Cellular Network Infrastructure » Core Network (CN) » OsmoMSC

Similarly to TC_mm_id_resp_no_identity (see #6426), TC_mo_ussd_for_unknown_trans fails sporadically from time to time:

Timeout waiting for ClearCommand/Release
      MSC_Tests.ttcn:7385 MSC_Tests control part
      MSC_Tests.ttcn:4117 TC_mo_ussd_for_unknown_trans testcase

Looking at the PCAP (attached), I think the problem is similar to what we saw in #6426:

  687   1.336828          193 → 185          BSSAP 152 CR (BSSMAP) Complete Layer 3 Information (DTAP) (MM) CM Service Request 
  831   1.340281          185 → 193          BSSAP 112 DT1 (BSSMAP) Common Id 
  834   1.340374          185 → 193          BSSAP 104 DT1 (DTAP) (MM) CM Service Accept 
  841   1.351329          193 → 185          BSSAP/GSM MAP 152 SACK (Ack=12, Arwnd=106496) DT1 (DTAP) (SS) Facility (GSM MAP) returnError [Malformed Packet]
  891   1.353538          185 → 193          BSSAP 120 SACK (Ack=9, Arwnd=106496) DT1 (DTAP) (SS) Release Complete 
  926   6.340854          185 → 193          BSSAP 108 DT1 (BSSMAP) Clear Command 

For some reason, it takes osmo-msc 5 seconds to clear the connection. And this is again related to the X1 timeout:

  895   6.339359 172.18.13.10 → 172.18.13.103 GSMTAP 294 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_AUTHENTICATED}: Timeout of X1 
  896   6.339410 172.18.13.10 → 172.18.13.103 GSMTAP 313 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_AUTHENTICATED}: Received Event MSC_A_EV_CN_CLOSE 
  897   6.339428 172.18.13.10 → 172.18.13.103 GSMTAP 325 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_AUTHENTICATED}: State change to MSC_A_ST_RELEASING (X2, 30s) 
  898   6.339447 172.18.13.10 → 172.18.13.103 GSMTAP 318 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: Releasing: msc_a use is 1 (cm_service_ss) 
  899   6.339476 172.18.13.10 → 172.18.13.103 GSMTAP 312 VLR subscr IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187 + msc_a_fsm_releasing_onenter: now used by 3 (attached,active-conn,msc_a_fsm_releasing_onenter) 
  900   6.339491 172.18.13.10 → 172.18.13.103 GSMTAP 342 VLR subscr IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187 + vlr_subscr_cancel_attach_fsm: now used by 4 (attached,active-conn,msc_a_fsm_releasing_onenter,vlr_subscr_cancel_attach_fsm) 
  901   6.339506 172.18.13.10 → 172.18.13.103 GSMTAP 313 VLR subscr IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187 - vlr_subscr_cancel_attach_fsm: now used by 3 (attached,active-conn,msc_a_fsm_releasing_onenter) 
  902   6.339524 172.18.13.10 → 172.18.13.103 GSMTAP 334 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: Releasing: canceling still pending use: cm_service_ss (1) 
  903   6.339539 172.18.13.10 → 172.18.13.103 GSMTAP 311 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: - cm_service_ss: now used by 0 (-) 
  904   6.339551 172.18.13.10 → 172.18.13.103 GSMTAP 307 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: Received Event MSC_A_EV_UNUSED 
  905   6.339566 172.18.13.10 → 172.18.13.103 GSMTAP 335 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: + wait-Clear-Complete: now used by 1 (wait-Clear-Complete) 
  906   6.339586 172.18.13.10 → 172.18.13.103 GSMTAP 310 msc_a(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9d2b50]{MSC_A_ST_RELEASING}: RAN encode: BSSMAP: CLEAR_COMMAND 
  907   6.339604 172.18.13.10 → 172.18.13.103 GSMTAP 328 msc_i(IMSI-262420000000111:MSISDN-491230000111:TMSI-0x109C9187:GERAN-A-128:CM_SERVICE_REQ)[0x55f81e9cf570]{READY}: Received Event MSC_I_EV_FROM_A_FORWARD_ACCESS_SIGNALLING_REQUEST 
  908   6.339631 172.18.13.10 → 172.18.13.103 GSMTAP 259 ran_peer(GERAN-A:RI-SSN_PC:PC-0-24-1:SSN-BSSAP)[0x55f81e9b20a0]{READY}: Received Event RAN_PEER_EV_MSG_DOWN_CO