The most widely used network cables are Ethernet cables. Ethernet is a frame-based transmission standard that has been revised several times. The original Ethernet specification was designed for 10 Mbs data rate, but then was later revised to support 100 Mbs data rate under the Fast Ethernet standard. Today, there is also Gigabit Ethernet that can reach data rates of up to 1000 Mbs. CAT5 (5 is for fifth generation) is the most widely used cables for Ethernet networks and supports Fast Ethernet data rates of up to 100 Mbs. For Gigabit Ethernet, it is necessary to use CAT6 cabling. CAT6 is significantly more expensive that CAT5, but it is compatible with CAT5 networks and therefore is a good choice for future upgradeability.