A QSFP28 (Quad Small Form-Factor Pluggable 28) transceiver typically operates by aggregating multiple lanes to achieve its maximum speed rating. The QSFP28 standard supports data rates of 25 Gbps per lane, and it aggregates multiple lanes to achieve higher overall data rates.  

The common configurations for a QSFP28 transceiver and their aggregated maximum speeds are:

1. 4 Lanes (4x25G):

• The most common configuration aggregates four lanes, each operating at 25 Gbps, resulting in an aggregated maximum speed of 100 Gbps.

• This configuration is often used for 100 Gigabit Ethernet (100GbE) connections.

2. 8 Lanes (8x25G):

• Some QSFP28 modules use eight lanes, each operating at 25 Gbps, resulting in an aggregated maximum speed of 200 Gbps.

• This configuration is used for 200GbE connections.

3. 16 Lanes (16x25G):

• In certain cases, QSFP28 modules may use 16 lanes, each operating at 25 Gbps, resulting in an aggregated maximum speed of 400 Gbps.

• This configuration is used for 400GbE connections.

It's important to note that the specific configuration and maximum speed of a QSFP28 transceiver depend on the design and intended application of the module. The configurations mentioned above are common in Ethernet applications, but QSFP28 modules can also be used for other high-speed data communication standards.

Always refer to the documentation provided by the manufacturer of the QSFP28 transceiver for accurate information on its configuration, supported data rates, and intended use cases. The maximum aggregated speed is achieved by combining the data rates of all the individual lanes supported by the module.