> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/parameter-reference/sub-system-number.md).

# Sub-System Number

The Sub-System Number parameter is used to assign a sub-system number to an object within the SS7 SCCP control layer.

Integer values for this parameter are entered into a field.

Allowable values are from 1 to 255.

| SSN value | SSN SCCP user      | Description                                               |
| --------- | ------------------ | --------------------------------------------------------- |
| 0         | Unknown            | SSN not known or not used.                                |
| 1         | SCCP management    | SCCP management                                           |
| 3         | ISUP               | ISDN user part                                            |
| 4         | OMAP               | Operation, Maintenance and Administration Part            |
| 5         | MAP                | Mobile Application Part                                   |
| 6         | HLR                | Home Location Register (MAP)                              |
| 7         | VLR                | Visitor Location Register (MAP)                           |
| 8         | MSC                | Mobile Switching Center (MAP)                             |
| 9         | EIR                | Equipment Identifier Register (MAP)                       |
| 10        | AUC                | Authentication Center                                     |
| 11        | ISDN supplementary | ISDN Supplementary services                               |
| 13        | BISDNE2EAPP        | Broadband ISDN Edge-to-Edge Application                   |
| 14        | TCTR               | TC Test Responder                                         |
| 142       | RANAP              | Radio Access Network Application Part                     |
| 143       | RNSAP              | Radio Network Subsystem Application Part                  |
| 145       | GMLC               | Gateway Mobile Location Centre (MAP)                      |
| 146       | CAP                | CAMEL application part                                    |
| 147       | gsmSCF             | Global System for Mobile Service Control Function (MAP)   |
| 148       | SIWF               | Serving GPRS Support Node (MAP)                           |
| 149       | SGSN               | Serving GPRS Support Node (MAP)                           |
| 150       | GGSN               | Gateway GPRS Support Node (MAP)                           |
| 249       | PCAP               | Positioning Calculation Application Part                  |
| 250       | BSC BSSAP          | BSC Base Station System Application Part (BSSAP-LE)       |
| 251       | MSC BSSAP          | MSC Base Station System Application Part (BSSAP-LE)       |
| 252       | SMLC BSSAP         | Serving Mobile Location Center (BSSAP-LE)                 |
| 253       | BSSOM              | Base Station System Operation & Maintenance (A-interface) |
| 254       | BSSAP              | Base Station System Application Part (A-interface)        |


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