Category 6 - In June 2002 TIA approved specification for Cat 6 doubling Cat 5 bandwidth to 250 MHz. Cat 6 is backward compatible with lower Category grades and supports the same Ethernet standards as Cat 5e.
Currently there are no Ethernet standards that take advantage of Cat 6. ANSI/TIA854 is working on 1000Base-TX. When complete this standard will use two pair in each direction as opposed to all four for 1000Base-T over Cat 5e. This is expected to reduce the cost of Gigabit Ethernet implementations. 1000Base-TX will only operate over Cat6.