For years we've used multiple Ethernet devices with a maximum speed of one gigabit per second. Reaching that speed depends not only on hardware but also on cabling, and believe it or not, the "gigabit per second" is about to become a bottleneck. The new 802.3bz standard aims to take the next step, raising the maximum to 2.5 gigabits per second with Cat 5e cables, and 5 gigabits per second over Cat 6 cables.
Why a new standard?
My old Linksys WRT54G is still the main router in my house, which means the maximum transfer speed for physical links is 100 megabits per second. That's more than enough if we consider that my "BitTorrent box" has been offline for months. Replacing hardware is not a complex problem, but the situation is very different when we talk about cabling. Many offices and factories have Cat 5e cables that haven't been certified for higher specifications. In other words, the famous "gigabit per second" is not within everyone's reach, and the next step, 10GBASE-T, is even more difficult. This is why a new standard was needed as a "bridge" to reuse existing installations. This brings us to the 2.5GBASE-T and 5GBASE-T modes, both under the 802.3bz specification.
How it works
Basically, the standard establishes a maximum speed of 2.5 gigabits per second with Cat 5e cables, and 5 gigabits per second with Cat 6 cables. The base (or "physical layer") for the 2.5GBASE-T and 5GBASE-T modes comes from the aforementioned 10GBASE-T. The amount of "bits per Hertz per channel" remains at 6.25, but the spectral bandwidth reduces to 25 percent in 2.5 gigabit connections (100 MHz), and to 50 percent in 5 gigabit connections (200 MHz). Since they don't meet the specific requirements of 10GBASE-T, the cables don't require as much shielding and protection. The standard also includes optimizations for other functions, including PoE.
Approval and impact
802.3bz was approved in what many see as record time, which highlights the need for the new standard. Maximum speeds in wireless connections have skyrocketed, placing "gigabit Ethernet" on a lower level. With a simple hardware replacement, installations around the world will be able to access higher transfers and postpone for longer the costly investment associated with replacing all cables, which can amount to hundreds of thousands of dollars in certain places.
