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diff --git a/OsmoMSC/chapters/overview.adoc b/OsmoMSC/chapters/overview.adoc new file mode 100644 index 0000000..0bb47d7 --- /dev/null +++ b/OsmoMSC/chapters/overview.adoc @@ -0,0 +1,127 @@ +[[overview]] +== Overview + +This manual should help you getting started with OsmoMSC. It will cover +aspects of configuring and running the OsmoMSC. + +[[intro_overview]] +=== About OsmoMSC + +OsmoMSC is the Osmocom implementation of a Mobile Switching Center (MSC) for 2G +and 3G GSM and UMTS mobile networks. Its interfaces are: + +- GSUP towards OsmoHLR (or a MAP proxy); +- A over IP towards a BSC (e.g. OsmoBSC); +- IuCS towards an RNC or HNB-GW (e.g. OsmoHNBGW) for 3G voice; +- MNCC (Mobile Network Call Control derived from GSM TS 04.07); +- SMPP 3.4 (Short Message Peer-to-Peer); +- The Osmocom typical telnet VTY and CTRL interfaces. + +OsmoMSC originated from the OpenBSC project, which started as a minimalistic +all-in-one implementation of the GSM Network. In 2017, OpenBSC had reached +maturity and diversity (including M3UA SIGTRAN and 3G support in the form of +IuCS and IuPS interfaces) that naturally lead to a separation of the all-in-one +approach to fully independent separate programs as in typical GSM networks. +Before it was split off, OsmoMSC originated from libmsc of the old openbsc.git. +Since a true _A_ interface and IuCS for 3G support is available, OsmoMSC +exists only as a separate standalone entity. + +Key differences of the new OsmoMSC compared to the old OsmoNITB are: + +- The complete VLR implementation that communicates with the separate HLR + (OsmoHLR) for subscriber management. In contrast to the OsmoNITB, HLR queries + are fully asynchronous, and the separate HLR allows using centralized + subscriber management for both circuit-switched and packet-switched domains + (i.e. one OsmoHLR for both OsmoMSC and OsmoSGSN). + +- VLR and HLR brought full UMTS AKA (Authentication and Key Agreement) support, + i.e. Milenage authentication in both the full 3G variant as well as the + backwards compatible 2G variant. + +- Addition of a true _A_ interface for 2G voice services. Previously, OsmoBSC + had an SCCPlite based _A_ interface towards 3rd party MSC implementations. + OsmoMSC features a true SCCP/M3UA _A_ interface, which allows running OsmoBSC + against this Osmocom based MSC implementation. The new SCCP/M3UA SIGTRAN for + the _A_ interface is implemented in libosmo-sccp, which is used by OsmoMSC + and OsmoBSC (and others), to establish a link via an STP (e.g. OsmoSTP). + +- Addition of an _IuCS_ interface to allow operating 3G voice services, also + via SCCP/M3UA SIGTRAN, for example connecting via OsmoHNBGW to a 3G small + cell device. + +Find the OsmoMSC issue tracker and wiki online at + +- https://osmocom.org/projects/osmomsc +- https://osmocom.org/projects/osmomsc/wiki + + +[[fig-gsm]] +.Typical GSM network architecture used with OsmoMSC +[graphviz] +---- +digraph G { + rankdir=LR; + MS0 [label="MS"] + MS1 [label="MS"] + MS2 [label="MS"] + MS3 [label="MS"] + UE0 [label="UE"] + UE1 [label="UE"] + BTS0 [label="BTS"] + BTS1 [label="BTS"] + STP [label="STP\n(SCCP routing)"] + HLR [label="HLR+AUC+EIR"] + HNB [label="RNC or hNodeB"] + MGW + MS0->BTS0 [label="Um"] + MS1->BTS0 [label="Um"] + MS2->BTS1 [label="Um"] + MS3->BTS1 [label="Um"] + UE0->HNB + UE1->HNB + BTS0->BSC [label="Abis"] + BTS1->BSC [label="Abis"] + BSC->STP [label="A/SCCP/M3UA"] + STP->MSC [label="A/SCCP/M3UA"] + STP->MSC [label="IuCS/SCCP/M3UA"] + VLR->HLR [label="GSUP"] + HNB->HNBGW [label="Iuh"] + HNBGW->STP [label="IuCS/SCCP/M3UA"] + MSC->MGW [label="MGCP"] + BTS0->MGW [label="RTP"] + BTS1->MGW [label="RTP"] + subgraph cluster_msc { + label = "OsmoMSC"; + MSC->SMSC; + MSC->VLR + } +} +---- + + +=== Software Components + +This is a brief description of OsmoMSC's internal software components. + +==== SMSC + +A minimal store-and-forward server for SMS, supporting both MO and MT +SMS service, as well as multi-part messages. + +The built-in SMSC also supports an external SMSC interface. For more +information, see <<smpp>>. + +==== MSC + +The MSC component implements the mobility management (MM) functions of the TS +04.08 and delegates to SMSC for SMS message handling and the VLR for subscriber +management. + +Furthermore, it can handle TS 04.08 Call Control (CC), either by use of +an internal MNCC handler, or by use of an external MNCC agent. For more +information see <<mncc>>. + +==== VLR + +A fully featured Visitor Location Register handles the subscriber management +and authentication, and interfaces via GSUP to the external HLR. |