Towards 800G and 1600G Ethernet

New Standards for 800G Ethernet

Coherent 400ZR optics is a key driver of 400 GbE in data centers by interconnecting regional data centers using DCI (Data Center Interconnect) by transporting Ethernet directly on coherent links. Currently there are some proprietary 800G per wavelength coherent optic transceivers already available. However, for interoperability, the Optical Internetworking Forum (OIF) is now working to define 800ZR to address DCI applications and 800G-LR to address single wavelength coherent up to 10 km for campus applications.

As hyperscale data centers look for more bandwidth and start to deploy 400 Gigabit Ethernet (GbE) links in their spine networks, there are already moves towards a new 800 GbE standard. The industry is already deploying 2×400 GbE (an aggregate of 800G) in QSFP-DD800 and OSFP form-factors in support of 25.6 Tb switches and line cards. The Ethernet Technology Consortium (ETC) has defined an 800 GbE standard based on dual instance of 400 GbE PCS/FEC. In addition, 800G pluggable transceiver modules have been specified by the 800G Pluggable MSA, the QSFP-DD MSA and the OSFP MSA.

The ETC 800 GbE Standard and New IEEE 802.3 800/1600 GbE Standards

So, what is the status of 800G standard development? Currently, the IEEE 802.3 has formed the 802.3df task force to specify 800 GbE and 1600 GbE. The IEEE 802.3df task force development can be categorized in to three main projects:

1. Define 800/1600 GbE MAC, PCS, and FEC. Define PMDs in support of 800 GbE, such as 800-KR/CR, 800G-SR8 (100 m), 800G-DR8 (500 m), 800G-FR8 (2 km), 800G-LR/LR8 (10 km), and 800G-ER/ER8 (40 km).
2. A major effort will be to define new 200G per lane optical PMDs. Define PMDs such as 800G-DR4 (500 m), 800G-FR4 (2 km), and 800G-LR4 (10 km).
3. A major effort will be to define 200G per lane electrical IOs. Define PMD such as 200G-KR/CR, 1600G-DR8 (500 m), 1600G-FR8 (2 km), 800G-LR (10 km), and 800G-ZR (80 km).

IEEE 800G standards cover 8x100G using multimode fiber for up to 100 m, 8x100G parallel single-mode fiber for up to 500 m, and 8x100G wavelength division multiplexing (WDM) over single-mode fiber for up to 2 km and 10 km. Followed by more efficient PMDs based on 200G per lane. IEEE 802.3df needs several years to develop new Ethernet standards beyond 400G, so the Ethernet Technology Consortium stepped in to define an 800 GbE MAC/PCS standard based closely on the existing 400G Ethernet. By simply doubling the number of FEC/PCS VL (virtual) lanes (from 16 to 32), a new media access control (MAC) has been specified that is eight by 106.25 Gbps and operates at 800 GbE. By mostly leveraging the 400G IEEE 802.3bs standard, the Ethernet Technology Consortium saved considerable time and effort in developing the new 800G specification that they are calling 800G-ETC-R (to differentiate it from any future IEEE standard).

The following figure shows the high-level architecture of an Ethernet Technology Consortium 800G interface. The MAC has been scaled up to 800G, but there are two physical coding sublayers with forward error correction (FEC) from the 400G Ethernet standard that have only been slightly modified. The MAC distributes data across 32 lanes to the two PCSs, 16 lanes of 25 Gbps data to each PCS. Modified alignment markers are inserted into each PCS data lane to ensure that an 800G data stream can be received and processed. The 32 PCS lanes are then multiplexed in the Physical Medium Attachment (PMA) layer to feed eight 106.25 Gbps lanes to the Physical Medium Dependent (PMD) layer.

The challenge the industry is now facing is to adopt ETC 800 GbE PCS/FEC, which has 32 VLs, or define a more efficient PCS/FEC in the IEEE 802.3df based on 8 VLs for 800 GbE and 16 VLs for 1.6 TbE.