A message sent in the forward direction to initiate seizure of an outgoing circuit and to transmit number and other information relating to the routing and handling of a call.
| Parameter | Type | Length (octets) |
|---|---|---|
| Message type | F | 1 |
| Nature of connection indicators | F | 1 |
| Forward call indicators | F | 2 |
| Calling party's category | F | 1 |
| Transmission medium requirement | F | 1 |
| Called party number | V | 4-? |
| Transit network selection (national use) | O | 4-? |
| Call reference (national use) | O | 7 |
| Calling party number (Note 2) | O | 4-? |
| Optional forward call indicators | O | 3 |
| Redirecting number (Note 2) | O | 4-? |
| Redirection information | O | 3-4 |
| Closed user group interlock code | O | 6 |
| Connection request | O | 7-9 |
| Original called number (Note 2) | O | 4-? |
| User-to-user information | O | 3-131 |
| Access transport | O | 3-? |
| User service information | O | 4-13 |
| User-to-user indicators | O | 3 |
| Generic number (Notes 1 and 2) | O | 5-? |
| Propagation delay counter | O | 4 |
| User service information prime | O | 4-13 |
| Network specific facility (national use) | O | 4-? |
| Generic digit (national use) (Note 1) | O | 4-? |
| Origination ISC point code | O | 4 |
| User teleservice information | O | 4-5 |
| Remote operations (national use) | O | 8-? |
| Parameter compatibility information | O | 4-? |
| Generic notification indicator (Note 1) | O | 3 |
| Service activation | O | 3-? |
| Generic reference (reserved ) | O | 5-? |
| MLPP precedence | O | 8 |
| Transmission medium requirement prime | O | 3 |
| Location number (Note 2) | O | 4-? |
| Forward GVNS | O | 5-26 |
| CCSS | O | 3-? |
| Network management controls | O | 3-? |
| Circuit assignment map | O | 6-7 |
| Correlation id | O | 3-? |
| Call diversion treatment indicators | O | 3-? |
| Called IN number (Note 2) | O | 4-? |
| Call offering treatment indicators | O | 3-? |
| Conference treatment indicators | O | 3-? |
| SCF id | O | 3-? |
| UID capability indicators | O | 3-? |
| Echo control information | O | 3 |
| Hop counter | O | 3 |
| Collect call request | O | 3 |
| End of optional parameters | O | 1 |
NOTE 1 - This parameter may be repeated. NOTE 2 - Peer-to-peer interworking with an earlier version of ISUP may result in format errors and lead to the release of the call.