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Should Network Cables Be Replaced?
Jyms writes "As technology changes, so hubs routers and switches are upgraded, but does the cabling need replacing, and if so, how often? Coax gave way to CAT 5 and CAT 5e replaced that. If you are running a 100Mbit/s network on old CAT 5, can that affect performance? Do CAT 5(e) cables get old?"
CAT6 is a PITA to use residentially. It is much stiffer, due to a "coffee stirrer" embedded in the middle, and doesn't bend well at all. I just downgraded from CAT6 to CAT5e for hooking portables up to my GbE LAN, just because of how unwieldy CAT6 was.
The CAT6 plugs can also be a problem -- they are by necessity slightly thicker (the strands alternate in height when crimped), which can make them a tough fit for some devices.
Foresight certainly helps. I wired my home twelve years ago with 622 Mbit/s teflon-coated copper twisted-pair ATM wiring. It was the best I could easily (and cheaply since it was left over from a large commercial project) obtain. Except as noted below, since then, I've detect no material degradation in cable testing, and, needless to say, it handled the leaps from 10 Mbit/s (1997) to 100 Mbit/s (2002) to 1 Gbit/s (2009) with no difficulties.
According to a new (borrowed) cable tester, all the runs look capable of sustained 10 Gbit/s.
At current rate of progress in speed that should take me at least to 2021 before I start noticing that I'm no longer keeping up.
Of course with my luck, in my area, broadband will still probably be 10 Mbit/s and capped at 90 GB/month.
In my (admittedly limited) observations, you can have about four sources for run destruction:
1. Work hardening and breaking due to excessively sharp bending. (Be careful on insulation, and teflon coating = nice -- makes cable much harder to bend sharply)
2. Oxidation problems especially at the terminal. I've had terminal problems with wiring in an indoor pool area (vapour barrier separating it from rest of the home). Salt water + generated chlorine seem not to like metal in general. People unlucky enough to have installed the Chinese contaminated drywall might have similar problems.
3. Tension on cable (especially at terminal). Buildings shift, flex, settle, and twist. And not just in earthquakes. Competent installation helps here, especially if you have to redo a corroded terminal and need more run length.
4. Renovation. Whether it's a nail through the wall, a drill in the wrong place, mistakes can happen.
5. Animals. Squirrels getting into the attic managing to destroy infrastructure in a friend's house.
I've not had problems with (1), (3), (4), (5) but friends have. I would assume (5) is not a big danger in most office environments, but one never knows. As I say, my experience is primarily limited to my home and those of friends who've also wired up. And my sole problems have been at the termination point, not with cabling itself.
My advice is... buy good quality cabling -- better quality than you need. Don't get your installs done by cowboys, and try to think ahead.
Tough advice sometimes to follow when you don't control the budget.
-Holmwood
While you can link at those speeds with Cat5 you cannot actually get those speeds. Usually it tops out about 200-400mbit for me when I've tried. For most uses that's perfectly fine but in some cases it's not like my entire graphics and video editing departments. Servers are all connected with Cat6 if they use a lot of bandwidth.
I ran into this problem in Vegas as the place only had Cat5 connecting all the rooms to their closets so I had to use LACP trunking to get my bandwidth up.
5 and 5e are only rated for 100MHz per pair, so although you can get link speed aggregated at 1000bT, your max throughput due to crosstalk, signal reflection, and EMI is going to limit your switch to a speed closer to 300-400Mbit. Many switches will detect Cat-5 issues and downgrade your link connection automatically on problematic runs.
Connector quality has more to do with the connection quality than the cable itself. 5e simply has tighter specs to maintain. Really, there's not much of a difference, especially is you're using good patch panels.
Cat 6 runs 250MHz per pair, tru gigabit speeds are supported.
10G over copper is most commonly limited to 15M, and requires special 4 lane copper cabling, not Cat6 cabling. It's similar to Infiniband in design. A Cat 6 option was later offered, though few companies support this format. It's limited to 66m, and suffers similar bandwidth issues due to signal quality that running Gig-e over Cat-5 exhibits. Cat6a cabling can be used for 100m 10G deployments. Note this requires 650MHz Cat 6 cable ends, not 250MHz cat 6 cable ends as are normally deployed, for which there is a difference, and also requires 10G rated patch panels. Cat 6 cable can come in one of 3 thicknesses (guage). only one of these is commonly reccomended for 10G speeds.
Cables do go bad over time, due either to environmental factors or movement. Exposure to direct sunlight is bad fort cabling. Non-constant temperatures is also a cause of degredation.(cables in plenem space or inside walls tend not to remain at constant temperatures). Oxidation of the copper connector is the most common failure. higher quality cables and patch panels use silver, gold, or other corrosion resistant metals for this reason. Many cables are also made with lower quality plastics that simply fail over time (some are practically designed that way I sometimes feel). When the plastic fails, the cables corrode quickly.
More often I find a switch port fails before a cable (usually because someone plugged something in they should not have, or a charge makes it way into the cable due to being too close to a power cord, or long term exposue to magnetic fields causes elecrical resistance and damages the switch over time.
typically, I'd leave cables in place until a hardware upgrade or data bottleneck justifies the change. ALLWAYS use high quality cables rated for the installation location. lower guage (thicker copper) are generally better, but they should ALLWAYS be within spec. Buy cables from companies that offer 20 year lifetime warranty. (Hitachi, Mowhawk, etc) Have them installed by professionals who back that warranty and use properly rated panels and punch downs and you should have no issues. Anytime you;re running cables, allways run a class of cable 2-3 tiers better than your current needs, and for workstation drops or other complicated runs, allways run spares (the labor typically costs more than the cable, and running 2 or 3 at once costs less than 1 now and 1 later). Use cable trays or hooks EVERYWHERE, never let cables lie on ceiling tiles or underneath floors in channles.
This sounds like overkill, and probaly is for a small business, but when you have 14,000 desks in your copmpany (most with 2 netowrk and 2 phone drops) and over 3,500 servers, labor to replace cabling tallies in the millions of dollars...
There is no contest in life for which the unprepared have the advantage.
Although shielding is nice to have, it's not necessary for network cable because network cable is balanced twisted pair. Indeed, most high-performance network cables are not available with shielding, they can't maintain the spec with a shield in the jacket. It might be that your cable is older.
If you do have shielded cable, don't ground both ends!!! Bring all cables at one end to a common ground, and let the other end float. Otherwise, you will create a ground loop and actually make the noise worse.
Bruce Perens.
Grounding one end makes the shielding at the ungrounded end an efficient antenna, and can actually increase the radiation from the cables.
Cable shielding isn't a good way to avoid inteference with the signal on the cable, and isn't a good way to avoid radiation by the signal on the cable, unless properly terminated for one specific frequency (or narrow frequency range). One or both ends of the shielding would need to be coupled to case ground by a capacitor chosen for the frequency that you want to shield.
Shielded cable at this frequency is likely to cause more harm than good. There's usually little need to shield against common-mode interference, and I've never heard of shielded cable being used in a TEMPEST set-up (carefully matching impedances is the best way to avoid emissions, creating giant gorund loop antennas is not).
Socialism: a lie told by totalitarians and believed by fools.
He said FTP, which is also known as S/UTP, screened unshielded twisted pair, or "fully shielded" twisted pair.
The difference between FTP and STP is that in STP, each cable pair is shielded.
FTP has only an overall shield that covers all the pairs (each pair isn't individually shielded).
So FTP _is_ shielded UTP.
5 and 5e are only rated for 100MHz per pair, so although you can get link speed aggregated at 1000bT, your max throughput due to crosstalk, signal reflection, and EMI is going to limit your switch to a speed closer to 300-400Mbit. [...] Cat 6 runs 250MHz per pair, tru gigabit speeds are supported.
That is incorrect. Gigabit Ethernet (1000BASE-T) uses the same bandwidth as Fast Ethernet. The higher speed is achieved by using
1) all four pairs (Fast Ethernet uses two),
2) each pair in both directions (Fast Ethernet uses one pair to send, one to receive), and
3) a more efficient encoding (more bits per baud).
The full Gigabit Ethernet speed is specified for Cat5 cables.