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69

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 ...


43

They include this because not all ports are able to run at multiple speeds or certain speeds. Running at only one speed was probably most common when 100BASE-TX first came out and a number of switches had fixed 100BASE-TX ports as uplink ports with 10BASE-T ports for providing access. However, it is common for many GBIC/SFP based ports to only run at a ...


42

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 ...


34

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

Good question. To answer it fully would involve a pretty deep look at Ethernet Wiring. But I'll try to explain it in simpler language. All three speeds (10, 100, 1000) run over the same physical wiring: Unshielded Twisted Pair (UTP). UTP is made up of 4 pairs of wires (8 total wires) -- each pair is twisted around each other. Each pair of wires work ...


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.


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


22

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 ...


21

Packets are long streams of binary numbers (zeros and ones). The zeros and ones are usually changes of an electric signal, specifically voltage changes. To simplify, suppose that 0 is 0 volts and 1 is represented alternatively as 5 volts and -5 volts. Then a long string of zeros and ones will look like this in terms of voltage variations in the cable: As ...


20

Only one device is allowed to transmit at any given time. At any other given time, another device is allowed to transmit. How can you have a conversation at a dinner table if only person can speak at any time?


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

The reasons for half-duplex ethernet are as you understand them. In fact, there was a movement to not include half-duplex for 1000Base-T, but it still made it into the standard. For 10 Gb ethernet, half-duplex was dropped so there is no such thing as 10 Gbps half-duplex ethernet as a standard. Unless you still have a hub (they are still around) or a ...


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....


18

Some LAN protocols, on some media, are half duplex. That means that only one host on a LAN can send a frame at any given time. The classic example of this is the original ethernet, but the modern example is Wi-Fi. The original ethernet ran on coax, and it used CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to detect collisions where two ...


17

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 ...


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 ...


17

Twisted pair uses differential signaling - in a pair, one wire is always the negative/complimentary signal of the other. In the simplest example, Transmit+ > Transmit- (higher voltage level) means 1 and Transmit+ < Transmit- (lower voltage level) means 0. Put in another way, each wire is a reference for the other. There is no reference to ground. For ...


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

The entire frame has to be at least 64 bytes. This is not just the payload, this includes the headers and the frame check sequence. The FCS takes up 4 bytes at the end. An Ethernet header consists of two 6 byte MAC addresses plus a 2 byte type field, 14 bytes in total. 64-4-14 = 46. IPv4 packets have an additional header of at least 20 bytes on top of the ...


14

That depends. While many Ethernet PHYs transmit data in a purely serial fashion (e.g. 100BASE-TX, 1000BASE-SX, 10GBASE-SR), some split the data stream into multiple lanes that are transmitted in parallel. Most commonly, 1000BASE-T - the common gigabit-over-copper variant - splits the encoded data stream into four lanes and transmits each separately on one of ...


14

A hub is really just a powered cable that repeats every signal it receives on one interface to all the other interfaces. If two devices transmit at the same time to the receive of the hub interfaces, the hub repeats both signals at the same time to the transmit of all the other hub interfaces, and both signals received will collide at the transmit of the ...


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 ...


13

Let's ignore the Gigabit part for now, and focus on your "2 devices are sending at the same time" part for a bit. On shared media, this can actually happen and be a problem. Most wireless transmissions are shared media, and Ethernet, back in the day, used to be: 10base2 (coax) used what was more or less a single cable with every one on it. Obviously, two (...


13

It's been done. I used to have a 300-baud acoustic layer 1 device.


13

To understand this you need to understand the historical context. Originally Ethernet used a shared coaxial cable. Only one device could successfully transmit on this at a time. If two devices transmitted at the same time it was considered a collision. Then repeaters came along, to extend the distance and increase the number of nodes. A repeater would ...


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

BASE indicates baseband signaling - there is no modulated carrier, the frequency starts near zero and extends to a certain cut-off frequency. BROAD indicates broadband modulation - there is a wide frequency band with a number of carriers modulated with the data (similar to xDSL). The X in -TX, -SX, ... stands for 4b/5b (100 Mbit/s) or (improved) 8b/10b line ...


12

This particular case is a complex one. Regarding 1000baseT. First: when we say in general that two devices are transmitting at the same time, they are not normally actually sending bits at the same instant on the same medium. If they do so, there is a collision and all the listening devices work this out (eventually, through various collision detection ...


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 ...


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