| Philipp Maier | 1759ed5 | 2023-10-23 17:05:27 +0200 | [diff] [blame] | 1 | [[sgs]] |
| 2 | == SGs interface |
| 3 | |
| 4 | OsmoMSC offers an SGs interface using the SGsAP protocol. The SGs interface is an |
| 5 | optional interface between a 2G (GERAN) / 3G (UTRAN) MSC and an 4G (EUTRAN) MME. |
| 6 | Its purpose is to facilitate both CSFB (Circuit-Switched Fall Back) and SMSoS |
| 7 | (SMS over SGs). It is used for Mobility management (MM) and paging procedures |
| 8 | between the EPS (Evolved Packet Services) and CS (Circuit Switched) domain. |
| 9 | |
| 10 | === VTY configuration |
| 11 | |
| 12 | The SGs interface implementation in OsmoMSC is automatically active and requires |
| 13 | only minimal configuration. When no specific configuration is provided OsmoMSC |
| 14 | will listen on 0.0.0.0:29118 (SCTP) for incoming connections. |
| 15 | |
| 16 | This is sufficient in the most configurations, but in larger installations, |
| 17 | where services are either tied to specific interfaces and/or more instances of |
| 18 | OsmoMSC run in parallel, a custom configuration is necessary. |
| 19 | |
| 20 | The user has the option to configure the IP address (`local-ip`) and the SCTP |
| 21 | port (`local-port`) and also the `vlr-name` that OsmoMSC uses to identify itself |
| 22 | towards the MME. It should be noted that the `vlr-name` is usually the DNS name |
| 23 | for the IP address of the VLR/MSC, so IP address used and the `vlr-name` should |
| 24 | match the DNS server entry. |
| 25 | |
| 26 | ---- |
| 27 | sgs |
| 28 | local-ip 127.0.0.1 |
| 29 | local-port 29118 |
| 30 | vlr-name vlr.example.net |
| 31 | ---- |
| 32 | |
| 33 | In order to fine tune the behavior of the SGs interface the user also has |
| 34 | control over the relevant timers (`ts5`, `ts6-2`, `ts7`, `ts11`, `ts14`, `ts15`) |
| 35 | and counters (`ns7`, `ns11`). Each timer and counter has to be configured |
| 36 | separately. In the following example we change the value of ts and ns11. |
| 37 | |
| 38 | ---- |
| 39 | sgs |
| 40 | timer ts7 23 |
| 41 | counter ns11 100 |
| 42 | ---- |
| 43 | |
| 44 | |
| 45 | [NOTE] |
| 46 | ==== |
| 47 | In case multiple instances of OsmoMSC run in parallel, it is advised to use a |
| 48 | different `vlr-name` for each instance. In any case it must be ensured that the |
| 49 | SGs interface of each instance is bound to a different IP address and/or port. |
| 50 | ==== |
| 51 | |
| 52 | === Connection monitoring |
| 53 | |
| 54 | The user can use the VTY command `show sgs-connections` to list the MMEs that |
| 55 | are currently connected to OsmoMSC. |