This OID reports the actual, currently negotiated PCI Express link width, in lanes, for this device function, returning 0 if it could not be determined or the device is not PCIe. An admin troubleshooting reduced throughput on a PCIe card compares this negotiated lane count against the card's and slot's maximum supported width to see if the link only trained up to a narrower width than expected. For example, a card designed for 8 lanes but reporting a negotiated link width of 4 here would indicate it is only running at half its intended lane count, likely due to a slot or riser limitation.