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Author Topic: Ethernet cables: UTP vs. STP  (Read 1628 times)

phitsc

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Ethernet cables: UTP vs. STP
« on: April 27, 2015, 02:28:40 PM »
After buying a new central switch for my home network I noticed that a smaller gigabit switch in one of our rooms connected with only 100 Mbps. Because I had a similar problem recently where my laptop (which we now used for like 10 years!) connected with 1 Gbps to the central switch without problems, our brand new laptop did so only with 100 Mbps. While re-crimping the respective ethernet outlet fixed that problem, doing the same with the other ethernet outlet did not have the desired effect. As it turned out, the problem was the cable connecting the outlet with the switch! It was an UTP (unshielded twister pair) cable. After replacing it with an STP (shielded twister pair) cable, the switch connected with 1 Gbps.

I was also testing my internet speed recently and was very annoyed that I only ever got like a maximum of 100 Mbps down instead of the 125 Mbps which I pay my service provider for (not that I would notice the difference if I wouldn't measure it ;) ). I complained to the service provider and was informed that my modem was working flawlessly and that my signal was optimal. I was instructed to take measurements directly at the modem, which I did and voilĂ : 125 Mbps. Because of personal paranoia I have another router sitting in between my service providers modem (it's actually a router itself) and my home network. My service providers modem was connected to my router with an UTP cable!

Interestingly, I did not find any reference on the internet stating that UTP cables would only work up to 100 Mbps.

Ath

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Re: Ethernet cables: UTP vs. STP
« Reply #1 on: April 27, 2015, 02:43:15 PM »
It's to do with the Category of the cable.
CAT 5 is qualified for 100 MBit/s
CAT 5e for 1 GBit/s
CAT 6 for up to 10 GBit/s and requires better signal to noise ratios (10 GBit/s not over the full 100 meters)
CAT 7 for up to 40 GBit/s with even better signal to noise ratios and less crosstalk, using shielded pairs within the cable

More info here: http://www.xmultiple...xwebsite-forum24.htm
And Wikipedia on CAT 5/5e: http://en.wikipedia....iki/Category_5_cable

Stoic Joker

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Re: Ethernet cables: UTP vs. STP
« Reply #2 on: April 27, 2015, 02:46:24 PM »
Interestingly, I did not find any reference on the internet stating that UTP cables would only work up to 100 Mbps.

Nor will you, STP (Shielded Twisted Pair) is just normal Ethernet cable with an extra layer of RF shielding for high (RF)noise environments. It has nothing to do with the speed of the media, outside of ensuring it isn't hampered by external environmental conditions.

phitsc

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Re: Ethernet cables: UTP vs. STP
« Reply #3 on: April 27, 2015, 03:04:10 PM »
It's to do with the Category of the cable.
CAT 5 is qualified for 100 MBit/s
CAT 5e for 1 GBit/s
CAT 6 for up to 10 GBit/s and requires better signal to noise ratios (10 GBit/s not over the full 100 meters)
CAT 7 for up to 40 GBit/s with even better signal to noise ratios and less crosstalk, using shielded pairs within the cable

More info here: http://www.xmultiple...xwebsite-forum24.htm
And Wikipedia on CAT 5/5e: http://en.wikipedia....iki/Category_5_cable

One of the two cables has Cat 5E printed on it.

Ok, just checked the other one. It was indeed only a CAT 5 cable. When I wired our house I made sure to put in only CAT 6 to make it future proof. I should have been more careful with the patch cables as it turns out :-[.
« Last Edit: April 27, 2015, 03:52:01 PM by phitsc »

phitsc

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Re: Ethernet cables: UTP vs. STP
« Reply #4 on: April 27, 2015, 03:53:00 PM »
Anyway, thanks guys for pointing out that my problem was not actually UTP vs. STP, but CAT 5 vs. CAT 6.

SeraphimLabs

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Re: Ethernet cables: UTP vs. STP
« Reply #5 on: April 27, 2015, 04:41:49 PM »
I personally hate STP. The shield is annoying to work with when preparing the cable, and is of no benefit at all unless connected to a good earth ground at one end only. UTP cable is cheaper and easier to install.

Most installations don't take enough care in preparing the cable and properly grounding it to actually achieve any benefit from having it shielded, and accidentally grounding the cable at both ends can make the interference worse by way of ground loop.

Gigabit ethernet will work over even Cat3 at short distances despite being out of spec, but the further you go the higher quality cable you need for reliable transmission. These days I usually use Cat6 for all new installs, even though I have 5e cables over 100 feet long still in service and achieving reliable 1Gbps speeds.

The quality of the switchgear and NIC matters as much as the cable itself does. Cheap NICs and switches do a poor job of filtering noise and will be unstable at speed over a long or old cable, while the good ones can meet and even exceed the standards for network performance and noise immunity.

« Last Edit: April 27, 2015, 04:49:19 PM by SeraphimLabs »

phitsc

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Re: Ethernet cables: UTP vs. STP
« Reply #6 on: April 28, 2015, 01:14:46 AM »
I personally hate STP. The shield is annoying to work with when preparing the cable, and is of no benefit at all unless connected to a good earth ground at one end only. UTP cable is cheaper and easier to install.

Most installations don't take enough care in preparing the cable and properly grounding it to actually achieve any benefit from having it shielded, and accidentally grounding the cable at both ends can make the interference worse by way of ground loop.
Interesting. I certainly did not care when I made my home installation.


The quality of the switchgear and NIC matters as much as the cable itself does. Cheap NICs and switches do a poor job of filtering noise and will be unstable at speed over a long or old cable, while the good ones can meet and even exceed the standards for network performance and noise immunity.
That matches my experience with my old laptop, which had a reliable 1Gbps connection every time. It was actually quite a disappointment when I connected my new laptop for the first time and it connected with only 100Mbps. On the other hand it forced me to finally fix that problem (which I had known about for a long time already).