Cat6 patch lead in cat3 style

Dieselboy · May 14, 2020, 12:26:32 AM

What do you guys think of this? My boss renovated his house and somehow found a supplier of these very thin, very lightweight CAT6 cables. I've been meaning to post this here for almost 12 months. $7AUD for 0.5m though.

Otanx · May 14, 2020, 10:15:12 AM

Short runs on those are good. Also don't run POE over it. Other than that they really help high density patch panels.

-Otanx

deanwebb · May 14, 2020, 11:52:15 AM

Quote from: Otanx on May 14, 2020, 10:15:12 AM
Also don't run POE over it.

Dooooooooooooooooo tell!

Otanx · May 14, 2020, 12:01:19 PM

Smaller cable, more resistance, more heat. You probably will be fine, but I don't want to be the guy everyone is looking at after the fire burns the place to the ground.

-Otanx

deanwebb · May 14, 2020, 12:33:32 PM

Quote from: Otanx on May 14, 2020, 12:01:19 PM
Smaller cable, more resistance, more heat. You probably will be fine, but I don't want to be the guy everyone is looking at after the fire burns the place to the ground.

-Otanx

Thanks, I was needing a little laugh today. I'm thinking of the guys I worked with that would bring this down on their heads.

Dieselboy · May 18, 2020, 08:56:20 PM

Yes that makes sense I suppose but I thought that the cat6 standard would provide assurances to the spec...

He's running all his PoE cameras on it. Will update you if anything occurs. They're just PoE cameras though so would be low (I think 6-ish) wattage. And these are patch leads only so limited to the server rack room.

Otanx · May 19, 2020, 08:41:27 AM

Some of this may be out of date, adn I am going mostly off memory from over a year ago when I had to dig into this so take it with a grain of salt.

Typically those thin cables don't actually meet the specifications for CAT6. I can't find a good reference because you have to pay for the actual standard, but there is a cable size it is supposed to meet for the strands. These thinner cables don't meet the minimum. It works because very few runs are a full 100 meters of cable. If I have a higher impedance because of thin wires then my system sees the 10 meter cable as if it is 15 meters, and I am just fine. Trying to run a 90M run of thin stuff might cause issues. By the time it got to the end the signal strength may not be high enough to read. In the real world even at 100M you will be fine because everyone engineers their gear to be better than the standard.

Also the CAT6 standard does not define anything about carrying POE. That falls under the IEEE POE standards(again you have to buy the standard), and if I recall correctly they just call out that the cable meets specifications from EIA/TIA. Putting more power down the wire with higher impedance will heat the cable up more than it was designed for. From Wikipedia the standard says you are supposed to de-rate the temperature rating for the cable to account for the heat being generated if you are doing more than 15.4W. So even if you are using the right sized cables you are supposed to take heat into account. Smaller cables will generate more heat. So in theory you could probably do all the math for thinner cables, and determine if you are OK. I suck at math so I would leave that to my brother.

For short runs there isn't going to be a problem. Long runs might cause connectivity issues. Large bundles of cables with POE may cause heat issues. Or they might not. When we did our large install for our building we specifically called out that the thin cables were not allowed so we didn't have to deal with it.

-Otanx

Dieselboy · May 20, 2020, 07:36:16 AM

Interesting! Thank you for the information Otanx

Otanx · May 20, 2020, 08:51:36 AM

No problem. When we built out new offices we looked at using them. Some of our closets are pretty high density, and the reduced bulk of cables would have been nice. We decided against it because of the issues above, and the fact that we should not have to touch the cabling after it was installed very often.

-Otanx

wintermute000 · May 21, 2020, 07:16:08 AM

I like them but I've only ever used them for short patches. Thanks for the info Otanx

config t · May 25, 2020, 11:49:56 PM

Good info Otanx.

This got me thinking about the direct attach copper SFP to SFP cables. They are pretty cheap compared to buying single SFPs and fiber but I haven't had to look into what the downsides could be.

https://www.bhphotovideo.com/c/product/1426615-REG/ubiquiti_networks_udc_3_unifi_direct_attach_copper.html?gclid=CjwKCAjw2a32BRBXEiwAUcugiLckOsb4oDVYveJA61zNI87nRM0rr_v_EMhIue2NUHmSvBNe87bzjhoCJMUQAvD_BwE

wintermute000 · May 26, 2020, 07:37:09 AM

nah they're fine, the downside is size and thickness. Ever tried to do a spine leaf with those? Out of control

Otanx · May 26, 2020, 08:52:59 AM

They work pretty well. Downsides are like wintermute said. size and thickness. Filling a 42U rack with dual homed servers the cable becomes unwieldy. They are also limited to 10M so doing rack to rack may not work depending on how long of a cable you need. There is also AOC, active optical cable (I think), which is the same thing as DAC, but uses fiber. AOC is thinner, and gets you out to 100M, but I don't see the benefit over using separate fiber and SFPs. I like sticking to fiber with LC. When I go from 1G to 10G I use the same cable. Then when I go from 10G to 40G I use the same cable using Bidi. Then go to 100G, and above. Never having to change the cable. Assuming you use single mode of course, but even multimode is doable if you use OM4.

-Otanx