Yes. A QSFP (40G or 100G) module can be inserted into an OSFP port by using a simple, completely passive, mechanical adapter. This adapter is available from Arista, with part number ADPT-O-Q-100G. The adapter and the adapter with a QSFP plugged into it, are shown below.
When using a QSFP module in an OSFP port, the OSFP port must be configured for a data rate of 100G (or 40G), instead of 400G.
The QSFP-DD port (the cage) is backward compatible with the QSFP transceiver: we will be able to plug a QSFP28 into a QSFP-DD port (if the switch support it).
While there is no direct thermal management mechanism (no integrated heat-sink), the QSFP-DD allows a maximal power consumption of 12 watts (initial spec), challenging the transceiver industry to release a 400G technology not exceeding that. Recently, the QSFP-DD MSA Group has published an application note confirming the 15W feasibility, while the last specification (in its version 4.0) defines a Power Class 7 (up to 14W) and a Power Class 8 (>14Watts).
OSFP – stands for Octal SFP – 8x 50G =400G
The OSFP is standardised by the OSFP MSA (https://osfpmsa.org/). Its size is slightly bigger than a
QSFP module and is designed for 8 data lanes, actually reaching 400G bitrates (with 50G PAM4). It
has a direct thermal management (integrated heat-sink) and allows a maximum power consumption
of 16 Watts, relaxing the requirements for the transceiver industry. The OSFP cage backward-
compatibility toward QSFP module is only feasible with an adapter.
Arista Networks, a promoter of the OSFP, also claims that OSFP can go up to 20 Watts thermal
capacity, opening the door for Coherent DWDM transmission.
The key names behind the 2 form factors
Interestingly, key companies are behind the QSFP-DD MSA Group and OSFP MSA, while some are supporting both standards:
At the release date of this article, some switch vendors have announced/released “400G ready” switches with either QSFP-DD or OSFP ports*:
- Arista – 7060DX4-32 supporting OSFP and 7060PX4-32 supporting QSFP-DD
- Cisco – Nexus 3K and 9K supporting QSFP-DD
- Edgecore – AS9716-32X supporting QSFP-DD
- Huawei – NetEngine 9000 – 8*400G-QSFP-DD supporting QSFP-DD
- Juniper – PTX10003, QFX 5220 and QFX10003 supporting QSFP-DD
- Nokia – 7750 SR supporting QSFP-DD
* the list is not exhaustive and is likely to change rapidly and frequently.
1U Rack – 32 or 36 ports?
Both QSFP-DD and OSFP remain “compact” for access and data-centre applications. However a 1U rack can handle maximum 32x OSFP ports, while the same rack can handle 36x QSFP-DD ports. More density with QSFP-DD but also more challenges in term of power dissipation.
