While QSFP28 (Quad Small Form-Factor Pluggable 28) is designed to support higher data rates, it is backward compatible with QSFP+ (Quad Small Form-Factor Pluggable Plus), which operates at 40 Gigabit per second (Gbps). QSFP28 is an evolution of the QSFP form factor and supports data rates of 100 Gbps and higher. 

Here are some key points:

1. Backward Compatibility:

• QSFP28 ports are typically backward compatible with QSFP+ modules. This means that you can use a QSFP+ module in a QSFP28 port, and the link will operate at the maximum data rate supported by the QSFP+ module, which is 40 Gbps.

2. Port Configuration:

• If you have a network device with QSFP28 ports, you can use QSFP+ modules to achieve 40 Gbps connectivity. This can be useful in scenarios where you have existing QSFP+ equipment or if you need to migrate to higher data rates gradually.

3. Higher Data Rates:

• While QSFP28 can support data rates beyond 40 Gbps, its ability to operate at 40 Gbps is maintained for backward compatibility. This allows for flexibility in network deployments.

4. Consideration for Future Upgrades:

• If you have a network infrastructure that supports QSFP28, it provides the capability to upgrade to higher data rates, such as 100 Gbps or 200 Gbps, by using QSFP28 modules when needed.

Always check the specifications and compatibility of your networking equipment to ensure proper functionality. Additionally, refer to the documentation provided by the equipment manufacturer for accurate information on supported module types, form factors, and data rates.