Category 5e (CAT5e) cable, also known as Enhanced Category 5, is designed to support full-duplex Fast Ethernet operation and Gigabit Ethernet. The main differences between CAT5 and CAT5e can be found in the specifications. The performance requirements have been raised slightly in the new standard.
CAT5e has stricter specifications for Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT), Near-End Crosstalk (NEXT), Attenuation, and Return Loss (RL) than those for CAT5. Like CAT5, CAT5e is a 100-MHz standard, but it has the capacity to handle bandwidth superior to that of CAT5. CAT5 cable is typically used for Ethernet networks running at 100 Mbps or 1 Gbps
Category 6 (CAT6) cable provides higher performance than CAT5e and features more stringent specifications for crosstalk and system noise.
The quality of the data transmission depends upon the performance of the components of the channel. To transmit according to CAT6 specifications, jacks, patch cables, patch panels, cross-connects, and cabling must all meet CAT6 standards. The CAT6 components are tested individually, and they are also tested together for performance. In addition, the standard calls for generic system performance so that CAT6 components from any vendor can be used in the channel.
All CAT6 components must be backward compatible with CAT5e, CAT5, and CAT3. If different category components are used with CAT6 components, then the channel will achieve the transmission performance of the lower category. For instance, if CAT6 cable is used with CAT5e jacks, the channel will perform at a CAT5e level.