• Table of contents
• WIP
• Osmocom Network In The Box
  • OsmoNITB R.I.P., long live the Network In The Box
  • Part of this Complete Network
• Have to Know
• Configuration Examples
  • OsmoHLR
  • OsmoMSC
  • OsmoMGW
  • OsmoSTP
  • OsmoBSC
  • OsmoHNBGW
  • OsmoGGSN
  • OsmoSGSN
• Running Examples
• Logging Examples

WIP¶

This wiki page is still new and in an alpha state. We're still checking whether it is consistent and contains all the important information.

Osmocom Network In The Box¶

This is a brief guide to the most basic and minimal setup of an Osmocom 2G and/or 3G network for voice and data services. It is a good starting point for newcomers to familiarize with the software, and to expand upon by the Osmocom Manuals and other wiki pages.

OsmoNITB R.I.P., long live the Network In The Box¶

Historically, Osmocom offered the OsmoNITB "Network-In-The-Box" as an actual single program. It was a useful simplification at the time, but in 2017, Osmocom have decided to split OsmoNITB into programs more closely resembling traditional network architecture. It is recommended to use the new separate components instead of the OsmoNITB, since active development focus has moved there.

It is still very much possible to run a complete Osmocom core network in one "box". For example, a sysmoBTS can run the entire core network on the same hardware that drives the TRX, making it a complete network in actually one single box. At the same time, having separate components also allows scaling to large deployments, with properly distributed load and a central subscriber database.

To migrate from OsmoNITB to the new separate programs, see the OsmoNITB Migration Guide.

Part of this Complete Network¶

Assuming that you have your radio hardware ready (a BTS, a femto cell or an SDR driven by osmo-trx), the core network consists of separate programs providing voice/SMS/USSD ("circuit-switched" or CS) and data ("packet-switched" or PS) services.

Here is a table of the components you need:

Required for				Program	Description
2G		3G
CS	PS	CS	PS
✔	✔	✔	✔	OsmoHLR	Home Location Register, stores subscriber IMSI, phone number and auth tokens.
✔	(1)	✔	(1)	OsmoMSC	Mobile Switching Center, handles signalling, i.e. attach/detach of subscribers, call establishment, messaging (SMS and USSD).
✔		✔		OsmoMGW	Media Gateway, is instructed by the MSC and/or the BSC to direct RTP streams for active voice calls.
✔	✔	✔	✔	OsmoSTP	Signal Transfer Point, routes SCCP messages between MSC, BSC, HNBGW and for 3G also the SGSN.
✔	(1)			OsmoBSC	2G Base Station Controller, manages logical channels and other lower level aspects for one or more 2G BTS; it is technically part of the BSS and not the "core network".
		✔	✔	OsmoHNBGW	3G HomeNodeB Gateway, receives the Iuh protocol from a 3G femto cell and forwards to MSC and SGSN by SCCP/M3UA via OsmoSTP.
	✔ (2)		✔ (2)	OsmoGGSN	Gateway GPRS Support Node, "opens" GTP tunnels received from SGSNs to internet uplink.
	✔		✔	OsmoSGSN	Serving GPRS Support Node, handles signalling, i.e. attach/detach of subscribers and PDP contexts.
✔	(1)			OsmoBTS	for 2G networks, drives the TRX and ties to the BSC via Abis-interface.
	✔			OsmoPCU	for 2G networks, a component closely tied to the BTS, drives the TRX for PS timeslots and ties to the SGSN via Gb-interface.

1: PS is always an addition to CS: even though these components do not handle PS requests, you need to have these to be able to setup and register with a network, which is a prerequisite for data services.

2: For the GGSN to successfully route packets to an internet uplink, the system needs to have

• IP-forwarding enabled,
• IP-masquerading set up,
• a usable tunnel device set up.

echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
# Replace 'eth0' with your ethernet device name, or use '*' for all.

Have to Know¶

Each program features a detailed user manual, your primary source of information to expand on the setup described here.

Osmocom offers compiled packages for various distributions. If you're up to it, you may also Build from Source.

Each Osmocom program typically has

• a distinct configuration file;
• a VTY telnet console for live interaction;
• a CTRL interface for live interaction from 3rd party programs.

See Port Numbers to find out which program runs VTY on which port.

Configuration Examples¶

OsmoHLR¶

See the manual on creating a subscriber database, and add one or more subscribers.

While you do need one, your configuration file may actually remain empty. This will serve GSUP on localhost (127.0.0.1), sufficient for a Network In The Box.

OsmoMSC¶

The VLR component of OsmoMSC needs to connect to the OsmoHLR's GSUP server to know which subscribers are authorized. By default, it will connect to OsmoHLR on localhost, no explicit config needed.

To be reachable by OsmoBSC and OsmoHNBGW, OsmoMSC needs an SCCP point code, and it needs to connect to OsmoSTP to make itself known to SCCP routing.

• There is a default point code, currently 0.23.1 (in 8.8.3 point code format).
• OsmoMSC will by default look for OsmoSTP on localhost's M3UA port, 2905.

To direct RTP streams, OsmoMSC needs an OsmoMGW instance. By default, it will look for an MGW on localhost and the default MGCP port, 4222.

Again, your config file may remain empty.

OsmoMGW¶

NOTE: Currently, OsmoMSC still requires the legacy osmo-bsc_mgcp program, which will move to the new osmo-mgw soon. osmo-bsc_mgcp is still available from osmo-mgw.git.

The Media Gateway receives instructions in the form of MGCP messages from OsmoMSC. It forwards RTP streams directly between BTS, femto cells and remote endpoints, e.g. other MGW instances.

Its RTP IP address must be reachable by the BTS / the femto cell.

• In a setup that truly runs in one box (e.g. sysmoBTS or osmo-trx with co-located core network), this may be localhost (127.0.0.1).
• With a separate BTS or RNC (e.g. 3G femto cell or nanoBTS), make sure to configure an IP address that is reachable.

osmo-mgw.cfg

mgcp
  local ip 192.168.0.3
  bind ip 192.168.0.3

The default is to allow any BTS / femto cell IP address to connect.

(Near future: a second OsmoMGW may be needed to run alongside each OsmoBSC instance.)

OsmoSTP¶

OsmoSTP acts as a server for routing messages. OsmoMSC, OsmoBSC, OsmoHNBGW and OsmoSGSN contact OsmoSTP and announce their own point code, after which they may instruct OsmoSTP to route SCCP messages to each other by these point codes.

The basic configuration that permits dynamic routing is:

osmo-stp.cfg

cs7 instance 0
 xua rkm routing-key-allocation dynamic-permitted
 listen m3ua 2905
  accept-asp-connections dynamic-permitted

OsmoBSC¶

OsmoBSC needs to register with OsmoSTP, and contact the MSC by its point code.

OsmoBSC also needs complete configuration of all connected BTS. This example shows configuration for a sysmoBTS.

Furthermore, some network properties need to be set.

The 'gprs mode' determines whether packet switched access will be enabled. 'gprs mode none' switches off data services, as osmo-bts will not contact osmo-pcu to establish data service. This is a configuration without packet switched service:

osmo-bsc.cfg for voice only

network
 network country code 901
 mobile network code 70
 mm info 1
 short name Osmocom
 long name Osmocom
 auth policy closed
 encryption a5 0
 bts 0
  type sysmobts
  band GSM-1800
  cell_identity 0
  location_area_code 23
  ip.access unit_id 1800 0
  gprs mode none
  trx 0
   rf_locked 0
   arfcn 868
   nominal power 23
   timeslot 0
    phys_chan_config CCCH+SDCCH4
   timeslot 1
    phys_chan_config SDCCH8
   timeslot 2
    phys_chan_config TCH/H
   timeslot 3
    phys_chan_config TCH/H
   timeslot 4
    phys_chan_config TCH/H
   timeslot 5
    phys_chan_config TCH/H
   timeslot 6
    phys_chan_config TCH/H
   timeslot 7
    phys_chan_config TCH/H
cs7 instance 0
 ! osmo-bsc's own point code
 point-code 0.42.0
 ! address book entry named 'msc_remote', used below
 sccp-address msc_remote
  point-code 0.23.1
msc 0
 msc-addr msc_remote

To allow data service, set a 'gprs mode gprs' or 'gprs mode egprs', and configure PDCH timeslots. Traditionally, a fixed amount of TCH timeslots for voice and PDCH timeslots for data service are configured. OsmoBTS also supports two types of dynamic timeslots, as described in the Abis manual, chapter "Dynamic Channel Combinations". The following is a configuration with data service based on Osmocom style dynamic timeslots:

osmo-bsc.cfg for voice and data service

network
 network country code 901
 mobile network code 70
 mm info 1
 short name Osmocom
 long name Osmocom
 auth policy closed
 encryption a5 0
 bts 0
  type sysmobts
  band GSM-1800
  cell_identity 0
  location_area_code 23
  ip.access unit_id 1800 0
  gprs mode gprs
  trx 0
   rf_locked 0
   arfcn 868
   nominal power 23
   timeslot 0
    phys_chan_config CCCH+SDCCH4
   timeslot 1
    phys_chan_config SDCCH8
   timeslot 2
    phys_chan_config TCH/F_TCH/H_PDCH
   timeslot 3
    phys_chan_config TCH/F_TCH/H_PDCH
   timeslot 4
    phys_chan_config TCH/F_TCH/H_PDCH
   timeslot 5
    phys_chan_config TCH/F_TCH/H_PDCH
   timeslot 6
    phys_chan_config TCH/F_TCH/H_PDCH
   timeslot 7
    phys_chan_config PDCH
cs7 instance 0
 ! osmo-bsc's own point code
 point-code 0.42.0
 ! address book entry named 'msc_remote', used below
 sccp-address msc_remote
  point-code 0.23.1
msc 0
 msc-addr msc_remote

OsmoHNBGW¶

For connecting a 3G hNodeB (femto cell), OsmoHNBGW is needed to receive Iuh and forward IuCS and IuPS. (For a pure 2G setup, no HNBGW is needed.)

OsmoHNBGW needs to connect to OsmoSTP for routing, and needs to know the MSC and SGSN point codes.

It must also be reachable by the hNodeB, hence its Iuh must typically run on a public IP, not a loopback address like 127.0.0.1.

osmo-hnbgw.cfg

cs7 instance 0
 ! OsmoHNBGW's own local point code
 point-code 0.3.0
 ! Address book entries, used below
 sccp-address msc
  point-code 0.23.1
 sccp-address sgsn
  point-code 0.23.2
hnbgw
 iuh
  local-ip 192.168.0.3
 iucs
  remote-addr msc
 iups
  remote-addr sgsn

OsmoGGSN¶

To provide packet switched service, OsmoGGSN must offer GTP service to the OsmoSGSN. Notably, both OsmoGGSN and OsmoSGSN must use identical port numbers, which an intrinsic requirement of the GTP protocol. Hence they must not run on the same IP address. It is sufficient to, for example, run OsmoGGSN on 127.0.0.2, and OsmoSGSN's GTP on 127.0.0.1.

OsmoGGSN maintains a gsn_restart counter, to be able to reliably communicate to the SGSN that it has restarted. This is kept in the 'state-dir', by default in /tmp.

It also needs access to a tun device. This may be configured ahead of time, so that OsmoGGSN does not need root privileges. If run with 'sudo', OsmoGGSN may also create its own tun device. In below example, the 'tun4' device has been created ahead of time. IPv4 operation is enabled by default, but for future compatibility, it is good to indicate that explicitly.

OsmoGGSN furthermore indicates DNS servers, as well as an IPv4 address range to assign to subscribers' PDP contexts.

osmo-ggsn.cfg

ggsn ggsn0
 gtp bind-ip 127.0.0.2
 apn internet
  tun-device tun4
  type-support v4
  ip dns 0 192.168.100.1
  ip dns 1 8.8.8.8
  ip ifconfig 176.16.222.0/24
  ip prefix dynamic 176.16.222.0/24

OsmoSGSN¶

OsmoSGSN needs to reach the GGSN to establish GTP tunnels for subscribers. It must have a separate GTP IP address from OsmoGGSN, as mentioned before.

For 2G, OsmoSGSN needs to be reachable by the PCU, and needs a public IP for the Gb interface if it is not running directly on the BTS hardware (e.g. on sysmoBTS or when using osmo-trx). For 2G operation, SGSN and GGSN may both use a local IP address for GTP, as long as they differ (e.g. 127.0.0.1 and 127.0.0.2).

For 3G, OsmoSGSN needs to be reachable by both the HNBGW for IuPS as well as by the hNodeB for GTP, i.e. it definitely needs to have a public IP address for the GTP port. IuPS may remain local if both HNBGW and SGSN are on the same box.

Finally, OsmoSGSN needs access to OsmoHLR to access subscriber data. Set 'auth-policy remote' to use the HLR for subscriber authorization. The default

osmo-sgsn.cfg

sgsn
 gtp local-ip 192.168.0.3
 ggsn 0 remote-ip 192.168.0.142
 auth-policy remote
 gsup remote-ip 127.0.0.1

Running Examples¶

Each Osmocom program comes with a systemd service file. It is recommended to place config files in /etc/osmocom/ and launch the individual components using systemd.

When installed from debian or opkg feeds, you will find the systemd service files in /lib/systemd/system/.

Re/starting and stopping then works like this:

systemctl restart osmo-hlr
systemctl stop osmo-hlr

It can be useful to have an osmo-all script to re/start or stop all components at once, edit to pick yours:

osmo-all script

#!/bin/sh
cmd="${1:-start}" 
set -ex
systemctl $cmd osmo-hlr osmo-msc osmo-mgw osmo-ggsn osmo-sgsn osmo-stp osmo-bsc osmo-hnbgw osmo-bts-sysmo osmo-pcu 

which allows

./osmo-all restart
./osmo-all status
./osmo-all stop

For illustration, the manual command invocations for the components would look like this:

osmo-hlr -l hlr.db -c osmo-hlr.cfg
osmo-msc -c osmo-msc.cfg
osmo-mgw -c osmo-mgw.cfg
osmo-ggsn -c osmo-ggsn.cfg
osmo-sgsn -c osmo-sgsn.cfg
osmo-stp -c osmo-stp.cfg
osmo-bsc -c osmo-bsc.cfg
osmo-hnbgw -c osmo-hnbgw.cfg
# on a 2G sysmoBTS:
osmo-bts-sysmo -c osmo-bts.cfg -s -M
osmo-pcu -c osmo-pcu.cfg

Logging Examples¶

Osmocom programs have a common logging mechanism, configurable by the config files as well as the telnet VTY.

Depending on the system's logging configuration, logs may by default be visible in /var/log/daemon.log, or by using journalctl:

journalctl -f -u osmo-hlr

When journalctl is used, it may be necessary to enable it first, e.g. by setting "Storage=volatile" in /etc/systemd/journald.conf followed by a 'systemctl restart systemd-journald'; you may also need to 'systemctl unmask systemd-journald.service systemd-jounald.socket'. Logging will only start appearing for components that were restarted after these changes.

A sure way to see the logs is to connect to the program's telnet VTY and enable logging on the VTY session -- this way you do not modify the application's default logging, but create a separate logging target for your telnet VTY session:

$ telnet localhost 4254
OsmoMSC> logging enable 
OsmoMSC> logging level ?
  all      Global setting for all subsystems
  rll      A-bis Radio Link Layer (RLL)
  cc       Layer3 Call Control (CC)
  mm       Layer3 Mobility Management (MM)
  [...]
OsmoMSC> logging level all ?
everything debug      info       notice     error      fatal      
OsmoMSC> logging level all debug 
OsmoMSC> logging filter all 1

You will see logging output on your telnet console immediately. Note that the VTY prompt is still listening, so you may at any time issue 'logging filter all 0' to switch off logging, and be able to type commands without being cluttered by ongoing log output.