The purpose of the User-user information element is to convey information between ISDN users. This information is not interpreted by the network, but rather is carried transparently and delivered to the remote user(s).
The User-user information element is coded as shown in Figure 4-36 and Table 4-26. There are no restrictions on content of the user information field.
In SETUP, ALERTING, CONNECT, DISCONNECT,RELEASE and RELEASE COMPLETE messages, the User-user information element has a network dependent maximum size of 35 or 131 octets. The evolution to a single maximum value is the long term objective; the exact maximum value is the subject of further study.
In USER INFORMATION messages sent in association with a circuit-mode connection, the User-user information element has a network dependent maximum size of 35 or 131 octets. For USER INFORMATION messages sent in a temporary or permanent user-user signalling connection, the user information field contained inside this information element has a maximum size equal to the maximum size of messages defined in clause 3, that is 260 octets.
Note - The User-user information element is transported transparently by an ISDN between a call originating entity,e.g. a calling user and the addressed entity, e.g. a remote user or a high layer function network node addressed by the call originating entity.
Bits |
||||||||
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Octets |
User-user Information element identifier |
||||||||
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
1 |
Length of user-user contents |
2 |
|||||||
Protocol discriminator |
3 |
|||||||
User information |
4 |
|||||||
User-user information element
User-user information element
Protocol discriminator (octet 3) |
|
Bits |
|
8 7 6 5 4 3 2 1 |
|
0 0 0 0 0 0 0 0 |
User-specific protocol (Note 1) |
0 0 0 0 0 0 0 1 |
OSI high layer protocols |
0 0 0 0 0 0 1 0 |
X.244 [44] (Note 2) |
0 0 0 0 0 0 1 1 |
Reserved for system management convergence function |
0 0 0 0 0 1 0 0 |
IA5 characters (Note 4) |
0 0 0 0 0 1 0 1 |
X.208 and X.209 coded user information (Note 5) |
0 0 0 0 0 1 1 1 |
Rec. V.120 [9] rate adaption |
0 0 0 0 1 0 0 0 |
Q.931/I.451 user-network call control messages |
0 0 0 1 0 0 0 0 |
Reserved for other network layer or layer 3 protocols, Including Recommendation X.25 [5] (Note 3) |
0 1 0 0 0 0 0 0 |
National use. |
0 1 0 1 0 0 0 0 |
Reserved for other network layer or layer 3 Protocols, including Recommendation X.25 (Note 3) |
All other values are reserved. |
|
NOTES 1. The user information is structured according to user needs. 2. The user information is structured according to Recommendation X.244 which specifies the structure of X.25 call user data. 3. These values are reserved to discriminate these protocol discriminators from the first octet of a Recommendation X.25 packet including general format identifier. 4. The user information consists of IA5 characters. 5. The number of X.208 and X.209 components contained in a User-user information element as well as their semantics and use are user-application dependent and may be subject to other Recommendations. |
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