400 Gigabit Ethernet is the latest and greatest standard of the Terabit Ethernet technologies, which are Ethernet standards with a transmission speed above 100 Gigabits per second.

Before adopting 400G, It’s crucial to understand 400G is available in two physical form factors: QSFP-DD and OSFP. So how do they compare?

Form Factors

OSFP “Octal Small Form-factor Pluggable” and QSFP-DD “Quad Small Form-factor Pluggable – Double Density” are very similar standards overall with a few standout differences.


  • Both are backward compatible with QSFP (40 or 100G) modules.
  • Both combine eight 50G lanes to achieve 400Gbps. 
  • Both are available in single-mode and multi-mode fiber variants.


  • QSFP (40 or 100 G) modules fit into QSFP-DD slots without the need for adapters, while OSFP requires a mechanical adaptor. 
  • OSFP is a physically larger connector with an integrated heat sink to facilitate a higher power draw and improved thermal management.
  • OSFP is built for future 800gbps compatibility in mind, while QSFP-DD has no plans for 800gbps support.

Who Needs It?

There is always a market for higher bandwidth, but who will benefit the most from 400G?

Higher Throughput

Network traffic is expected to grow nearly threefold by 2022. Large data centers and cloud providers like Amazon, Google, and Microsoft will be looking at these technologies. Service Providers on the other hand will need to update their backbones to keep up with these trends.

High Density

A single 400G port can break out to up to eight 50G connections, facilitating very high density in a single top of rack switch.

Who’s Selling?

All the major players are already releasing 400G equipment. So far we have seen releases from Cisco, Juniper, and Arista, with more to come.

  • Cisco has released a series of switches with QSFP-DD support.
  • Juniper has recently released new routers and switches with QSFP-DD support.
  • Arista technologies has released a series of switches with both QSFP-DD and OSFP support.
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