In 1972, during his employment at PARC Xerox, Bob Metcalfe pitched his vision for an interconnected 'Ethernet' (Figure 1). Though he was a visionary, it seems unlikely that he could have imagined the impact his idea would have.
Metcalfe’s original vision was to provide shared access to a printer from a pool of computers (Figure 2). As we all know now, Ethernet has in the past 40+ years evolved to be much more than that.
The first PARC Xerox implementation operated on a link speed of 3Mbps on a shared coaxial media. The path to a broad acceptance and mass deployment was secured in 1983 when an IEEE workgroup was set. This workgroup is called 802.3 and is responsible for the standardization of optical fiber and copper media for various link speeds. Figure 3 shows the standardization timeline initiated by the 10Mbps link speed in 1983 evolving through 100Mbps, GbE, 10GbE, 40GbE, 100GbE to 400GbE including future 50GbE and 200GbE speeds. Historically, the technologies deployed in the different Ethernet generations have been reused from other standards as with the Fiber Channel for the GbE generation.
Changes to Meet Ethernet Demands
A new era in the Ethernet ecosystem dawned with the standardization in 2010 of 40GbE, as it broke the previously applied 'rule' that the next generation link speed was 10x the previous speeds. The 40GbE standard simply deployed the already available 10Gbps transceiver technology from 10GbE on four channels, marking the beginning of the QSFP track QSFP -> QSFP+ -> QSFP28 ->. To learn more about QSFP, see Figure 4.
When the four-channel 100GbE standard came along in 2015, it necessitated the development of new 25Gbps transceiver technology. This was deployed for the first time with the CFP4 form factor and later in the QSFP28.
It was a major change for IEEE to deviate from the previous 10x link speed increase between neighboring link speed standards, but this was nothing compared to what was to come. With the introduction of the new 25Gbps transceiver technology, major players representing the full value chain from the device vendors to service providers formed an industry consortium promoting the use of the new 25Gbps transceiver technology in a single channel 25GbE Ethernet standard. They also promote a dual channel 50GbE Ethernet standard (see Figure 5 below). The clear ambition with the new initiative was to bypass the IEEE bureaucracy and quickly 'help themselves' to low-cost technology that, by simple means, would increase the bandwidths of existing datacenter fiber infrastructure. A truly revolutionary move that has never been seen before in the Ethernet 'universe' and has been an eye-opener for IEEE.
On the Horizon
The breakthrough TbE link speed 'landmark' requires support from technical elements that have not yet been determined – but don’t be lulled into complacency. It’s only a matter of time before the world of Ethernet will take us there, by hook or by crook. In the next instalment of this series, we’ll look at the longevity and upgradability of future-proof FPGA platforms.