If you're installing an Ethernet network, you'll need to make a decision about the type of cable to use for the permanent connections between network jacks. For copper-based, twisted-pair networks, the four standards that are in common use today are Category 5, 5e, 6 and 6a. Category 5 is the oldest standard and Category 6a is the newest.
Category 5
Category 5 cabling has been used extensively since the 1990s as the standard cable for 10Base-T and 100Base-TX networks running at 10 and 100 Mbps, respectively. Category 5 cables have an impedance of 100 Ohms and a bandwidth of 100 MHz. The maximum length of a single cable run is limited to 100 meters, or 330 feet, which is the same for all Category 5 or 6 network cables.
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Category 5e
Category 5e cables share all the same basic specifications as Category 5 cables, however it reduces interference caused by crosstalk between the wires inside the cable. Category 5e cables use all four pairs of conductors, as opposed to the two pairs used to transmit data in 10 or 100-Mbps networks. As a result, a 1000Base-TX network using Category 5e cables can reach a maximum speed of 1000 Mbps, although this may be slower in distances over 50 meters.
Category 6
Category 6 cables replaced Category 5e cables as the preferred cables for 1000BaseTX networks because it could achieve full 1000 Mbps network speeds across a full cable length of 100 meters. This is possible because of its increased bandwidth of 250 MHz. Category 6 cables can also be used for 10GBase-T networks, for speeds of up to 10 GBps up to 50 meters.
Category 6a
Category 6a cables are enhanced versions of Category 6 cables, with an increased bandwidth of 500 MHz. Before the Category 6a standard became official, several companies marketed upgraded Category 6 cables as Category 6e cables. Category 6a is the official standard and its increased bandwidth can be used to achieve 10-Gbps speeds on 10GBase-T networks at the standard 100-meter maximum cable length.
Construction
All four types of cables are constructed with four pairs of 22 to 24 AWG conductors, with each pair twisted using a different number of turns per meter; this reduces the interference from neighboring pairs. An outer sheath of PVC for standard cables or fire-resistant plastic for plenum-rated cables covers all four conducting pairs. Category 6a cable is optionally available with a foil shield between the outer sheath and the inner conductors, which reduces outside interference and may increase network performance.