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41

No, the numbers are right (Page 46). If I can reword your question, it's "Why should I use fiber if the propagation delay is worse than copper?" You are assuming that propagation delay is an important characteristic. In fact (as you'll see a few pages later), it rarely is. Fiber has three characteristics that make it superior to copper in many (...


27

Some devices could only run at 10 megabit/s, so the device at the other end would autosense the speed to match. If a device that has a maximum speed of 10 Mbit/s is connected to a 10 Mbit/s / 100 Mbit/s switch, the switch needs to lower its speed on that particular port in order to effectively (efficiently) communicate with the device. These ...


23

Contrary to popular belief, there are cable color standards defined, just hardly anyone (myself included) follow them closely or at all. Check local jurisdictions for variants. ANSI/TIA/EIA-606-A Administration Standard for the Telecommunications Infrastructure of Commercial Buildings or the updated ANSI/TIA/EIA-606-B documents these standards. Generally, ...


23

It is used to split the outer shielding away without needing to use a sharp object which could potentially damage the wires themselves. It is commonly called a ripcord. Image taken from http://netx.us.com/Product%20pdf/Copper_Solutions/A6.pdf


19

This can introduce a number of problems, like additional attenuation or cross talk. Splicing is to be avoided whenever possible, but I have seen this work in a pinch although I would never recommend it. They key is to use a cable certification tester (not just a continuity tester) to make sure it still passes your required standard (Cat5/5E/6) after ...


16

When you use TIA/EIA-568B on both sides this is a straight through cable. The colors of the inner jackets don't really matter, much the same as it makes no difference to the operation of the network if you use a network cable with a black or yellow outer jacket. However, the standard is in place for a real reason, and that is that the cabling system should ...


14

Remember 10Mbps came first, then 100Mbps, then 1000Mbps. The advantage of supporting multiple speeds and automatically switching between them is you can upgrade your network gradually without having to worry about what speed each device supports or replacing everything at once. You just plug a device in and it connects at the highest mutually supported ...


13

Per the ANSI/TIA/EIA 568, Commercial Building Telecommunication Standard, UTP cabling is limited to 100 meters. That length assumes up to 90 meters of solid-core (better performance, but fragile) horizontal cable, and no more than 10 meters of stranded (poor performance, but less fragile) patch cord divided between both ends. Installation is critical, and ...


12

A E said: OK @MikePennington, so what's the "right way"? Either hire a professional cable installer to check out your cable installation, or get something similar to a Fluke CableIQ. These meters perform detailed tests on the cable that reveal what you're dealing with. GigE has Signal to Noise requirements that simple continuity testers will not check. ...


12

Hi and welcome to Network Engineering. As for "delay" vs "latency": The terms are not always used consistently. Some hints may be found here. I think generally, the term latency is used when looking at end-to-end times for one direction, which essentially are composed of the sum of all propagation, serialization, buffering (and possibly processing) delays ...


11

Reasons to use shielded cabling You asked about using shielded cabling to protect ethernet from interference from heavy power currents. We mentioned above that shielded cabling isn't required in this case, but there are a few valid use cases for it: If you run cabling where there truly is a high potential for interference, such as ethernet cabling that ...


11

You'll find discussion of this elsewhere - see 'Why would I choose Copper over SFP+ for 10GbE?' - but broadly speaking SFP+ DA is, ignoring distance: Cheaper at the adapter side. Lower power and latency. Gives added flexibility if you need to move to fibre later. 10GBase-T on the other hand is: Cheaper at the connector side - patch leads being cheaper ...


11

As I currently do not have the full standards available to me, the best answer I have seen on this topic is from the forums at the BICSI website. Based on this post by an employee of Fluke Networks (manufacturer of a number of popular cabling test units), there appears to be no minimum length in the standard. However, there are both an implied minimum ...


11

Anything you choose to do will increase attenuation and potentially shorten the distance you can run PoE. There is no best practice answer to this as the best practice is to re-run the cable. Since you can't (or aren't willing to do this) then I would do one of two things, although I would still highly recommend running a new cable (you can use the old ...


10

There is no minimum cable length when talking about standard copper-cables. When it comes to fiber, there is a minimum length depending on technology, diodes and so on.


10

Common practice would be just to cross everywhere since you will always get an uneven number of crosses which will result in an overall cross. But this only works if your fibres were installed by a sane company. Basically you need to know that: a) Couplings cross b) You need crossed cables/trunks everywhere (which *should* be default) So let's test that: ...


10

Cross on one of your patch cables. You want your installed fiber plant to be labeled correctly at both ends (Strand 1 at Site A = Strand 1 at Site B).


10

The colors are just there as an ease-of-use tool. What really matters from a functional standpoint is what cable is connected in the jack in what position. Electrically the colors of the wires make no difference. It will require care, but you can identify the wires per pair by "ringing" them out with a multi-meter with a continutiy check ( the symbol ...


9

This is directly addressed by the ANSI/TIA/EIA 568-B Commercial Building Telecommunications Cabling Standard: Connecting Hardware and Polarity Optical fiber shall be installed with odd numbered fibers having Position A at one end and Position B at the other. Even numbered fibers will have position A and B reversed from the odd numbered fibers. ...


9

I once made a crossover adaptor using a coupler and 2 tips butted almost against one another with probably less than an inch of cable between each connector point. Worked great! Point is, you won't find any standard spec on a short cable length. All you have to go off of here is user experience. There are tons of threads where people say their 6" patches ...


9

I know this is an older question, hopefully you've solved it by now, but I wanted to toss in my two cents, for the benefit of future generations if nothing else. First of all, yes, ethernet and PoE specs mean you can do exactly what you're trying to do, and run two PoE cameras over a single Cat5e. First up, there are very, very, VERY few IP surveillance ...


9

Its called a ripcord and is used to cut thru the outer casing of the wire so you don't have to use a knife. To those who say it is not strong enough your not using it right. Grab it with a pair of needle nose pliers wrap it around the tip a couple times and then pull back it works perfectly. I have used it as a ripcord for more than 30 years. Granted on ...


8

But why in both standards there is one pair that is not adjacent (pin 3 always pairs with pin 6)? This goes back to compatibility in phone system wiring. It is based on the TIA/EIA 568 standard. The middle pair (4,5) was used for the first voice circuit. the next pair (going out from the middle - 3,6) was for the 2nd phone line. The reason it makes sense ...


8

Yes, a bridge / switch adds some delay to a frame - in the order of 1 to 20 µs. For switches you usually speak of latency - the delay between receiving a frame and forwarding it out another port. A switch requires some time to receive the destination address and make the forwarding decision. Store-and-forward switches (the common kind) need to receive the ...


7

The colors for RJ45 cables are not specified. You can get any color you want. In the DC we color-code length: 0,5m yellow 1,0m white 2,0m blue ... Everything >20m white again In the office we use black cables for all equipment as it doesn't stick out. (Bright orange/red in a snazzy conference room doesn't look too good IMHO.) For optical cables most of ...


7

As far as I know there is no standard for colors in twisted pair ethernet pigtails. As Mike already explained, color codes are local to the facility and different facilities could use different color codes. Regarding optical fiber pigtails, there is a standard color code for them. SMF pigtails are yellow and MMF are blue or orange depending on its core ...


7

If you have a fiber scope (you really should, to check if connections are clean) the core size (but not OM level) is obvious by inspection, especially if you look at a known connector and then the unknown connector (or better yet, two known connectors, one of each size.) Image from theFOA.org


7

As per IEEE 802.3 Clause 38, 1000BASE-SX requires OM2 (500 MHz·km for 850 nm) for max. 550 m reach. As a superset, OM4 is fine as well (there's little point buying OM2). With 10GBASE-SR the reach over OM4 is reduced to 400 m, so you're also good for an upgrade later on. There's also OM5 but it's only for higher speed WDM, not for longer reach with 850 nm. ...


7

Simply put, twinaxial cables allow only very short distances, under 10 meters. And they are used in networking, for example both 40Gb and 100Gb standards support twinaxial cables... ...up to 7 meters. Due to this limitation they are mostly use in Direct Attach cables. (outside of networking, they are used in USB3 or Display Port cables for example).


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