IEEE 802.3bz, NBASE-T and MGBASE-T are standards released in 2016 for Ethernet over twisted pair at speeds of 2.5 and 5 Gbit/s. These use the same cabling as the ubiquitous Gigabit Ethernet, yet offer higher speeds. The resulting standards are named 2.5GBASE-T and 5GBASE-T.
NBASE-T refers to Ethernet equipment that supports speeds of at least 2.5 Gbit/s and sometimes 5 or 10 Gbit/s, and that can automatically use training to operate at the best speed supported by the cable quality. Usually it also supports additional link speeds (10, 100 or 1000 Mbit/s) in connection with autonegotiation, depending on the capabilities of the equipment at the other end of the cable.
Technology
These standards are specified in Clauses 125 and 126 of the IEEE 802.3 standard. The physical (PHY) layer transmission technology of IEEE 802.3bz is based on 10GBASE-T, but operates at a lower signaling rate. By reducing the original signal rate to 1⁄4 or 1⁄2, the link speed drops to 2.5...