SDCCH not released if Radio Link Failure / Sending Connection Failure: cause = 0x001 Experienced in osmo-bsc and osmo-bts-trx

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Ron ron.menez at entropysolution.com
Sat Aug 4 04:29:40 UTC 2018 

Hi Community,

We had encountered an issue regarding the SDCCH channel not being released immediately after a "Radio Link Failure" is detected in osmo-bsc and an equivalent error of "Sending Connection Failure: cause = 0x01" in osmo-bts-trx.

Error in osmo-bts-trx:
<0000> rsl.c:797 (bts=0,trx=0,ts=0,ss=0) Sending Connection Failure: cause = 0x01

Error in osmo-bsc:
<0003> abis_rsl.c:1372 (bts=0,trx=0,ts=0,ss=0) CONNECTION FAIL in state ACTIVE CAUSE=0x01(Radio Link Failure)

With this issue, the SDCCH channel will then be exhausted and no other subscriber can attach and do any services (call and SMS).

As per advised by Neels, we tried to used the neels/inter_bsc_ho branch for osmo-bsc to test if this issue is fixed.

We are happy to inform the community that the SDCCH channel issue we had is not experienced from the neels/inter_bsc_ho branch but a different bug was experienced.

The bug we seen in this branch is that, even we have a 2 TRX configuration in our setup, the osmo-bsc only uses the first TRX configuration. Kindly see logs below for your reference.

OSMO-BSC:

# /usr/local/osmo-bsc/src/osmo-bsc/osmo-bsc -c /root/demo/osmo-bsc.cfg
logging level cc (everything|debug|info|notice|error|fatal)
logging level mgcp (everything|debug|info|notice|error|fatal)
<001f> osmo_ss7.c:1270 0: ASP Restart for server not implemented yet!
% Ignoring deprecated logging level everything
<0013> telnet_interface.c:104 telnet at 127.0.0.1 4242
<0015> input/ipaccess.c:846 enabling ipaccess BSC mode on 0.0.0.0 with OML 3002 and RSL 3003 TCP ports
<001a> control_if.c:887 CTRL at 127.0.0.1 4249
<0007> osmo_bsc_sigtran.c:466 Initializing SCCP connection to MSC msc-0
<0007> osmo_bsc_sigtran.c:476 CS7 Instance identifier, A-Interface: 0
<0020> sccp_user.c:397 msc-0: Using SS7 instance 0, pc:0.23.3
<0020> sccp_user.c:421 msc-0: Using AS instance MSC_Test
<0020> sccp_user.c:426 msc-0: Creating default route
<0020> sccp_user.c:481 msc-0: Using ASP instance Huawei_MSC_Test
<0020> sccp_user.c:484 msc-0: Creating SCCP instance
<0007> osmo_bsc_sigtran.c:519 (msc-0) A-interface: local (BSC) SCCP address: RI=SSN_PC,PC=0.23.3,SSN=BSSAP
<0007> osmo_bsc_sigtran.c:521 (msc-0) A-interface: remote (MSC) SCCP address: RI=SSN_PC,PC=0.23.1,SSN=BSSAP
<0007> a_reset.c:106 A-RESET(msc-0)[0xce7480]{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
<001f> m3ua.c:507 XUA_AS(MSC_Test)[0xcdb9d0]{AS_DOWN}: Event AS-TRANSFER.req not permitted
<0007> a_reset.c:106 A-RESET(msc-0)[0xce7480]{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
<001f> m3ua.c:507 XUA_AS(MSC_Test)[0xcdb9d0]{AS_DOWN}: Event AS-TRANSFER.req not permitted
<0007> a_reset.c:106 A-RESET(msc-0)[0xce7480]{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
<001f> m3ua.c:507 XUA_AS(MSC_Test)[0xcdb9d0]{AS_INACTIVE}: Event AS-TRANSFER.req not permitted
<0022> m3ua.c:634 asp-Huawei_MSC_Test: Received NOTIFY Type State Change:AS Inactive ()
<001f> xua_default_lm_fsm.c:353 xua_default_lm(Huawei_MSC_Test)[0xce6de0]{ACTIVE}: Ignoring primitive M-ASP_ACTIVE.confirm
<0022> m3ua.c:634 asp-Huawei_MSC_Test: Received NOTIFY Type State Change:AS Active ()
<0007> a_reset.c:106 A-RESET(msc-0)[0xce7480]{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
<0007> osmo_bsc_bssap.c:58 RESET ACK from MSC: RI=SSN_PC,PC=0.23.1,SSN=BSSAP
<0007> a_reset.c:74 A-RESET(msc-0)[0xce7480]{DISC}: SIGTRAN connection succeded.
<0015> input/ipa.c:265 accept()ed new link from 192.168.1.170 to port 3002
<0004> abis_nm.c:499 BTS0 feature 'EGPRS' reported via OML does not match statically set feature: 0 != 1. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'OML Alerts' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'Fullrate speech V1' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'Halfrate speech V1' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'Fullrate speech EFR' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'Fullrate speech AMR' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:499 BTS0 feature 'Halfrate speech AMR' reported via OML does not match statically set feature: 1 != 0. Please fix.
<0004> abis_nm.c:566 OC=BTS(01) INST=(00,ff,ff): BTS0: ARI reported sw[0/2]: osmobts is 0.8.1.35-6575f0
<0004> abis_nm.c:438 BTS0 reported variant: omso-bts-trx
<0004> abis_nm.c:460 BTS0 Attribute Manufacturer Dependent State is unreported
<0004> abis_nm.c:566 OC=BTS(01) INST=(00,ff,ff): BTS0: ARI reported sw[0/1]: TRX_PHY_VERSION is Unknown
<0004> abis_nm.c:460 BTS0 Attribute Manufacturer Dependent State is unreported
<0004> abis_nm.c:566 OC=BTS(01) INST=(00,ff,ff): BTS0: ARI reported sw[0/1]: TRX_PHY_VERSION is Unknown
<0004> abis_nm.c:2827 IPA RSL CONNECT IP=0.0.0.0 PORT=3003 STREAM=0x00
<0004> abis_nm.c:2827 IPA RSL CONNECT IP=0.0.0.0 PORT=3003 STREAM=0x00
<0015> input/ipa.c:265 accept()ed new link from 192.168.1.170 to port 3003
<0003> osmo_bsc_main.c:282 bootstrapping RSL for BTS/TRX (0/0) on ARFCN 111 using MCC-MNC 101-01 LAC=20259 CID=6966 BSIC=63
<0015> input/ipa.c:265 accept()ed new link from 192.168.1.170 to port 3003
<0003> osmo_bsc_main.c:282 bootstrapping RSL for BTS/TRX (0/1) on ARFCN 13 using MCC-MNC 101-01 LAC=20259 CID=6966 BSIC=63
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-0-CCCH_SDCCH4)[0xce0220]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-1-SDCCH8)[0xce0650]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-2-TCH_F)[0xce0c00]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-3-TCH_F)[0xce11b0]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-4-TCH_F)[0xce1760]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-5-TCH_F)[0xce1d10]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-6-TCH_F)[0xce22c0]{UNUSED}: Event TS_EV_OML_READY not permitted
<0011> bts_ipaccess_nanobts.c:314 timeslot(0-0-7-TCH_F)[0xce2870]{UNUSED}: Event TS_EV_OML_READY not permitted

<0003> abis_rsl.c:1364 (bts=0) CHAN RQD: reason: other (ra=0xfe, neci=0x00, chreq_reason=0x04)
<0010> lchan_fsm.c:76 lchan(0-0-0-CCCH_SDCCH4-0)[0xce7f70]{WAIT_RLL_RTP_ESTABLISH}: (type=SDCCH) lchan allocation failed in state WAIT_RLL_RTP_ESTABLISH: Timeout
<0010> lchan_fsm.c:95 lchan(0-0-0-CCCH_SDCCH4-0)[0xce7f70]{WAIT_RLL_RTP_ESTABLISH}: (type=SDCCH) Tx Immediate Assignment Reject (lchan allocation failed in state WAIT_RLL_RTP_ESTABLISH: Timeout)
<0003> abis_rsl.c:1364 (bts=0) CHAN RQD: reason: Location updating (ra=0x09, neci=0x00, chreq_reason=0x03)
<0007> fsm.c:299 SUBSCR_CONN[0xce7910]{INIT}: Allocated
<000f> fsm.c:299 LCLS[0xce7a40]{NO_LCLS}: Allocated
<000f> fsm.c:329 LCLS[0xce7a40]{NO_LCLS}: is child of SUBSCR_CONN[0xce7910]

OSMO-BSC CLI:
OsmoBSC# show network
BSC is on MCC-MNC 101-01 and has 1 BTS

  Encryption: A5/0
  NECI (TCH/H): 0
  Use TCH for Paging any: 0
  Handover: Off
  Current Channel Load:
             CCCH+SDCCH4:  25% (1/4)
                   TCH/F:   0% (0/6)
                  SDCCH8:   0% (0/8)
  Last RF Command:
  Last RF Lock Command:


OsmoBSC# show run

Current configuration:
!
!
 bts 0
  type sysmobts
  band GSM900
  cell_identity 6966
  location_area_code 20259
  base_station_id_code 63
  ms max power 15
  cell reselection hysteresis 4
  rxlev access min 0
  radio-link-timeout 32
  channel allocator ascending
  rach tx integer 9
  rach max transmission 7
  channel-descrption attach 1
  channel-descrption bs-pa-mfrms 5
  channel-descrption bs-ag-blks-res 1
  no access-control-class-ramping
  access-control-class-ramping-step-interval dynamic
  access-control-class-ramping-step-size 1
  early-classmark-sending forbidden
  early-classmark-sending-3g allowed
  ip.access unit_id 1800 0
  oml ip.access stream_id 255 line 0
  neighbor-list mode manual-si5
  neighbor-list add arfcn 100
  neighbor-list add arfcn 200
  si5 neighbor-list add arfcn 10
  si5 neighbor-list add arfcn 20
  codec-support fr hr efr amr
  gprs mode none
  no force-combined-si
  trx 0
   rf_locked 0
   arfcn 111
   nominal power 23
   max_power_red 20
   rsl e1 tei 0
   timeslot 0
    phys_chan_config CCCH+SDCCH4
    hopping enabled 0
   timeslot 1
    phys_chan_config SDCCH8
    hopping enabled 0
   timeslot 2
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 3
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 4
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 5
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 6
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 7
    phys_chan_config SDCCH8+CBCH
    hopping enabled 0
  trx 1
   rf_locked 0
   arfcn 13
   nominal power 23
   max_power_red 20
   rsl e1 tei 0
   timeslot 0
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 1
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 2
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 3
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 4
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 5
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 6
    phys_chan_config TCH/F
    hopping enabled 0
   timeslot 7
    phys_chan_config TCH/F
    hopping enabled 0

OSMO-BTS-TRX CLI:
OsmoBTS# show run

Current configuration:
!
!
line vty
 no login
!
e1_input
 e1_line 0 driver ipa
 e1_line 0 port 0
 no e1_line 0 keepalive
phy 0
 osmotrx ip local 127.0.0.1
 osmotrx ip remote 127.0.0.1
 no osmotrx ms-power-loop
 osmotrx timing-advance-loop
 osmotrx base-port local 5800
 osmotrx base-port remote 5700
 osmotrx fn-advance 5
 osmotrx rts-advance 5
 instance 0
  osmotrx rx-gain 0
  osmotrx tx-attenuation 7
 instance 1
  osmotrx rx-gain 0
  osmotrx tx-attenuation 7
bts 0
 band GSM900
 ipa unit-id 1800 0
 oml remote-ip 5.40.0.1
 rtp jitter-buffer 100
 rtp port-range 16384 17407
 paging queue-size 200
 paging lifetime 0
 uplink-power-target -75
 gsmtap-sapi ccch
 gsmtap-sapi pdtch
 min-qual-rach 50
 min-qual-norm -5
 max-ber10k-rach 1707
 trx 0
  power-ramp max-initial 0 mdBm
  power-ramp step-size 2000 mdB
  power-ramp step-interval 1
  ms-power-control dsp
  phy 0 instance 0
 trx 1
  power-ramp max-initial 0 mdBm
  power-ramp step-size 2000 mdB
  power-ramp step-interval 1
  ms-power-control dsp
  phy 0 instance 1
end

OSMO-TRX CLI:
OsmoTRX# show run

Current configuration:
!
!
stats interval 5
!
line vty
 no login
!
trx
 bind-ip 127.0.0.1
 remote-ip 127.0.0.1
 multi-arfcn disable
 swap-channels disable
 egprs disable
 chan 0
 chan 1
end

Best Regard,

Ron Menez
ron.menez at entropysolution.com<mailto:ron.menez at entropysolution.com>




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