The Race to 400G Ethernet Part 4

The Race to 400G Ethernet Part 4

By: Dave Fredricks | Data Center Infrastructure Architect

This is the final installment of my four-part series tracking the technology advancements in the move from 100G to 400G Ethernet speeds and its effects on structured cabling. You can find links to the previous three installments below.

The need for speed

The main benefit for the move from 100G to 400G speed is the connection between the spine and leaf (two tier) switches. 400G also increases the speed to servers and compute equipment from the leaf switch, going from 10G/25G up to 100G.

As data center operators are supporting hyperscale, cloud, artificial intelligence (AI), machine learning and IoT to name a few technologies, the higher bandwidth will aid with reduced latency. This will especially be beneficial for IoT usage and edge computing as it will require less latency and quicker connections to properly support user devices.

The Institute of Electrical and Electronics Engineers (IEEE) released the standard 802.3bs that introduced 200 Gb/s and 400 Gb/s Ethernet on December 12, 2017. Within 802.3bs are two multi-source agreement (MSA) groups working to offer the new 200G and 400G optics. They are OSFP,  and QSFP-DD. The OSFP MSA group is driven by Arista and the QSFP-DD group by Cisco.

A huge advantage of 400G is that it reduces the cost of 100G ports as breakouts (or 400G = 4x 100G).

Arista and Cisco have a big say

Arista and Cisco are two dominant vendors in the Ethernet networking space that are offering 400G networking equipment.

Arista announced on October 23, 2018, the release of 400G platforms and optics. Arista’s 400G switches - have the capability to work with both the OSFP and QSFP-DD optic. Both style optics are standards based (IEEE 802.3bs) and will work with other vendors equipment who support standards based optical transceivers. Cisco is also in the 400G space with its latest networking hardware and optics as announced on October 31, 2018.

While Arista network switches will work with both the OSFP and QSFP-DD style optics, Cisco’s gear will only work with QSFP-DD type as of today. Cisco is also working on a new 400G optic called Bi-Directional or BiDi that works similar to their current offering of the QSFP-40/100-SRBD®.

One of the benefits with the BiDi is that it uses existing installed data center cabling meaning an LC connection into the optic. One of the draw backs with the BiDi is that it might be proprietary and only work connecting Cisco equipment.

The right cable and connector for the job

For the data center operator there are four cabling or connector options to consider that support the new 400G optics. For in-cabinet connections of 3 meters or less direct attach copper (DAC) cables are available. For in-row connections or longer distances active optical cables (AOC) are available. For distances of 3 meters to 500 meters two connectors are available.

First is the new MPO/MTP® 16 fiber multimode connector as shown below from USConec®. This connector supports 400G up to 100 meters.

Notice that the alignment key on top is off set and different than the traditional 12- and 24-fiber MPO/MTP® MPO/MTP® connector where the key is located in the center. Meaning that the new 16-fiber connector will not mate with the 12- or 24-fiber connectors.

Operators can connect the new 16-fiber connector into existing 12- or 24-MPO/MTP® fiber cabling plants using a hybrid breakout harness. One end with the 16-fiber connector into two ends with 8-/12-fiber connector which would plug into common 12-fiber MPO/MTP® structured cabling systems.

The second connector to be used is an MPO/MTP® 8-fiber singlemode connector as shown below by USConec®. This connector supports 400G up to 500 meters. This connector is common and has the alignment key in the center. Where the multimode MPO/MTP® 16-fiber connector on OM4 fiber can go up to 100 meters the MPO/MTP® 8-fiber singlemode connector can go up to 500 meters on OS2 fiber.

Should I stay or should I go: Singlemode vs. Multimode

As the new 400G optics become readily available in 2019 monitoring the cost will help data center operators decide on whether to consider moving to singlemode fiber over multimode fiber with new applications.

Traditionally singlemode optics are much more expensive than multimode optics. But, that gap has been narrowing over the past several years especially with the introduction of the 100G PSM4 optic. The PSM4 optic, uses the same MPO/MTP® 8-fiber singlemode connector as will the 400G.

The point to be made is this. If you are looking at a new network project with 100G spine and leaf (two-tier) topology consider using singlemode fiber now with 100G PSM4 optics. This cabling will transition to 400G with no modification.

As 800G is now being discussed, the good news is that this connector looks to work for that next generation speed with no modification.


We can help you with this

At CABLExpress we offer, at no cost, cabling design assistance that includes a visio drawing of every cabinet or rack in the data center space whether it’s three cabinets or 300. Once a Visio drawing is completed to meet the application and approved we will create a specific bill of materials with cost. This bill of materials can be used to price other vendors to compare solutions equally. If you are looking at an upcoming Ethernet or Fibre Channel project, consider a proposal from CABLExpress.

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