Hot answers tagged

70

30 Mbit/s is the same speed, no matter if it runs over copper or fiber. However, there are important link parameters other than link speed/pure bandwidth, so there may be differences. First, latency on fiber can be better than on copper depending on the line encoding - fiber requires much less elaborate encoding (see below) than e.g. xDSL. However, lower ...


39

No, it will not slow down a connection, but you need to be aware of the maximum length of a copper connection which is 100 meters. This needs to include the length of your patching cable from the host to the data point and also patch frame to the switch. However, when using Cat 6 with a 10 Gbit/s interface, you can only use up to 55 meters and would need to ...


33

For all practical purposes, there will be no effect on the speed of your connection. There will be a very insignificant amount of delay due to long cables. This won't affect the maximum speed of your connection, but it would cause some latency. pjc50 points out that it's about a nanosecond for every foot of cable length, which is a good rule of thumb used ...


26

30Mb/s is 30Mb/s, but ISPs usually sell you “up to 30Mb/s” because the speed of DSL technologies is highly dependent on the distance between your equipment and theirs. With fibre, you are more likely to actually get 30Mb/s because the underlying medium is less sensitive to distance.


22

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, ...


22

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


21

The accurate answer is that they are not Ethernet cables. The cables themselves are not limited to transmitting Ethernet, nor is Ethernet restricted to using just UTP cables. In the first case, they are often used with many different types of signaling, including as examples voice and serial. In the second case, you can run Ethernet over coax, fiber, or ...


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 ...


19

You might consider pointing out to your "network engineering professional" that the propagation delay in copper is LESS that that of fiber (in most cases). The difference between the two is on the order of 0.1C. So in round numbers, that's 0.3 ns/m. If we imagine the distance between you and the provider is 10 km, that's an additional 3&...


18

Sort of, to a very tiny extent. The longer your cable, the higher latency you experience - gamers call this "ping" time. However, the effect is about one nanosecond per foot of cable, which is unlikely to be noticeable in most cases. Especially as a single ethernet cable is limited to 100m. This matters for high-frequency trading and occasionally for email....


17

It doesn't appear that any one has explicitly addressed the reliability of transmissions over fiber vs copper. It may be true that, for example, your router is throttled to 30 Mbps, but the transmission over copper may produce more errors than over fiber. This usually results in retransmissions (TCP will do this automatically), which will consume some ...


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 ...


16

When you need crossover cables is often explained, but why is seldom explained. It has to do with the copper (often referred to as Ethernet) wire itself. In copper wiring, there are four pairs of two wires (eight total wires). The pairs are numbered 1-4. The entire copper cable is full duplex, which means data can be sent and received at the same time. But ...


12

One of the jobs of a router is to connect networks that have physically different transmission media. Twisted-pair Ethernet is extremely common these days, but fiber (Ethernet, SONET/OC, and others) is used for most high-speed or long-distance runs, and different types of layer-2 and layer-1 networks have been used in the past and are still in use today, ...


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

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

The very first Ethernet standards were designed for using a single, shared coax wire. There's no benefit in making the connection asymmetric in any way. Additionally, network nodes are generally viewed as equal peers from the technology design perspective (in contrast to specific network design). There's simply no motive in making a general-purpose network ...


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 ...


11

Copper (ADSL or VDSL) specifies a maximum peak speed whereas fiber specifies a maximum average speed. My glass fibre (FTTH) connection is artificially limited to 50 Mbit/s average. At the start of a large download the peak speed is larger than that, and then I see it dropping until it hovers near the promised average. Without the limiter it could reach 200 ...


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

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 ...


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

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

Can a single optical fiber support full-duplex communication? Yes. There are "BX" standards, e.g. 100BASE-BX, which use different wavelengths for send and receive. The transmit wavelength on one end needs to be the receive wavelength on the other end. For example, Cisco has these transceivers: 1000BASE-BX10-D and 1000BASE-BX10-U SFP for Single-Fiber ...


9

Q: Why is ethernet symmetric (when compared to ADSL's asymmetry). A: This is best explained by looking the technical reason for ADSL's asymmetry. Quoting directly from wikipedia: There are both technical and marketing reasons why ADSL is in many places the most common type offered to home users. On the technical side, there is likely to be more ...


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 ...


9

Your cable is not a proper UTP network cable as defined by TIA/EIA 568. In fact, the pairs used by the 10Base-T (10 Mbps) and 100Base-TX (100 Mbps) ethernet are 1-2 and 3-6. The 1000Base-T (1 Gbps) standard requires all four pairs (wired as 1-2, 3-6, 4-5, 7-8). You must use a TIA/EIA wiring standard, either TIA/EIA T568A (normally used for home networking) ...


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

Nowodays, many ethernet interfaces are 'auto MDI/MDIX'. They detect the type of device connected and if needed reverse internally Transmit and Receive. This allow connection of 2 devices of the same layer with straight-through cable. APIPA is specifically made to provide IP addresses and allow IP communication in a network where there's no DHCP server. ...


8

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 ...


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