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authorHarald Welte <>2018-08-06 22:18:33 +0200
committerHarald Welte <>2018-08-07 18:04:12 +0000
commit128c2db0f6709e2743d2e56e5c8c30c6647020e9 (patch)
parent0c1dad4a5bdb7528f066502b801bb6e31b190a58 (diff)
hlr: Add chapter on USSD configuration
2 files changed, 80 insertions, 0 deletions
diff --git a/OsmoHLR/chapters/ussd.adoc b/OsmoHLR/chapters/ussd.adoc
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+== 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
+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 5678`
+to make it connect to OsmoHLR on IP address and GSUP/TCP port
+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
+This demonstration program will echo back any USSD message sent/routed
+to it, quoted like _You sent "..."_.
diff --git a/OsmoHLR/osmohlr-usermanual.adoc b/OsmoHLR/osmohlr-usermanual.adoc
index 043c971..d9a4654 100644
--- a/OsmoHLR/osmohlr-usermanual.adoc
+++ b/OsmoHLR/osmohlr-usermanual.adoc
@@ -14,6 +14,8 @@ include::chapters/running.adoc[]