SFP28

SFP28 carries a single 25 Gb/s lane in the SFP footprint. It emerged from the 100GbE work — one lane of a 4×25G QSFP28 — and made 25GbE the natural server uplink, replacing 10G at nearly the same cost per port.

Key facts

Specifications

• SFF-8402 — SFP+ 1X 28 Gb/s Pluggable Transceiver Solution (SFP28): the

mechanical and electrical definition of SFP28.

• SFF-8432 — Module and Cage (shared with SFP+).
• SFF-8472 — Management Interface.
• IEEE 802.3by — the 25GbE PHY and the 25GAUI electrical interface.

Management interface

Two-address SFF-8472 as with SFP+ (A0h identity, A2h diagnostics), with 25G rate and interface codes from SFF-8024. Forward error correction options (no FEC / BASE-R / RS-FEC) matter at 25G: a mismatch between host and module settings is a classic cause of a link that will not come up.

Compatibility notes

• Backward compatible: an SFP28 port accepts SFP+ and SFP modules at their own rates.
• Four SFP28 links are the breakout of one QSFP28 port (4×25G) — see

QSFP28.

In CodingBox

Fully supported per SFF-8472 — identity, DDM with thresholds, editing and writing with checksum recalculation. SFP28 identity fields are decoded with the 25G codes so the Check transceiver screen reports the correct interface.