|-7-|-6-|-5-|-4-|-3-|-2-|-1-|-0-|
    |---+---+---+---+---+---+---+---|
 1: | PDU-type      | s | m | a | 0 |
    |---+---+---+---+---+---+---+---|
 2: | 0 | max seg   | max APDU      |
    |---+---+---+---+---+---+---+---|
 3: | invoke id                     |
    |---+---+---+---+---+---+---+---|
 4: | Sequence Number               | only present if SEG = 1
    |---+---+---+---+---+---+---+---|
 5: | Proposed Window Size          | only present if SEG = 1
    |---+---+---+---+---+---+---+---|
 6: | BACNet Confirmed Service Choice |
    |---+---+---+---+---+---+---+---|
 7-n| Service Request               |
    |---+---+---+---+---+---+---+---|