Index allocation

The index allocation attribute is the sequence of index buffers. Each index buffer is 800 bytes (2K). The structure of an index buffer is

    offset(length)         Description
    0(4)                   Magic number 'INDX'
    4(2)                   Offset to fixup (usually 28)
    6(2)                   Number of fixups including first word
    10(8)                  VCN of buffer
    18(2)                  Header size
    1C(4)                  in-use length of buffer
    20(4)                  total length of buffer
    28(A)                  Fixup
    18+header size         Entry list

The entry list is just a sequence of index entries. The fixup works just as it does for MFT records. Because the record size is larger, there are four numbers to check and modify.

What is in the index header, other than the fixup data?