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I was just wondering if a single bit travels with the same physical speed through the same type of wire of a 10 Mbit network as through a 10 Gbit network?

As far as I know a single bit has the speed of 2/3 of the speed of light through copper, the faster the network the more bits can be transmitted simultaneously (bandwidth), but the single bit does always have the same speed, is that correct?

And does the type of wire have an influence, Cat.5 vs. Cat6/7?

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closed as off topic by random Oct 31 '11 at 14:33

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2 Answers

Electrons travel at the same speed on both 10Mbit and on 1000Mbit media. The difference between 10Mbit and 1000Mbit devices is that 10Mbit devices have to keep a certain voltage level on the wire for a longer time period. So in the same time window a 10Mbit device puts a signal on the network, a 100Mbit puts 10 times that and a 1000Mbit puts 100.

What I think that influences the speed of a signal is Impedance and resistance and that is why higher category cables have lower resistance/100m. Also higher category cables have to be able to support frequencies in the range 1-100MHz and within that range the cable must generate less echo/crosstalk effect than certain values specified in IEEE 802.3. Cat5 can be used for 10 and 100mbit Ethernet and Cat5e and higher can be used for 1000Mbit cables. AFAIK, using Cat6 for Fast Ethernet is an overkill, but is very common for Gigabit installations.

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Resistance is the same for the same length of wire of a given diameter. What can vary is the impedance (and consequently capacitance), which is dependent on the geometry and construction of the wire pairs. –  Ignacio Vazquez-Abrams Oct 31 '11 at 10:11
...and inter-wire inductance. –  Linker3000 Oct 31 '11 at 12:49
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Due to the various encodings used, no, single bits in each technology do not propagate at the same speed. Manchester and MLT-3 in particular use the entire timeslice to transmit the bit.

The grade of cable determines the maximum "safe" frequency range that can be filled by signals traveling down it; signals with a higher frequency are likely to be attenuated, causing them to possibly be undetectable at the other end.

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