The physical 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 or, the transfer rate drops to 2.5 or 5 Gbit/s, respectively. The spectral bandwidth of the signal is reduced accordingly, lowering the requirements on the cabling, so that 2.5GBASE-T and 5GBASE-T can be deployed at a cable length of 100 m on unshielded Cat 5e and Cat 6 cables, respectively. The IEEE Standard 802.3bz defines:
Unlike the preceding 10GBASE-T standard, equipment manufacturers have indicated their intention to implement 802.3at type Power over Ethernet on certain types of NBASE-T switches. This implementation is intended to support high-bandwidth wireless access points which exceed the speed capabilities of existing 1000BASE-T Power over Ethernet connections.
Comparison of twisted pair based Ethernet technologies
Name
Speed
Lanes per direction
Bits per cycle
Spectral bandwidth
Required cable
Cable rating
10
1
1
10
Cat 3
16
100
1
3.2
31.25
Cat 5
100
1,000
4
4
62.5
Cat 5
100
4
6.25
100
Cat 5e
100
4
6.25
200
Cat 6
250
4
6.25
400
Cat 6A
500
History
The intermediate speeds became relevant around 2014 as it became clear that it would not be possible to run 10GBASE-T over the Cat5e cable that had been used for the wiring in many buildings but that, with the development of fast WiFi protocols such as IEEE 802.11ac, there was a significant demand for cheap uplink faster than 1000BASE-T offered. IEEE 802.3bz will also support Power over Ethernet, which has generally not been available at 10GBASE-T. As early as 2013, the Intel Avoton server processors integrated 2.5 Gbit/s Ethernet ports. Whilst Broadcom had announced a series of 2.5 Gbit/s transceiver ICs, 2.5 Gbit/s switch hardware was not widely commercially available at that point; 10GBASE-T switches do not generally support the intermediate speeds. In October 2014, the NBASE-T Alliance was founded, initially comprising Cisco, Aquantia, Freescale, and Xilinx. By May 2015, it had expanded to 34 members covering most producers of networking hardware. The competing MGBASE-T Alliance, stating the same faster Gigabit Ethernet objectives, was founded in December 2014. In contrast to NBASE-T, the MGBASE-T says that their specifications will be open source. With the forming of the IEEE 802.3bz draft standard under the patronage of the Ethernet Alliance in June 2015, the two NBASE-T and MGBASE-T Alliances are forced to collaborate. IEEE 802.3's "2.5G/5GBASE-T Task Force" started working on the 2.5GBASE-T and 5GBASE-T standards in March 2015. On September 23, 2016, the IEEE-SA Standards Board approved IEEE Std 802.3bz-2016.
