Here comes 5Gbps networking over standard cables

IEEE has approved the 802.3bz standard: 2.5Gbps over Cat 5e, 5Gbps over Cat 6.




A new Ethernet standard that allows for up to 2.5Gbps over normal Cat 5e cables (the ones you probably have in your house) has been approved by the IEEE. The standard—formally known as IEEE 802.3bz-2016, 2.5G/5GBASE-T, or just 2.5 and 5 Gigabit Ethernet—also allows for up to 5Gbps over Cat 6 cabling.

The new standard was specifically designed to bridge the copper-twisted-pair gap between Gigabit Ethernet (1Gbps), which is currently the fastest standard for conventional Cat 5e and Cat 6 cabling, and 10 Gigabit Ethernet, which can do 10Gbps but requires special Cat 6a or 7 cabling. Rather impressively work only began on the new standard at the end of 2014, which gives you some idea of how quickly the powers that be wanted to push this through.

The current mix of Cat 5e, 6, 6a, and 7a Ethernet outlets.
Enlarge / The current mix of Cat 5e, 6, 6a, and 7a Ethernet outlets.
NBASE-T Alliance
While Cat 6a and 7 are growing in popularity, the vast majority of homes, offices, and institutions use Cat 5e and Cat 6—and upgrading the cabling would be very expensive indeed. A wired 1Gbps connection is still fairly adequate for a single PC user, of course—but over the last few years, with the explosion of high-speed Wi-Fi, Gigabit Ethernet is now one of the bottlenecks. For example, the top end of the 802.11ac spec eventually calls for a total aggregate capacity of around 6.5Gbps; even current consumer 802.11ac gear, which maxes out at around 1.3 or 1.6Gbps, is running up against the limits of GigE




The new 2.5G/5GBASE-T standard (PDF) will let you run 2.5Gbps over 100 metres of Cat 5e or 5Gbps over 100 metres of Cat 6, which should be fine for most homes and offices. The standard also implements other nice-to-have features, including various Power over Ethernet standards (PoE, PoE+, and UPoE)—handy for rolling out Wi-Fi access points.



The physical (PHY) layer of 2.5G/5GBASE-T is very similar to 10GBASE-T, but instead of 400MHz of spectral bandwidth it uses either 200MHz or 100MHz, thus not requiring a super-high-quality mega-shielded cable. (This is the same reason that higher-bandwidth variants of DSL such as, only work over very short distances.) Other differences from 10GBASE-T include low density parity checking (LDPC) rather than CRC-8 error correction, and PAM-16 modulation rather than DSQ128.
Now that the standard has been approved, we won’t have to wait long for enterprise 2.5Gbps and 5Gbps Ethernet networking gear. What’s less clear is whether we’ll get consumer-grade 2.5Gbps equipment; we probably will, but not for a little while yet.