Uplink port and forward error correction

The HPE Virtual Connect SE 100Gb F32 Module for HPE Synergy supports various transmission speeds. When a transceiver is inserted in an uplink QSFP port, the interconnect module applies a port configuration from HPE OneView. The speed is then set to a fixed value or set to auto negotiate with the second device. Hewlett Packard Enterprise recommends the use of Forward Error Correction (FEC) for 25G and 100G speeds.

FEC is a technique that controls errors during data transmission. The source (transmitter) encodes the data and the destination (receiver) recognizes and corrects the errors without requiring a retransmission.

The need for and use of FEC increases as the signaling speed increases. However, certain switches do not enable or disable the FEC mode automatically based on the auto-negotiated transmission speed. This FEC mode must be set manually with the speed while editing the uplink sets. The FEC mode configuration is based on the transceiver and current speed of the port, at connection time.

The interconnect hardware has a default FEC mode value when connected at different speeds. The value from the interconnect hardware may not match the peer device. Different settings can cause a configuration mismatch with the connected source. If the settings are different, the link state will be down.

The following table illustrates possible settings and link state combinations.

When creating uplink ports with 25G and 100G transceivers, FEC must be configured with a clause setting. Each setting represents an algorithm to encode the data stream.

When the FEC is set to Auto, the default clause setting is CL108 for 25G transceivers and CL91 for 100G transceivers. However, both transceivers can be set to CL74.

When the FEC is set to None, the FEC mode is turned off.