Eye on Standards: Four 400G quandaries to look forward to

October 01, 2014 // By Ransom Stephens, EDN
The 400 GbE (that’s Ethernet at 400 Gbits/sec to you and me) task force has convened and hopes to deliver a 400GbE specification in Q1 of 2017. At this time, everything is on the table.

In 400G Ethernet Effort Begins, John D'Ambrosia, Chair of the Ethernet Alliance and 400G Ethernet Group, said, "The key part is that this initial effort will spend significant time and energy on defining an architecture that will be flexible and enable future 400GbE implementations." He went on to say that, "diving into the technical details of each of these anticipated proposals will be part of the fun that awaits those ready for this project."

Back in 2007, the IEEE 802.3 High Speed Study Group realised that the data rate needs of networking and computing have been increasing at different rates (Figure 1); Moore's Law scaling of 2x every 18 months for networking and 24 months for computing. So even though the 100 Gbit/sec spec is still somewhat incomplete, the technology is being rolled out and it's not hard to see the demand for 400 Gbit/sec links coming on the horizon.

Figure 1. Core networking and server i/o demand projections from 2007 show that networking speeds are increasing at a faster rate than computing speeds. Source: IEEE 802.3 HSSG.

Among its goals, the 400G working group hopes to maintain backward compatibility, preserve Ethernet frame formatting, support OTN (optical transport network), and specify EEE (energy efficient Ethernet) as an option.

In addition to increasing the media access (MAC) rate by a factor of four over 100 GbE, the IEEE 802.3bs 400 GbE group plans include the following four quandaries.

Next; BER goes to 1E-13