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  #1  
Old 03-03-2008, 04:34 AM
marchen marchen is offline
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Hi Guys,

Recently some of our networks cables started to give problem and we have replaced few of them. We are not sure what is the root cause of this issue. Do you guys have any idea or experience about it?
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  #2  
Old 03-03-2008, 03:55 PM
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KenB KenB is offline
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I have heard rumors that high heat, such as in high-density racks, can de-rate cabling. Are your failing cables geting hot? If not, maybe you can say more about your situation.

Ken
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Old 11-30-2008, 12:19 AM
attagirl attagirl is offline
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Age would be the first factor I would look at. How they are stored would be another factor. Because if you are replacing cabling with outdated bad cable that would be a problem.
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Old 12-22-2008, 08:44 PM
Schumie Schumie is offline
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Another aspect to take into account could be that as the cables age, they become stiffer and more fragile.

This would then make them more susceptible to failure if someone is working near or on the cable itself.
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Old 12-25-2008, 03:01 AM
tom tom is offline
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Yes, we also have some of the cable problem. We have private network for our cluster boxes and some times heartbeat signal gets failed because of the cable problem.
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Old 12-29-2008, 08:18 PM
Neoeclectic Neoeclectic is offline
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The primary cause of communication degradation or failure is due to stress on the cable itself. The secondary causes are generally heat, interference, or insertion loss (which may not be the cable itself).

Proper cable management and handling is critical for any cable expecting to service an application or server on a long term basis. I've seen too many examples where people mishandle cables causing stress that eventually causes diminished communication performance.

The first thing regarding cable handling is understanding that the cable is not elastic and has its own stress limits. All cables should run or hang with a natural sweeping motion for all twists and turns. If you have to make a 90 degree turn don't bend the cable into a corner, but rather lay it down in a 90 degree arc. When routing cables through cable management ensure that there is a minimum of a 90 degree arc through all transitions where possible--or whats called a "natural sweep"--minimizing the stress to the cable.

Secondly, when storing cables the biggest mistake most handlers make is winding the cable up into a tight spool about the size of a teacup saucer; this is a no-no. Or they might wind the cable around their arm like an extension cord adding stress to the cable if done too tightly. This diminishes the quality of the cable and cables degrade faster at stress points. Also vigorously tugging on cables when pulling them is a no-no since the integrity of the cable is not congruent throughout. In other words, if you're tugging on a cable too hard there's a part of that cable that is not as strong as the rest of it and you're adding stress to that weak area.

Heat is an obvious factor if you don't have proper cooling for your cabling plant. There's really not too much to say here other than to try not to make cable runs too dense or to try to steer them clear of extreme heat sources or areas lacking proper ventilation.

Interference is a common issue as well which is generally explained as "crosstalk" or even high density interference from other electromagnetic sources. If your cable is run too closely to a power source emitting high volumes of EMF that will definitely impact communication performance. Even routing networking cabling with power cables (if not properly shield) can cause the cables to absorb the "line noise" from the power cables. The standard in the 90's was the network cabling had to be a minimum distance of 6" from power cables. I am not sure if that is still the standard to date, but it is a good practice overall.

Crosstalk, or "alien crosstalk" can occur amongst network cables themselves. Try not to pack cables too densley as this will cause a drop in performance. Alien crosstalk can give the illusion that the cable is bad because of a high number of data packet errors when in fact the cable is fine. Insertion loss is a huge problem as well. If you're not doing "home runs" or directly connecting server to switch from end-to-end then you want to limit the number of transition panels from point A to point B. Currently the TIA standard is no more than 4 transition points to get from point-to-point. Anything more than that and have huge risks of "attenuation loss". All of these which may make the cable look bad but in the cable is perfectly fine. It's the conditions in which it was installed is what diminishes the performance of the cable.

You should always have some kind of cable tester on hand. If you have about $15k to splurge get a Fluke DSP-4000 which is pretty much what all cable installers use (more or less an industry standard). If you can't get the high end model there are cheaper ones that can range as little as a few hundred dollar but won't give you as much information. This is a standard tool that should be in every data center and can tell you if the problem is truly your cable or if it's outside factors. It can save you an immense amount of time, labour, and money in the long run.
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Old 01-27-2009, 12:30 PM
princee18 princee18 is offline
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There should be proper cable management but still time is the factor which has to be taken into consideration and we are left with the only option to change the cables.
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  #8  
Old 01-31-2009, 04:32 PM
vlada vlada is offline
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Quote:
Originally Posted by marchen View Post
Hi Guys,

Recently some of our networks cables started to give problem and we have replaced few of them. We are not sure what is the root cause of this issue. Do you guys have any idea or experience about it?
I want to say that we had this kind of problems. It was our mistake not to pay much attention to the age of cables. But after the replacement we do not have problems absolutely.
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  #9  
Old 05-15-2009, 02:11 AM
andrew25 andrew25 is offline
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I guess this is a common problem which we all are experiencing. In my most likely guess it was because of the internal heating in the inner racks of the cable along with the short life time which leads to these cable problems. One of my friends datacenter encountered this problem frequently.
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  #10  
Old 07-13-2009, 08:54 PM
egihosting egihosting is offline
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How hot is hot?
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