Completing an Ethernet specification takes years of effort. Just ask John D’Ambrosia of Futurewei who has spent the last 15 years chairing various IEEE Ethernet standards.
John D'Ambrosia
He oversaw the standardisation of 40/100 Gigabit Ethernet (GbE) and of 200/400GbE and he is now chairing two IEEE Task Forces standards addressing 100 and 400 coherent Ethernet.
He is also the Chair of the group looking at new Ethernet applications (NEA) or to give it its full title, the IEEE 802.3 Industry Connections NEA Ad Hoc group.
D’Ambrosia is driving the development of the ‘Beyond 400 Gigabit’ Call-for-Interest work of the NEA group that will define the next Ethernet standard.
Start the clock
The IEEE 400 Gigabit Ethernet (GbE) standard took four-and-a-half years and was completed in late 2017.
One year later a study began looking at key bandwidth drivers to help inform the choice for the next Ethernet standard, knowing that once started, it would take at least four years to complete. The Ethernet Bandwidth Assessment report was published in April.
Bandwidth drivers, taken from the IEEE 802.3 Industry Connections NEA Ad Hoc group's Ethernet Bandwidth Assessment report.
D’Ambrosia says that from early conversations, there are industry voices that back 800GbE while others favour 1.6TbE: “Some of us looking at these issues are saying: ‘Which one makes sense?’ Maybe it is both.”
What is clear, he says, is that work to define the next Ethernet standard needs to start now.
Industry developments
Several technology developments in the last year highlight how the industry is already moving beyond 400 gigabits.
Operators have started deploying the first coherent transport systems from Ciena, Huawei and Infinera supporting 800-gigabit coherent transmissions.
The Ethernet Technology Consortium has issued an 800GbE media access control (MAC) and Physical Coding Sublayer (PCS) specification based on 100-gigabit electrical interfaces.
Two 800-gigabit optical multi-source agreements (MSAs) have also been announced: the 800G Pluggable MSA developing optical specifications for 800-gigabit pluggable modules, and the QSFP-DD800 MSA that extends the double-density form factor to 800 gigabits.
“I believe people will want 800GbE if they have an 800-gigabit module,” says D’Ambrosia.
The OIF has also started its next electrical interface specification work to enable 224-gigabit lanes. This would narrow the electrical lanes needed for any future Ethernet standard.
The 800GbE could also be used as an 8x100-gigabit interface which would need to be accommodated. But historically, the industry has favoured four-wavelength solutions which aligns with four 224-gigabit electrical lanes.
For 400GbE, 8x50-gigabit and 4x100-gigabit electrical interfaces were selected. A 4x100-gigabit interface was used for distances up to 500m, while 8x50-gigabit was chosen for 2km and 10km. And a 4x100 interface is also underway in the IEEE 802.3ck project, says D’Ambrosia.
Given expected traffic growth, the development of an 800GbE module may be insufficient by the time the work is completed, which explains the interest in 1.6TbE as the next Ethernet standard. A 1.6TbE specification would require eight lanes based on a 224-gigabit electrical interface, and would likely be completed in 2026 or 2027 at the earliest.
“The problem is that a rate without economics is dangerous,” says D’Ambrosia. “We need to have cost-efficient bandwidth, not just bandwidth.”
D’Ambrosia is leading an effort in the IEEE 802.3 NEA to develop the Call-for-Interest to form a Beyond 400GbE, Study Group. Based on recent discussions, the Study Group could be formed in the first quarter of 2021.
800GbE versus 1.6TbE
It’s unfair to ask D’Ambrosia what the next Ethernet speed will be given that the specification work has yet to start.
Historically, there was a consensus to develop 100GbE although there was a fierce debate to include 40GbE. Industy consensus also existed at 400GbE given that 1TbE was deemed a step too far.
Large-volume deployments of 400GbE have yet to happen despite the IEEE standard having been completed several years ago. However, 400GbE deployments will happen quickly once it starts, says D’Ambrosia. But even then, a significant portion of 400GbE deployments will likely be as a break-out design of four 100GbE lanes.
The choice of the next Ethernet speed this time is less clear.
Does 800GbE provide the industry with a sufficient bandwidth jump? Equally, like Terabit Ethernet, 1.6TbE may be a step too far given the technical challenges and cost. The debate is still open: either approach could be adopted, or both, says D’Ambrosia.
“Based on the findings of the Ethernet Bandwidth Assessment, as well as the realisation that the industry has much to discuss and develop, the time for the Call for Interest for the next rate of Ethernet is now,” he says.
That is because switch chips are doubling in capacity every two years, the 224-gigabit electrical interface will appear in 2025 at the earliest. And since it will take at least four years to develop the next Ethernet standard, the clock is ticking.