Move osmo-bsc (with osmo-bts-trx and osmo-trx-lms) to another device

historical

On Fri, Aug 17, 2018 at 09:47:01AM +0000, Norbertas Kremeris wrote:
> Dear all,
> 
> I have a running and working osmocom network stack (2g only, no 
> GPRS/DATA) with osmo-trx-lms using a LimeSDR mini (osmo-trx-lms, 
> osmo-bts-trx, osmo-bsc, osmo-hlr, osmo-stp, osmo-msc, a and single 
> osmo-mgw process) , and I would like to have osmo-bts-trx, osmo-trx-lms 
> and osmo-bsc moved to another computer. I would like to have an AoIP 
> connection between the pc1 and pc2. As far as i understand, osmo-bsc and 
> osmo-mgw communicate over AoIP (as per the manual here 
> http://ftp.osmocom.org/docs/latest/osmomgw-usermanual.pdf).

osmo-mgw, the media gateway, has no AoIP connection. It receives MGCP from BSC
and/or MSC, and directs RTP between BTS and remote peers.

AoIP connects osmo-bsc to osmo-MSC. In detail, AoIP is an SCCP/M3UA connection,
which is routed via an osmo-stp.

Take a look at
http://osmocom.org/projects/cellular-infrastructure/wiki/Osmocom_Network_In_The_Box#Topology

> My knowledge about the interconnection of all the osmocom core 
> components is rather limited, and what at first seemed like a trivial 
> task (to move osmo-bsc to the other computer and changing the msc mgw 
> remote ip) has turned into a 2 day ordeal with me trying to wrap my head 
> around the functionality of all the core components without any success.

Sorry to hear that, but it is rather complex, and has to be since we are trying
to be as 3GPP compliant as possible, to remain interoperable with 3rd party
components.

My "personal pitfalls" are choosing the right IP addresses for the programs to
listen on, so that they are reachable by the intended peers; and configuring
the SCCP links between BSC via STP to MSC, i.e. the 'cs7' instance config.

Once these are figured out, things shouldn't be too hard to get working,
especially since your network already worked before.

> I have modified my stack to work with a single osmo-mgw process (but the 
> moving of osmo-bsc does not work with osmo-mgw-for-bsc and 
> osmo-mgw-for-msc either). Attached are all the configuration files used. 
> The IP of the osmo-bts-trx, osmo-trx-lms and osmo-bsc running pc (PC1) 
> is 192.168.1.249, the ip of the pc (PC2) that is running the core 
> network components is 192.168.1.219. All my osmocom components are built 
> from source (latest tags).
> 
> Running the osmoBSC on the PC1 connects to osmo-bts successfully and 
> does result in a network being shown on the phone, but osmo-bsc 
> constantly throws errors:
> 
>          <0007> a_reset.c:106 A-RESET(msc-0)[0x1ee0530]{DISC}: 
> (re)sending BSSMAP RESET message...
>          <0007> osmo_bsc_sigtran.c:92 Sending RESET to MSC: 
> RI=SSN_PC,PC=0.23.1,SSN=BSSAP
>          <001c> m3ua.c:507 XUA_AS(as-clnt-msc-0)[0x1edfd30]{AS_DOWN}: 
> Event AS-TRANSFER.req not permitted
> 
> Any pointers would be very appreciated.

Apparently the 'cs7' config is wrong.

Looking at your PC1/osmo-bsc.cfg, you don't have a 'cs7' config at all. The
AoIP defaults only work when all components run on the same machine.

The 'msc' config at the bottom of the file is related to the legacy osmo-bsc
SCCPlite connection and does not affect the AoIP connection.

So, you need to tell the SS7 stack (a.k.a. 'cs7 instance') at least the STP's
IP address.

Trying to point you at it, I notice that the osmo-bsc manual lacks this
information :/   (opened https://osmocom.org/issues/3476 )

The OsmoMSC manual has this information, and it is mostly identical between
osmo-bsc and osmo-msc; see
http://ftp.osmocom.org/docs/latest/osmomsc-usermanual.pdf 
section 'Running OsmoMSC' / 'Configure primary links' / 'Configure SCCP/M3UA to
accept A and IuCS links'

(Easiest is to use the default point-codes; otherwise osmo-bsc.cfg also needs
an address book entry under 'cs7', and pass this name to 'msc 0' / 'msc-addr'.
point codes are logged on startup).

You can also view the default cs7 instance config: start up your current
osmo-bsc, connect via telnet vty:
  telnet localhost 4242
and do

  OsmoBSC> enable
  OsmoBSC# show running-config

then look for the 'cs7 instance' section.

I think osmo-stp by default listens on all interfaces, otherwise you also need
to tell the osmo-stp.cfg to listen on a public IP address.

  cs7 instance 0
   listen m3ua 2905
    local-ip 123.45.67.8

Hope that helps!

I think this information needs a wiki page...
(opened https://osmocom.org/issues/3477 )

~N
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