I understand the issue with potential legislation, but I am dying of curiously what brand cables are the 7ft cat 6 and cat 6e cables which both failed cat5e tests?
Could give us a hint please?
Where does that item show that the cable is Belden? I didn't see that name anywhere in the link.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
If you use the netstat command, what are you looking for- 'established', or does it show frequency/bitrate info? I would enter cmd in the search box and inter 'netstat' (no apostrophes) and click enter, right?
Ah, Windows. Try entering: net stats workstation

to the command prompt. I forgot; I've been using OSX too long.
 
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