The general difference between Category 5e and Category 6 is in the transmission performance and extension of the available bandwidth from 100 MHz for Category 5e to 200 MHz for Category 6. This includes better insertion loss, near end crosstalk (NEXT), return loss and equal level far end crosstalk (ELFEXT). These improvements provide a higher signal-to-noise ratio, allowing higher reliability for current applications and higher data rates for future applications.

Because of its improved transmission performance and superior immunity from external noise, systems operating over Category 6 cabling will have fewer errors vs. Category 5e for current applications. This means fewer re-transmissions of lost or corrupted data packets under certain conditions, which translates into higher reliability for Category 6 networks compared to Category 5e networks.

The Connectors: Although Cat 6 and Cat 5e connectors may look alike, Cat 6 connectors have much better transmission performance. For example, at 100 MHz, NEXT of a Cat 5e connector is 43 dB, while NEXT of a Cat 6 connector is 54 dB. This means that a Cat 6 connector couples about 1/12 of the power that a Cat 5e connector couples from one pair to another pair. Conversely, one can say that a Cat 6 connector is 12 times less ‘noisy’ compared to a Category 5e connector. This vast improvement in performance was achieved with new technologies, new processes, better materials and significant R&D resources, leading to higher costs for manufacturers.

Source: www.tiaonline.org