RJ45 Connector Pin-out for EIA/TIA 568A Standard
The T568A straight configuration dates back to 1995 and is largely obsolete.
It is incompatible with the more recent T568B standard unless used as a crossover cable.
The crossover cable is wired T568A on one end and T568B on the other end.
RJ45 Connector Pin-out for EIA/TIA 568B Standard
The T568B straight configuration is the current wiring scheme for Ethernet cabling.
The exception would be for the crossover cable which is wired T568A on one end and T568B on the other end.
For more detailed information visit wikipedia.org/wiki/TIA/EIA-568