This attribute indicates the required minimum level of security of
the trunks on the route. Zero(0) represents the most secure and
seven(7) represents the least secure. The trunk's security is
indicated by the trunkSecurity attribute of the Trunk component,
and has values identical in range and meaning to the
requiredSecurity attribute. PORS ensures that any route selected
does not contain a trunk whose trunkSecurity attribute is
numerically greater than the requiredSecurity.