MIB: ENTITY-MIB
The vendor-specific software revision string for the
physical entity.
Note that if revision information is stored internally in a
non-printable (e.g., binary) format, then the agent must
convert such information to a printable format, in an
implementation-specific manner.
If no specific software programs are associated with the
physical component, or if this information is unknown to the
agent, then this object will contain a zero-length string.