Description: The vendor-specific serial number string for the physical entity. The preferred value is the serial number string actually printed on the component itself (if present).

On the first instantiation of a physical entity, the value of docsRphyRpdIfPhysEntitySerialNum associated with that entity is set to the correct vendor-assigned serial number, if this information is available to the agent. If a serial number is unknown or non-existent, the docsRphyRpdIfPhysEntitySerialNum will be set to a zero-length string instead.

Note that implementations that can correctly identify the serial numbers of all installed physical entities do not need to provide write access to the docsRphyRpdIfPhysEntitySerialNum object. Agents that cannot provide non-volatile storage for the docsRphyRpdIfPhysEntitySerialNum strings are not required to implement write access for this object.

Not every physical component will have a serial number, or even need one. Physical entities for which the associated value of the docsRphyRpdIfPhysEntityIsFRU object is equal to 'false(2)' (e.g., the repeater ports within a repeater module) do not need their own unique serial numbers. An agent does not have to provide write access for such entities and may return a zero-length string.