reserved field [EtherGuide Glossary]

In an MPEG-2 private table section and MPEG-2 descriptors, when a reserved field is encountered, the user or implementer has no ability to use the field until or if the reservation is removed in a later edition of the particular specification. In the meantime, unless specificall noted otherwise, reserved fields in table sections must be "set" to '1' bits.

Glossary