Category 5, 5e, 6, and 6e are progressively enhanced specifications for the Ethernet over twisted-pair cables. These networking cables contain several pairs of wires twisted together in order to reduce signal interference. Ethernet cables typically use an 8P8C (eight positions, eight contacts) modular connector and a common wiring schematic referenced by the Telecommunications Industry Association.
Category 5 transmits at 100MHz frequencies, providing a rated line speed of up to 100Mbit/s and a maximum cable segment length of 100 metres (328 feet). Most Category 5 cables, designed for early networks, only used two twisted pairs. Older Category 5 cables continue to make up the bulk of the world's network infrastructure.
An improved specification to Category 5 was later introduced. By reducing noise and signal interference, Category 5e was capable of increasing rated transfer speeds to 350 Mbit/s over 100 metres (328 feet). The new standard also required all cables to include four twisted pairs (all eight contacts). An optimised encoding scheme allows up to 50 metre (164 feet) lengths of Category 5e cable to perform at, or near, Gigabit Ethernet (1000 BASE-T) speeds.
The mainstream adoption of Gigabit Ethernet (1000 BASE-T) required new industry-standard cables capable of transmitting at a higher frequency of 250 MHz. Category 6 cable uses thicker-gauge wire, increased shielding, and more pair twists per length to reduce signal noise and interference. The tighter specifications guarantee that 100 metre (328 feet) runs of Category 6 are capable of 1000 Mbit/s transfer speeds. 10-Gigabit Ethernet speeds are achievable when reducing cable lengths to less than 50 metres (164 feet).
Category 6 Enhanced (6e) is an augmented specification designed to double transmission frequency to 500 MHz. By wrapping Category 6e in grounded foil shielding, full 10-Gigabit Ethernet speeds can be reached without sacrificing the maximum cable length of 100 meters (328 feet).
Ethernet cable wiring specification
All Ethernet cables use either the T568A or T568B wiring standard. Mixing multiple cables is permitted, but using a different wiring standard on each end of a single cable will result in an Ethernet crossover cable.
T568A Pin 1 -- White/Green -- Pair 3, tip Pin 2 -- Green -- Pair 3, ring Pin 3 -- White/Orange -- Pair 2, tip Pin 4 -- Blue -- Pair 1, ring Pin 5 -- White/Blue -- Pair 1, tip Pin 6 -- Orange -- Pair 2, ring Pin 7 -- White/Brown -- Pair 4, tip Pin 8 -- Brown -- Pair 4, ring
T568B Pin 1 -- White/Orange -- Pair 2, tip Pin 2 -- Orange -- Pair 2, ring Pin 3 -- White/Green -- Pair 3, tip Pin 4 -- Blue -- Pair 1, ring Pin 5 -- White/Blue -- Pair 1, tip Pin 6 -- Green -- Pair 3, ring Pin 7 -- White/Brown -- Pair 4, tip Pin 8 -- Brown -- Pair 4, ring