Cellular Network Infrastructure » Core Network (CN) » OsmoMSC

Shall I take this as well? Seems like next logical step to be able to test LCLS with actual hw.

Corresponding libosmocore changes are mostly merged, there're 4 more pending patches for OsmoMSC.
N. B: current implementation is only suitable for testing due to issues with CallRef handling by transactions. This part is going to be heavily changed by intra-BSC handover work.

Experimental implementation available in:
https://gerrit.osmocom.org/c/osmo-msc/+/13421/
https://gerrit.osmocom.org/c/osmo-msc/+/11746/
https://gerrit.osmocom.org/c/osmo-msc/+/13422/
It's already useful enough for testing BSC-side but needs more work to properly handle HO and correctly construct GCR for all interfaces/transaction variants.

assigning to keith, who wanted to have a look at this.

I think there's nothing fundamentally wrong with the three linked patches. There were smaller review issues about coding style, and the fact that the VTY command should not be introdcued first in a separate patch (without any logic). So if they were rebased on top of master, and they can be shown to work with OsmoBSC, they are good to go.

(Things changed so much that it is more like a rewrite than a rebase....)

Some progress:
I have submitted some patchsets to the above gerrit commits, needs clean-up but 'works', - confirmed seeing LCLS params on the SCTP in wireshark* and also received by the BSC

but, noted in the BSC log:

20201115042002382 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: Allocated (fsm.c:461)                                                                                               
20201115042002382 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: is child of SUBSCR_CONN[0x55ff7b75bd20] (fsm.c:491)                                                                 
20201115042005209 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: Received Event UPDATE_CFG_CSC (osmo_bsc_lcls.c:226)                                                                 
20201115042005209 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: LCLS update Config Not available -> Connect both-way (osmo_bsc_lcls.c:180)                                          
20201115042005209 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: LCLS update Control Not available -> Connect (osmo_bsc_lcls.c:188)                                                  
20201115042005911 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: Received Event APPLY_CFG_CSC (osmo_bsc_lcls.c:232)                                                                  
20201115042005911 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: Unsuccessful correlation (osmo_bsc_lcls.c:149)                                                                      
20201115042005911 DLCLS DEBUG LCLS[0x55ff7b7612e0]{NO_LCLS}: state_chg to NOT_POSSIBLE_LS (osmo_bsc_lcls.c:397)        

BSC shows during call:

OsmoBSC# show conns
Active subscriber connections:
conn ID=134, MSC=0, hodec2_fail=0, mgw_ep=rtpbridge/9@mgw
 LCLS GCR: 0362f2240200b9058000000065
 LCLS Config: Connect both-way, LCLS Control: Connect, LCLS BSS Status: NOT_POSSIBLE_LS
BTS 0, TRX 0, Timeslot 1, Lchan 0: Type TCH_H
  Connection: 1, State: ESTABLISHED
  BS Power: 4294967295 dBm, MS Power: 5 dBm
  Channel Mode / Codec: SPEECH_AMR
  Subscriber:
    IMSI: 262420000000333
    Use count: 1 (conn)
  Bound IP: 172.16.0.15 Port 16486 RTP_TYPE2=0 CONN_ID=0
  Conn. IP: 172.16.0.1 Port 4370 RTP_TYPE=98 SPEECH_MODE=0x05
  Measurement Report:
    Flags:
    MS Timing Offset: 0
    L1 MS Power: 5 dBm, Timing Advance: 0
    RXL-FULL-dl:  -84 dBm, RXL-SUB-dl:  -84 dBm RXQ-FULL-dl: 4, RXQ-SUB-dl: 3
    RXL-FULL-ul:  -55 dBm, RXL-SUB-ul:  -55 dBm RXQ-FULL-ul: 0, RXQ-SUB-ul: 0
conn ID=135, MSC=0, hodec2_fail=0, mgw_ep=rtpbridge/b@mgw
 LCLS GCR: 0362f2240200b9050000000065
 LCLS Config: Connect both-way, LCLS Control: Connect, LCLS BSS Status: NOT_POSSIBLE_LS
BTS 0, TRX 0, Timeslot 1, Lchan 1: Type TCH_H
  Connection: 1, State: ESTABLISHED
  BS Power: 4294967295 dBm, MS Power: 5 dBm
  Channel Mode / Codec: SPEECH_AMR
  Subscriber:
    IMSI: 262423203000396
    Use count: 1 (conn)
  Bound IP: 172.16.0.15 Port 16488 RTP_TYPE2=0 CONN_ID=0
  Conn. IP: 172.16.0.1 Port 4378 RTP_TYPE=98 SPEECH_MODE=0x05
  Measurement Report:
    Flags:
    MS Timing Offset: -1
    L1 MS Power: 5 dBm, Timing Advance: 0
    RXL-FULL-dl:  -65 dBm, RXL-SUB-dl:  -65 dBm RXQ-FULL-dl: 0, RXQ-SUB-dl: 0
    RXL-FULL-ul:  -47 dBm, RXL-SUB-ul:  -47 dBm RXQ-FULL-ul: 0, RXQ-SUB-ul: 0
OsmoBSC#

*my wireshark does not decode the GCR

Hmm, the call refs are in fact different.. I did not spot it at a glance.

https://gerrit.osmocom.org/c/osmo-msc/+/13421/
and
https://gerrit.osmocom.org/c/osmo-msc/+/13422/

are now ready for review.

I did not deal with what Max points out in #2487#note-15,

Folowing #2487#note-19, What I have done is to "forward port" and rebase Max's patches with minimal amount of change to the orginal work, opening the way for further improvements, including responding correctly to external MNCC commands from the SIP Agent on the other side of that. The SIP agent has to be able to put itself in and take itself out of the audio path during a call.