As the title suggests, Does a longer Ethernet cable slow your connection down?
Ethernet Cable Length – Does a Longer Ethernet Cable Slow Your Connection?
cableethernetlayer1
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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 be implemented in a standard way so that anyone who works on it will intuitively understand what they are working on.
For instance, imagine if someone used your reversed wiring in a real environment, left, and you were now troubleshooting a cabling issue at that site. On inspection, you determine the cable is damaged and it need to be re-terminated on one side and did so with the standard TIA/EIA-568B. After doing so, the cable still will not work.
It isn't because your termination is bad, but because the cable is now a rolled cable. You may waste additional time/resources on trying to re-terminate the cable additional times. Unless you use a cable tester, you may not easily figure out that the cable is now a rolled cabled.
Ultimately, this potentially causes more problems/downtime and isn't really justifiable by any possible reason the original person may have had to not follow the standard.
Old answer (thinking the OP was talking about using TIA/EIA-568B on one side and the reverse on the other):
What you are describing is what is often referred to as a "rolled" or "rollover" cable. Pin 1 connects to pin 8 on the other side, pin 2 to pin 7, etc.
This type of cable would not work for network communications, but is used by many vendors for serial communication, such as console port access.
My suggestion would be to wire the socket as a single connection and then if you later decide to use it as two cables, just use a splitter (a little piece of cable with one plug and two sockets) at both ends. Just make sure to get a splitter for Ethernet (which connects two pairs to one socket and two to another) and not ISDN (which just connects both sockets in parallel).
Connecting the wires to two sockets in parallel may cause signal problems for the gigabit connection and you (or someone else) will forget to use it correctly at least once and plug one end of the cable as a single connection while connecting two computers at the other end.
Upd.
Internal wiring of ethernet splitter
Splitter kind 1, kind 2 useful for patchpanel
Best Answer
The electric signal will be slowed down by a minimal amount (afterall it travels at 2/3 light speed, more exactly at 0.64c, the velocity factor), how much time does light take to travel for 100 meters?
So it just takes an extra 0.00052 milliseconds which is just 520 CPU cycles (on a 1 Ghz CPU).
However the longer the cable the weaker the signal becomes, once the signal is weak enough it will starts to lose bits of information because of interferences, each time a bit is lost, something in the network layer sees that a checksum/parity check fails, and ask for that packet again.
Asking for a new packet will take a very long time.
So as long as signal is strong in the cable, the slowdown would be minimal (it is greater than I expected anyway).
Once you start losing information because cable too long, the slowdown would greatly increase.
Also note that certain communications protocols are timed, so if the cable is too long it may not even be usable because it would go out of sync (that's a by-design issue)