Just recently in Vancouver, the Ethernet IEEE-802.3cd Standards Committee voted yes simultaneously to include MicroQSFP, QSFP-DD and OSFP interconnect modules as MDI (media dependent interface) options. The remarkable singular vote, of 66 yes, 0 no, and 14 abstain, seemed to reflect the wide and deep need to support different types of new and established enterprise, datacenter and Cloud topologies, maintain rapid deployments and support the ever escalating bandwidth demand. Leaders of each of the three MSA organizations first presented a thorough interconnect proposal and took several specific questions and gave solid, informed answers before the vote was taken.
A question of maintaining three connection specifications preservation over time was asked. The answer is that the fairly documented three specifications will go into the SFF-xxxx connector specification process and preservation system. The SNIA trade group is negotiating to provide long term maintenance of the very large SFF-xxxx specification systems that has been developed by the sffcommittee.org formerly supported by the NCITS-T10, T12 standards organizations and used for over three decades.
These three interconnection systems support the roll out of Ethernet 1x50G, 2x50G, 4x50G, all using PAM-4 signaling. This is more of a signal integrity measurement challenge as this involves four electrical eye measurements versus the past popular NRZ signaling method using one electrical eye measurement. When some system designers choose external AOCs or pluggable modules, they may choose to use NRZ signaling from the transceiver chip to the bulkhead panel for better efficiencies.
Other standards bodies are heavily adapting the IEEE802.3 specifications and implementation of the 50G per lane applications. This includes InfiniBand and Gen-Z I/O interfaces as well as others with some differences. However, parts of the IEEE-802.3cd specification come from the OIF CEI-56G interface standard.
QSFP-DD and OSFP also support the almost released Ethernet IEEE-02.3bs 8x50G=400G standard. For the new single lane 50G PAM-4 IEEE802.3cd port interconnect option, people use the new SFP56 connector in some, one to one applications, but more usage with the QSFP56, MicroQSFP56 breakout style cables with multiple leg ends.
Each of the three interconnects are a full solution family with pluggable modules, AOCs, external passive and active copper straight and breakout cables, internal receptacle copper connector and cage, internal copper and optical flyover style passive cables and internal active copper flyover modules, options.
MicroQSFP is a 4-lane I/O connector that is much smaller than the QSFP28/56 type and has much better thermal performance for optical implementations. This much higher density ported face-plate solution works well connecting a top-of-the-rack switch with very high density server and storage blade arrays.
QSFP-DD is an 8-lane connector, slightly larger than QSFP28/56 but has twice the data transfer capability. It is a very efficient way to connect 400G one-to-one links between top of the rack, end-of-row and core switches. Also it is a very important solution for 8-legged break out cables for intra-rack and inter-rack toplogies.
OSFP is an 8-lane connector, slightly larger than QSFP-DD but has a slightly better thermal performance for hotter, higher wattage optical engines and transceivers. These very long reach type of connections were handled previously by the CFP thru CFP8 optical module families which takes up much more face-plate area per module compared to OSFP. Newer Cloud datacenters use many more very long reach links which was a primary factor in driving the new OSFP module usage. So, there are new switch types that have QSFP-DD and OSFP connector ports, sometimes along with MicroQSFP.
SFP56 and QSFP56 connectors and cables are also sometimes used for single link connections and break out cables, but are not on the IEEE-802.3cd spec yet. The COBO consortium’s DCN and Coherent modules/connectors spec is still in development and could be later added to the IEEE-802.3cd MDI option list.
Some OEMs, interconnect suppliers and datacenter end-users are already using these three interconnection systems in released products although the various 50G per lane standards are just starting to be readied for release. The rush to get 50G products, subassemblies, components and lab and production testing machines and networks to market could be seen even at last week’s OFC show in Los Angeles. You could say that these three interconnects compete in some applications, but voice of the customer market feedback is that all three usually serve separate application specific purposes.