| Attribute | Must | Description |
|---|---|---|
| X25-Call-User-Data-Incoming | Given by the public carrier. Example: 313 0101 | |
| X25-Call-User-Data-Outgoing | Given by the public carrier. Example: 313 0101 | |
| X25-Facilities-Data-Incoming | Specifies which facilities the switch will support e.g. window size negoiation | |
| X25-Facilities-Data-Outgoing | Specifies which facilities the switch will support e.g. window size negoiation | |
| X25-Remote-MTA-Phone | Phone number of the remote X.400 MTA |