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diff --git a/OsmoHLR/chapters/ussd.adoc b/OsmoHLR/chapters/ussd.adoc deleted file mode 100644 index be463ac..0000000 --- a/OsmoHLR/chapters/ussd.adoc +++ /dev/null @@ -1,78 +0,0 @@ -[[ussd]] -== Unstructured Supplementary Services Data (USSD) - -The _Unstructured Supplementary Services Data (USSD)_ is one service within -2G/3G networks next to other services such as circuit-switched voice, packet-switched -data and SMS (Short Message Service). - -It is on an abstract level quite similar to SMS in that USSD can be used to send -textual messages. However, there are the following differences: - -* USSD is between the MS (phone) and an USSD application on the network, while - SMS is primarily between two subscribers identified by their MSISDN -* USSD is faster, as it doesn't suffer from the complicated three-layer CP/RP/TP - protocol stack of SMS with it's acknowledgement of the acknowledged acknowledgement. -* USSD is session-oriented, i.e. a dialogue/session between subscriber and application - can persist for the transfer of more than one message. The dedicated radio channel - on the RAN remains established throughout that dialogue. - -=== USSD in Osmocom - -Until August 2018, OsmoMSC contained some minimalistic internal USSD -handling with no -ability to attach/extend it with external USSD applications. - -From August 2018 onwards, OsmoMSC doesn't contain any internal USSD -handlers/applications anymore. Instead, all USSD is transported to/from -OsmoHLR via the GSUP protocol. - -OsmoHLR contains some intenal USSD handlers and can route USSD messages -to any number of external USSD entities (EUSEs). The EUSE also use GSUP -to communicate USSD from/to OsmoHLR. - -Each EUSE is identified by its name. The name consists of a single-word -string preceding a currently fixed ("-00-00-00-00-00-00") suffix. -There is no authentication between EUSE and OsmoHLR: Any client program -able to connect to the GSUP port of OsmoHLR can register as any EUSE -(name). - -NOTE:: We plan to remove the requirement for this suffix as soon as we -are done resolving all more important issues. - -=== USSD Configuration - -USSD configuration in OsmoHLR happens within the `hlr` VTY node. - -`euse foobar-00-00-00-00-00-00` defines an EUSE with the given name `foobar` - -`ussd route prefix *123 external foobar-00-00-00-00-00-00` installs a -prefix route to the named EUSE. All USSD short codes starting with *123 will be -routed to the named EUSE. - -`ussd route prefix *#100# internal own-msisdn` installs a prefix route -to the named internal USSD handler. There above command will restore -the old behavior, in which *#100# will return a text message containing -the subscribers own phone number. There is one other handler called -`own-imsi` which will return the IMSI instead of the MSISDN. - -`ussd default-route external foobar-00-00-00-00-00-00` installs a -default route to the named EUSE. This means that all USSD codes for -which no more specific route exists will be routed to the named EUSE. - -=== Example EUSE program - -We have provided an example EUSE developed in C language using existing -Osmocom libraries for GSUP protocol handling and USSD encoding/decoding. -It will register as `foobar` EUSE to OsmoHLR on localhost. You can run -it on a different machine by specifying e.g. `osmo-euse-demo 1.2.3.4 5678` -to make it connect to OsmoHLR on IP address 1.2.3.4 and GSUP/TCP port -5678. - -The idea is that you can use this as a template to develop your own USSD -applications, or any gateways to other protocols or interfaces. - -You can find it in `osmo-hlr/src/osmo-euse-demo.c` or online by -following the link to http://git.osmocom.org/osmo-hlr/tree/src/osmo-euse-demo.c - -This demonstration program will echo back any USSD message sent/routed -to it, quoted like _You sent "..."_. |