The purpose of the Closed user group information element is to indicate the closed user group to be used for that call. It may be used for X.25 packet-mode calls when either an X.25 CUG selection facility or an X.25 CUG with Outgoing Access selection facility is received in an X.25 Incoming Call packet and X.25 and Q.931 mapping applies.
The Closed user group information element is coded as shown in Figure 4-37 and Table 4-27.
The maximum length of this information element is 7 octets.
Bits |
||||||||
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
Closed user group information element identifier |
Octets |
|||||||
0 |
1 |
0 |
0 |
0 |
1 |
1 |
1 |
1 |
Length of information element contents |
2 |
|||||||
1 ext. |
Spare |
CUG indication |
3 |
|||||
0 |
0 |
0 |
0 |
|||||
0 |
CUG index code (IA5) characters) |
4 |
||||||
Closed user group information element
Closed user group information element
CUG indication (octet 3) |
|
Bits |
|
3 2 1 |
|
0 0 1 |
Closed user group selection |
0 1 0 |
Closed user group with outgoing access selection and indication |
All other values are reserved. |
|
CUG index code (octet 4) |
|
Bits |
|
7 6 5 4 3 2 1 |
|
0 1 1 0 0 0 0 |
0 |
0 1 1 0 0 0 1 |
1 |
0 1 1 0 0 1 0 |
2 |
0 1 1 0 0 1 1 |
3 |
0 1 1 0 1 0 0 |
4 |
0 1 1 0 1 0 1 |
5 |
0 1 1 0 1 1 0 |
6 |
0 1 1 0 1 1 1 |
7 |
0 1 1 1 0 0 0 |
8 |
0 1 1 1 0 0 1 |
9 |
All other values are reserved. |
Note - The CUG index code should be represented by up to four IA5 characters, encoded as shown above. |