OSMO HnbGW , problems with SCTP towards real MSC and SGSN - OpenBSC

25 Mar 2022

Hi,

I'm getting closer. But SCTP does not come up, both my real MSC and SGSN sends SCTP
ABORT:

283 2022-03-25 08:14:08.200734109 10.30.50.124 -> 10.40.33.6   SCTP 86 INIT
284 2022-03-25 08:14:08.201189770   10.40.33.6 -> 10.30.50.124 SCTP 298 INIT_ACK
285 2022-03-25 08:14:08.201286756 10.30.50.100 -> 10.40.2.66   SCTP 86 INIT
286 2022-03-25 08:14:08.201405921   10.40.2.66 -> 10.30.50.100 SCTP 60 ABORT
287 2022-03-25 08:14:08.204033135 10.30.50.124 -> 10.40.33.6   SCTP 254 COOKIE_ECHO
288 2022-03-25 08:14:08.204405432   10.40.33.7 -> 10.30.50.124 SCTP 130 HEARTBEAT
289 2022-03-25 08:14:08.204423695   10.40.33.6 -> 10.30.50.124 SCTP 64 COOKIE_ACK
290 2022-03-25 08:14:08.204595511   10.40.33.6 -> 10.30.50.124 SCTP 64 ABORT
291 2022-03-25 08:14:08.207135400 10.30.50.124 -> 10.40.33.7   SCTP 60 ABORT

SCTP endpoints:

SGSN                    HnbGw                   MSC
-------------------------------------------------------------------------------
10.40.33.6| <---------> 10.30.40.124            |10.40.2.66
10.40.33.7|             10.30.40.100 <--------->        |10.40.2.74

I suspect the source port on HnbGw:

    Source: 10.30.50.100
    Destination: 10.40.2.66
Stream Control Transmission Protocol, Src Port: 38989 (38989), Dst Port: 2905 (2905)
    Source port: 38989
    Destination port: 2905

The MSC sends ABORT as answer to SCTP-INIT. But our SGSN seems to accept INIT and COOKIE,
but eventually sends ABORT.
OsmoHNBGW> show version
OsmoHNBGW 1.2.1 (OsmoHNBGW).

So a few questions:
- I tried to set local port to 2905 under asp in config file, but was rejected ( no such
command ). So is there a way to set source port ?
- In MSC and SGSN we must give local and remote port for the SCTP link. Have you tested
HnbGW with real Ericsson MSC and SGSN ?
- There are many parameters and timers connected to SCTP protocol:

                HBInterval                3;
                MaxAssociationRetransmits 10;
                MaxInitRetransmits        3;
                MaxPathRetransmits        5;
                RTOInitial                3000;
                RTOMax                    6000;
                RTOMin                    1000;
                ValCookieLife             60000;

Are these hardcoded, or could they be configured ?

Thanks,

/Sjur

Internal