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1) Expand the Abstract to be more specific about the proposed mechanism.
2) Rename the 'MBZ' part to 'Reserved' in Boot-request-v6 flags format. This is because the rest bits are reserved for future use. If using 'MBZ' is a common practice, we can change it back.
3) Simplify the section  of 'Use of the Boot-request-v6 Unicast Flag' and give an informative reference to RFC5010.
4) In the section of 'Client Behavior', replace the description of setting the Unicast flag to a pointer to section 7 ('Use of the Boot-request-v6 Unicast Flag').