diff options
Diffstat (limited to 'doc/assignment.msc')
| -rw-r--r-- | doc/assignment.msc | 248 |
1 files changed, 92 insertions, 156 deletions
diff --git a/doc/assignment.msc b/doc/assignment.msc index d470d014b..9f10ea1ba 100644 --- a/doc/assignment.msc +++ b/doc/assignment.msc @@ -1,190 +1,126 @@ msc { hscale=3; - ms [label="MS"], bts [label="BTS"], bsc[label="BSC"], bsc_gscon[label="BSC conn FSM"], bsc_mgcp[label="BSC mgcp FSM"], mgw[label="MGW"], msc_[label="MSC"]; + ms [label="MS/BTS"], bsc_lchan[label="BSC lchan FSM"], + bsc_gscon[label="BSC conn FSM"], bsc_mgcp[label="BSC mgcp FSM"], mgw_msc[label="MGW/MSC"]; - ms note msc_ [label="lchan allocation sequence for BSSMAP Assignment Request"]; + ms note mgw_msc [label="lchan allocation sequence for BSSMAP Assignment Request"]; - bsc <= msc_ [label="BSSMAP Assignment Request"]; - bsc box bsc [label="bssmap_handle_assignm_req()"]; - bsc -> bsc_gscon [label="GSCON_EV_A_ASSIGNMENT_CMD"]; + bsc_gscon <= mgw_msc [label="BSSMAP Assignment Request"]; + bsc_gscon abox bsc_gscon [label="ST_ASSIGNMENT_\nWAIT_LCHAN"]; - --- [label="is the chan_mode a speech mode?"]; + bsc_lchan <- bsc_gscon [label="lchan_select_by_chan_mode(chan_mode)"]; + |||; + --- [label="IF returned lchan is NULL"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; + ---; + |||; + bsc_gscon box bsc_gscon [label="store lchan pointer in conn->lchan_for_assignment"]; + bsc_lchan <- bsc_gscon [label="lchan_activate(FOR_ASSIGNMENT)"]; + ...; + |||; + --- [label="on lchan FSM error or timeout"]; + bsc_lchan -> bsc_gscon [label="GSCON_EV_LCHAN_ALLOC_ERROR"]; + bsc_gscon box bsc_gscon [label="'forget' all about conn->lchan_for_assignment"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; + --- [label="END: 'on error'"]; + ...; + ...; - bsc_gscon abox bsc_gscon [label="ST_WAIT_CRCX_BTS (MGCP_MGW_TIMEOUT = 4s)"]; + --- [label="IF lchan FSM decides that it is an lchan for speech"]; + bsc_lchan -> bsc_gscon [label="GSCON_EV_ENSURE_MGW_ENDPOINT"]; + --- [label="IF there is an MGW endpoint for the BTS already (conn->user_plane.fi_bts)"]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_MGW_ENDPOINT_AVAILABLE"]; + --- [label="ELSE: no MGW endpoint for the BTS side yet"]; + bsc_gscon abox bsc_gscon [label="ST_ASSIGNMENT_\nWAIT_CRCX_BTS"]; + bsc_gscon box bsc_gscon [label="assignment_created_mgw_endpoint = true"]; bsc_gscon -> bsc_mgcp [label="mgcp_conn_create()"]; - bsc_mgcp => mgw [label="CRCX (for BTS)"]; - bsc_mgcp abox bsc_mgcp [label="ST_CRCX (MGCP_MGW_TIMEOUT = 4s)"]; - bsc_gscon note bsc_mgcp [label="two timeouts running in parallel"]; - bsc_gscon note bsc_mgcp [label="note: #define MGCP_MGW_TIMEOUT exists twice, - once in libosmo-mgcp-client, - once in bsc_subscr_conn_fsm.c"]; - bsc_mgcp -> bsc_gscon [label="mgcp_conn_create() exits"]; - bsc_gscon -> bsc [label="bssmap_handle_assignm_req() exits"]; + bsc_mgcp abox bsc_mgcp [label="ST_CRCX_RESP (MGCP_MGW_TIMEOUT = 4s)"]; + bsc_mgcp => mgw_msc [label="CRCX (for BTS)"]; + bsc_gscon note bsc_mgcp [label="conn FSM relies on mgcp FSM timeout"]; ...; --- [label="On Timeout"]; - bsc_gscon note bsc_gscon [label="The conn FSM likely timeouts first"]; - bsc_gscon => msc_ [label="BSSMAP Assignment Failure"]; - bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; - bsc_mgcp note bsc_mgcp [label="The MGCP FSM will timeout right after that, and terminate itself, - emitting the parent_term event set upon mgcp_conn_create():"]; + bsc_mgcp note bsc_mgcp [label="On timeouit, the MGCP FSM will terminate, emitting the parent_term + event set upon mgcp_conn_create():"]; bsc_mgcp -> bsc_gscon [label="GSCON_EV_MGW_FAIL_BTS"]; bsc_gscon note bsc_gscon [label="GSCON_EV_MGW_FAIL_BTS is handled by the conn FSM allstate - handler. It sets conn->user_plane.fi_bts = NULL. There is code - that would emit a BSSMAP Assignment Failure, but not in - ST_ACTIVE"]; - --- [label="end: 'On Timeout'"]; + handler. It sets conn->user_plane.fi_bts = NULL."]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_MGW_ENDPOINT_ERROR"]; + bsc_lchan note bsc_gscon [label="conn FSM timeout handler exits and relies on the lchan FSM + signalling error, which should actually happen immediately:"]; + bsc_gscon <- bsc_lchan [label="GSCON_EV_LCHAN_ALLOC_ERROR"]; + bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; + bsc_gscon box bsc_gscon [label="'forget' all about conn->lchan_for_assignment"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + --- [label="END: 'On Timeout'"]; ...; - bsc_mgcp <= mgw [label="CRCX OK (for BTS)"]; + bsc_mgcp <= mgw_msc [label="CRCX OK (for BTS)"]; bsc_mgcp box bsc_mgcp [label="libosmo-mgcp-client fsm_crcx_resp_cb()"]; + bsc_mgcp abox bsc_mgcp [label="ST_READY"]; bsc_mgcp -> bsc_gscon [label="GSCON_EV_MGW_CRCX_RESP_BTS"]; - --- [label="end: 'is the chan_mode a speech mode?'"]; - - bsc_gscon note bsc_gscon [label="for mode=sign, we're still handling GSCON_EV_A_ASSIGNMENT_CMD; - for speech mode, we're handling GSCON_EV_MGW_CRCX_RESP_BTS"]; - bsc <- bsc_gscon [label="gsm0808_assign_req()"]; - - bsc box bsc [label="lchan_alloc(): pick available lchan"]; - bsc box bsc [label="rsl_chan_activate_lchan()"]; - - --- [label="is the chosen lchan on dynamic timeslot that is currently used as PDCH?"]; - bts <= bsc [label="i) RSL RF Chan Release of PDCH (Osmocom dyn TS)"]; - bts <= bsc [label="OR ii) RSL PDCH Deact (ip.access dyn TS)"]; - bsc -> bsc_gscon [label="gsm0808_assign_req() returns early"]; - bsc_gscon abox bsc_gscon [label="ST_WAIT_ASS_COMPL (GSM0808_T10_VALUE=6s)"]; + bsc_gscon abox bsc_gscon [label="ST_ASSIGNMENT_\nWAIT_LCHAN"]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_MGW_ENDPOINT_AVAILABLE"]; + --- [label="END: lchan FSM decides that it is an lchan for speech"]; ...; - bts note bsc_gscon [linecolor="red", - label="Osmocom style dyn TS use lchan->act_timer to watch over RF Chan Release, but there - seems to be no timer watching over PDCH Deact!"]; ...; - bts => bsc [label="i) RSL RF Chan Release ACK (Osmocom dyn TS)"]; - bts => bsc [label="OR ii) RSL PDCH Deact ACK (ip.access dyn TS)"]; - bsc box bsc [label="rsl_chan_activate_lchan() re-invoked"]; - bsc box bsc [label="lchan->state = LCHAN_S_ACT_REQ"]; - bts <= bsc [label="RSL Chan Activ"]; - --- [label="else (no dyn TS switchover)"]; - - bsc box bsc [label="lchan->state = LCHAN_S_ACT_REQ"]; - bts <= bsc [label="RSL Chan Activ"]; - bsc -> bsc_gscon [label="gsm0808_assign_req() returns"]; - bsc_gscon abox bsc_gscon [label="ST_WAIT_ASS_COMPL (GSM0808_T10_VALUE=6s)"]; - ---; + bsc_lchan -> bsc_gscon [label="GSCON_EV_LCHAN_ACTIVE"]; + bsc_gscon abox bsc_gscon [label="ST_ASSIGNMENT_\nWAIT_COMPLETE\nT10, 6s"]; + ms <= bsc_gscon [label="RR Assignment"]; ...; --- [label="On Timeout"]; - bsc_gscon => msc_ [label="BSSMAP Assignment Failure"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_LCHAN_RELEASE"]; + bsc_gscon box bsc_gscon [label="'forget' all about conn->lchan_for_assignment"]; + --- [label="IF assignment_created_mgw_endpoint == true"]; + bsc_gscon -> bsc_mgcp [label="mgcp_conn_delete()"]; + bsc_gscon note bsc_mgcp [label="If the MGW endpoint didn't exist before the Assignment, release + it now. If there was one before this, it is probably still in use by a previous lchan, so + keep it in place."]; bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; - bsc_gscon note bsc_mgcp [linecolor="red", - label="The mgcp FSM from CRCX above apparently lacks a cleanup action for this case. - It should be cleaned up eventually when the conn is torn down, but we should - release RTP endpoints as soon as possible."]; - --- [label="end: 'On Timeout'"]; - ...; - - bts => bsc [label="RSL Chan Activ ACK"]; - bsc box bsc [label="rsl_rx_chan_act_ack()"]; - bsc box bsc [label="Stop lchan->act_timer"]; - bsc box bsc [label="lchan->state = LCHAN_S_ACTIVE"]; - bsc -> bsc [label="S_LCHAN_ACTIVATE_ACK"]; - bsc box bsc [label="bsc_api.c handle_chan_ack()"]; - ms <= bsc [label="RR Assignment Command"]; - - ...; - ms note bsc_gscon [label="We rely on the overall conn FSM ST_WAIT_ASS_COMPL timeout."]; + --- [label="END: 'On Timeout'"]; ...; - - ms => bsc [label="RR Assignment Complete"]; - bsc box bsc [label="handle_ass_compl()"]; - --- [label="Release old lchan"]; - bsc box bsc [label="_lchan_handle_release(sacch_deact=0)"]; - bsc box bsc [label="rsl_release_sapis_from(start=1)"]; - bts <= bsc [label="RSL Release Request (Local End)..."]; - bts <= bsc [label="...for each SAPI except link_id=0"]; - bsc box bsc [label="rsl_release_request(link_id=0)"]; - bts <= bsc [label="RSL Release Request (Local End) for link_id=0"]; - bsc box bsc [label="_lchan_handle_release() returns here, the remaining release is asynchronous; - see `End: 'Release old lchan'` below."]; - ...; - bts note bsc_gscon [linecolor="red", - label="There seems to be no timer watching over RSL Release Request!"]; - ...; - bts => bsc [label="RSL Release Confirm..."]; - bts => bsc [label="...for each SAPI and link_id=0"]; - bsc abox bsc [label="start T3111"]; - ...; - bsc box bsc [label="T3111 expires"]; - bsc abox bsc [label="Start lchan->act_timer with lchan_deact_tmr_cb"]; - bts <= bsc [label="RSL RF Channel Release"]; - ...; - --- [label="On timeout"]; - bsc box bsc [label="lchan_deact_tmr_cb()"]; - bsc box bsc [label="rsl_lchan_mark_broken(): state=LCHAN_S_BROKEN"]; - bsc box bsc [label="lchan_free()"]; - bsc -> bsc [label="S_LCHAN_UNEXPECTED_RELEASE"]; - bsc box bsc [label="bsc_api.c handle_release()"]; - bsc box bsc [label="bsc->assign_fail()"]; - bsc -> bsc_gscon [label="GSCON_EV_RR_ASS_FAIL"]; - bsc note bsc_gscon [linecolor="orange", - label="The name 'RR_ASS_FAIL' might suggest the event means an actual RR Assignment - Failure message being received. Maybe this should be called GSCON_EV_ASSIGNMENT_ERROR."]; - ...; - bsc box bsc [label="bsc->clear_request()"]; - bsc box bsc [label="bsc_clear_request encodes a BSSMAP Clear Request message and passes it on - to the conn FSM as data argument via:"]; - bsc -> bsc_gscon [label="GSCON_EV_TX_SCCP"]; - bsc_gscon => msc_ [label="BSSMAP Clear Request"]; - bsc note bsc_gscon [linecolor="red", - label="Instead of sending an arbitrary message, the conn FSM should - be explicitly instructed to clear the connection, to be able - to notice if the MSC failed to respond to the Clear Request. - Currently, this relies on the MSC responding with a Clear - Command, hopefully, some time later."]; - --- [label="End: 'On timeout'"]; - ...; - bts => bsc [label="RSL RF Channel Release Ack"]; - bsc box bsc [label="Stop lchan->act_timer"]; - bsc box bsc [label="Stop lchan->T3111"]; - --- [label="End: 'Release old lchan'"]; - bsc box bsc [label="still in handle_ass_compl()"]; - bsc note bsc [label="officially take over new lchan: conn->lchan = conn->secondary_lchan"]; - --- [label="is BTS using IPA Abis? (osmo-bts, ip.access)"]; - bts <= bsc [label="IPACC CRCX"]; - ---; - bsc -> bsc [label="handle_ass_compl() calls bsc_api->assign_compl()"]; - --- [label="is BTS using IPA Abis? (osmo-bts, ip.access) && conn->user_plane.rtp_ip"]; - bsc box bsc [label="bsc_assign_compl()"]; - bsc note bsc [label="set ass_compl.valid = true, - postponing GSCON_EV_RR_ASS_COMPL until after the - IPACC MDCX ACK received in osmo_bsc_audio.c"]; - bsc box bsc [label="exit early: bsc_assign_compl()"]; - bsc box bsc [label="exit early: handle_ass_compl()"]; - bsc box bsc [label="osmo_bsc_audio.c"]; - bts => bsc [label="IPACC CRCX ACK"]; - bts <= bsc [label="IPACC MDCX"]; - bts => bsc [label="IPACC MDCX ACK"]; - bsc box bsc [label="handle_abisip_signal()"]; - bsc -> bsc_gscon [label="GSCON_EV_RR_ASS_COMPL"]; - --- [label="else"]; - bsc box bsc [label="bsc_assign_compl()"]; - bsc -> bsc_gscon [label="GSCON_EV_RR_ASS_COMPL"]; - --- ; - - --- [label="is chan_mode a speech mode?"]; + ms => bsc_gscon [label="RR Assignment Complete"]; + bsc_gscon -> bsc_lchan [label="OLD lchan: LCHAN_EV_LCHAN_RELEASE"]; + bsc_gscon box bsc_gscon [label="conn->lchan = conn->lchan_for_assignment"]; + --- [label="IF: chan_mode a speech mode?"]; bsc_gscon abox bsc_gscon [label="ST_WAIT_MDCX_BTS"]; bsc_gscon -> bsc_mgcp [label="mgcp_conn_modify()"]; bsc_mgcp note bsc_mgcp [label="same mgcp FSM as above, for BTS side"]; - bsc_mgcp => mgw [label="MDCX (for BTS)"]; - bsc_mgcp <= mgw [label="MDCX OK"]; + bsc_mgcp abox bsc_mgcp [label="ST_MDCX_RESP"]; + bsc_mgcp => mgw_msc [label="MDCX (for BTS)"]; + ...; + --- [label="On Timeout"]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_RELEASE"]; + bsc_gscon -> bsc_mgcp [label="mgcp_conn_delete()"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + bsc_gscon abox bsc_gscon [label="ST_WAIT_CLEAR_CMD"]; + bsc_gscon => mgw_msc [label="BSSMAP Clear Request"]; + --- [label="END: 'On Timeout'"]; + ...; + bsc_mgcp <= mgw_msc [label="MDCX OK"]; + bsc_mgcp abox bsc_mgcp [label="ST_READY"]; bsc_mgcp -> bsc_gscon [label="GSCON_EV_MGW_MDCX_RESP_BTS"]; bsc_gscon abox bsc_gscon [label="ST_WAIT_CRCX_MSC"]; bsc_gscon -> bsc_mgcp [label="mgcp_conn_create()"]; bsc_mgcp note bsc_mgcp [label="second mgcp FSM for MSC side"]; - bsc_mgcp => mgw [label="CRCX (for MSC)"]; - bsc_mgcp <= mgw [label="CRCX OK (for MSC)"]; + bsc_mgcp => mgw_msc [label="CRCX (for MSC)"]; + ...; + --- [label="On Timeout"]; + bsc_gscon -> bsc_lchan [label="LCHAN_EV_RELEASE"]; + bsc_gscon -> bsc_mgcp [label="mgcp_conn_delete()"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Failure"]; + bsc_gscon abox bsc_gscon [label="ST_WAIT_CLEAR_CMD"]; + bsc_gscon => mgw_msc [label="BSSMAP Clear Request"]; + --- [label="END: 'On Timeout'"]; + ...; + bsc_mgcp <= mgw_msc [label="CRCX OK (for MSC)"]; bsc_gscon <- bsc_mgcp [label="GSCON_EV_MGW_CRCX_RESP_MSC"]; - ---; + --- [label="END: chan_mode a speech mode?"]; - bsc_gscon => msc_ [label="BSSMAP Assignment Complete"]; + bsc_gscon => mgw_msc [label="BSSMAP Assignment Complete"]; bsc_gscon abox bsc_gscon [label="ST_ACTIVE"]; } |