> RFC 2119, section 6: ``Imperatives of the type defined in this memo > must be used with care and sparingly. In particular, they MUST only > be used where it is actually required for interoperation or to limit > behavior which has potential for causing harm (e.g., limiting > retransmisssions) For example, they must not be used to try to impose > a particular method on implementors where the method is not required > for interoperability.'' fwiw, this only applies to documents that cite RFC 2119 for definitions of those terms. other documents have used other definitions.