| Neels Hofmeyr | 8c8ebb1 | 2017-09-18 16:19:30 +0200 | [diff] [blame] | 1 | [[overview]] |
| 2 | == Overview |
| 3 | |
| 4 | This manual should help you getting started with OsmoMSC. It will cover |
| 5 | aspects of configuring and running the OsmoMSC. |
| 6 | |
| 7 | [[intro_overview]] |
| 8 | === About OsmoMSC |
| 9 | |
| 10 | OsmoMSC is the Osmocom implementation of a Mobile Switching Center (MSC) for 2G |
| 11 | and 3G GSM and UMTS mobile networks. Its interfaces are: |
| 12 | |
| 13 | - GSUP towards OsmoHLR (or a MAP proxy); |
| 14 | - A over IP towards a BSC (e.g. OsmoBSC); |
| 15 | - IuCS towards an RNC or HNB-GW (e.g. OsmoHNBGW) for 3G voice; |
| 16 | - MNCC (Mobile Network Call Control derived from GSM TS 04.07); |
| 17 | - SMPP 3.4 (Short Message Peer-to-Peer); |
| 18 | - The Osmocom typical telnet VTY and CTRL interfaces. |
| 19 | |
| 20 | OsmoMSC originated from the OpenBSC project, which started as a minimalistic |
| 21 | all-in-one implementation of the GSM Network. In 2017, OpenBSC had reached |
| 22 | maturity and diversity (including M3UA SIGTRAN and 3G support in the form of |
| 23 | IuCS and IuPS interfaces) that naturally lead to a separation of the all-in-one |
| 24 | approach to fully independent separate programs as in typical GSM networks. |
| 25 | Before it was split off, OsmoMSC originated from libmsc of the old openbsc.git. |
| 26 | Since a true _A_ interface and IuCS for 3G support is available, OsmoMSC |
| 27 | exists only as a separate standalone entity. |
| 28 | |
| 29 | Key differences of the new OsmoMSC compared to the old OsmoNITB are: |
| 30 | |
| 31 | - The complete VLR implementation that communicates with the separate HLR |
| 32 | (OsmoHLR) for subscriber management. In contrast to the OsmoNITB, HLR queries |
| 33 | are fully asynchronous, and the separate HLR allows using centralized |
| 34 | subscriber management for both circuit-switched and packet-switched domains |
| 35 | (i.e. one OsmoHLR for both OsmoMSC and OsmoSGSN). |
| 36 | |
| 37 | - VLR and HLR brought full UMTS AKA (Authentication and Key Agreement) support, |
| 38 | i.e. Milenage authentication in both the full 3G variant as well as the |
| 39 | backwards compatible 2G variant. |
| 40 | |
| 41 | - Addition of a true _A_ interface for 2G voice services. Previously, OsmoBSC |
| 42 | had an SCCPlite based _A_ interface towards 3rd party MSC implementations. |
| 43 | OsmoMSC features a true SCCP/M3UA _A_ interface, which allows running OsmoBSC |
| 44 | against this Osmocom based MSC implementation. The new SCCP/M3UA SIGTRAN for |
| 45 | the _A_ interface is implemented in libosmo-sccp, which is used by OsmoMSC |
| 46 | and OsmoBSC (and others), to establish a link via an STP (e.g. OsmoSTP). |
| 47 | |
| 48 | - Addition of an _IuCS_ interface to allow operating 3G voice services, also |
| 49 | via SCCP/M3UA SIGTRAN, for example connecting via OsmoHNBGW to a 3G small |
| 50 | cell device. |
| 51 | |
| 52 | Find the OsmoMSC issue tracker and wiki online at |
| 53 | |
| 54 | - https://osmocom.org/projects/osmomsc |
| 55 | - https://osmocom.org/projects/osmomsc/wiki |
| 56 | |
| 57 | |
| 58 | [[fig-gsm]] |
| 59 | .Typical GSM network architecture used with OsmoMSC |
| 60 | [graphviz] |
| 61 | ---- |
| 62 | digraph G { |
| 63 | rankdir=LR; |
| 64 | MS0 [label="MS"] |
| 65 | MS1 [label="MS"] |
| 66 | MS2 [label="MS"] |
| 67 | MS3 [label="MS"] |
| 68 | UE0 [label="UE"] |
| 69 | UE1 [label="UE"] |
| 70 | BTS0 [label="BTS"] |
| 71 | BTS1 [label="BTS"] |
| 72 | STP [label="STP\n(SCCP routing)"] |
| 73 | HLR [label="HLR+AUC+EIR"] |
| 74 | HNB [label="RNC or hNodeB"] |
| 75 | MGW |
| 76 | MS0->BTS0 [label="Um"] |
| 77 | MS1->BTS0 [label="Um"] |
| 78 | MS2->BTS1 [label="Um"] |
| 79 | MS3->BTS1 [label="Um"] |
| 80 | UE0->HNB |
| 81 | UE1->HNB |
| 82 | BTS0->BSC [label="Abis"] |
| 83 | BTS1->BSC [label="Abis"] |
| 84 | BSC->STP [label="A/SCCP/M3UA"] |
| 85 | STP->MSC [label="A/SCCP/M3UA"] |
| 86 | STP->MSC [label="IuCS/SCCP/M3UA"] |
| 87 | VLR->HLR [label="GSUP"] |
| 88 | HNB->HNBGW [label="Iuh"] |
| 89 | HNBGW->STP [label="IuCS/SCCP/M3UA"] |
| 90 | MSC->MGW [label="MGCP"] |
| 91 | BTS0->MGW [label="RTP"] |
| 92 | BTS1->MGW [label="RTP"] |
| 93 | subgraph cluster_msc { |
| 94 | label = "OsmoMSC"; |
| 95 | MSC->SMSC; |
| 96 | MSC->VLR |
| 97 | } |
| 98 | } |
| 99 | ---- |
| 100 | |
| 101 | |
| 102 | === Software Components |
| 103 | |
| 104 | This is a brief description of OsmoMSC's internal software components. |
| 105 | |
| 106 | ==== SMSC |
| 107 | |
| 108 | A minimal store-and-forward server for SMS, supporting both MO and MT |
| 109 | SMS service, as well as multi-part messages. |
| 110 | |
| 111 | The built-in SMSC also supports an external SMSC interface. For more |
| 112 | information, see <<smpp>>. |
| 113 | |
| 114 | ==== MSC |
| 115 | |
| 116 | The MSC component implements the mobility management (MM) functions of the TS |
| 117 | 04.08 and delegates to SMSC for SMS message handling and the VLR for subscriber |
| 118 | management. |
| 119 | |
| 120 | Furthermore, it can handle TS 04.08 Call Control (CC), either by use of |
| 121 | an internal MNCC handler, or by use of an external MNCC agent. For more |
| 122 | information see <<mncc>>. |
| 123 | |
| 124 | ==== VLR |
| 125 | |
| 126 | A fully featured Visitor Location Register handles the subscriber management |
| 127 | and authentication, and interfaces via GSUP to the external HLR. |