The ifIndex of the FR Major interface. When creating entries in this
table, suitable values for this object are determined by reading already
created FR Major interface values.
Each multilink bundle will be associated with one FR major interface.
This association will be done at the creation of FR major interface
(juniFrDlcmiTable) specifying its lower interfce binding as FR link
ifIndex(juniFrMlFrLinkConfigTable) and the multilink bundle name.