User-to-user indicators

           8  7  6  5  4  3  2  1
        1  H  G  F  E  D  C  B  A

        A               Type
0       request
1       response
If bit A equals 0 (request):
        bits
        C B             Service 1
0 0             no information
0 1             spare
1 0             request, not essential
1 1             request, essential
        bits
        E D             Service 2
0 0             no information
0 1             spare
1 0             request, not essential
1 1             request, essential
        bits
        G F             Service 3
0 0             no information
0 1             spare
1 0             request, not essential
1 1             request, essential

        bit
        H               Spare
0
If bit A equals 1 (response):
        bits
        C B             Service 1
0 0             no information
0 1             not provided
1 0             provided
1 1             spare
        bits
        E D             Service 2
0 0             no information
0 1             not provided
1 0             provided
1 1             spare
        bits
        G F             Service 3
0 0             no information
0 1             not provided
1 0             provided
1 1             spare
        bit
        H               Network discard indicator
0               no information
1               user-to-user information discarded by the network