Move timer X2002 to tbf_fsm

Related: OS#2709
Change-Id: I94b71c60ed49d51ebdf6d6b428056b4b94354676

11 files changed, 134 insertions, 86 deletions

diff --git a/src/bts.cpp b/src/bts.cpp
index 729ff5d4..12a1b04b 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -655,11 +655,7 @@ int bts_rcv_imm_ass_cnf(struct gprs_rlcmac_bts *bts, const uint8_t *data, uint32
 	}
 
 	LOGP(DRLCMAC, LOGL_DEBUG, "Got IMM.ASS confirm for TLLI=%08x\n", tlli);
-
-	if (dl_tbf->m_wait_confirm) {
-		/* Transition to FLOW in gprs_rlcmac_tbf::handle_timeout() when timer expires */
-		T_START(dl_tbf, T0, -2002, "assignment (AGCH)", true);
-	}
+	osmo_fsm_inst_dispatch(dl_tbf->state_fsm.fi, TBF_EV_ASSIGN_PCUIF_CNF, NULL);
 
 	return 0;
 }
diff --git a/src/gprs_rlcmac_sched.cpp b/src/gprs_rlcmac_sched.cpp
index 18c07633..d73e55d8 100644
--- a/src/gprs_rlcmac_sched.cpp
+++ b/src/gprs_rlcmac_sched.cpp
@@ -308,10 +308,6 @@ static struct msgb *sched_select_downlink(struct gprs_rlcmac_bts *bts, struct gp
 		 && tbf->state_is_not(TBF_ST_FINISHED))
 			continue;
 
-		/* waiting for CCCH IMM.ASS confirm */
-		if (tbf->m_wait_confirm)
-			continue;
-
 		/* If a GPRS (CS1-4) Dl block is required, skip EGPRS(_GSMK) tbfs: */
 		if (req_mcs_kind == GPRS && tbf->is_egprs_enabled())
 			continue;
diff --git a/src/pdch.cpp b/src/pdch.cpp
index 9477178d..439759fa 100644
--- a/src/pdch.cpp
+++ b/src/pdch.cpp
@@ -369,8 +369,6 @@ void gprs_rlcmac_pdch::rcv_control_ack(Packet_Control_Acknowledgement_t *packet,
 			tbf_free(tbf);
 
 		osmo_fsm_inst_dispatch(new_tbf->state_fsm.fi, TBF_EV_ASSIGN_ACK_PACCH, NULL);
-		/* stop pending assignment timer */
-		new_tbf->t_stop(T0, "control acked (DL-TBF)");
 
 		tbf_assign_control_ts(new_tbf);
 		return;
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 74a44d9b..5efbe7f2 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -59,8 +59,6 @@ extern void *tall_pcu_ctx;
 
 unsigned int next_tbf_ctr_group_id = 0; /* Incrementing group id */
 
-static void tbf_timer_cb(void *_tbf);
-
 const struct value_string gprs_rlcmac_tbf_ul_ack_state_names[] = {
 	OSMO_VALUE_STRING(GPRS_RLCMAC_UL_ACK_NONE),
 	OSMO_VALUE_STRING(GPRS_RLCMAC_UL_ACK_SEND_ACK), /* send acknowledge on next RTS */
@@ -76,7 +74,6 @@ static const struct value_string tbf_counters_names[] = {
 };
 
 static const struct value_string tbf_timers_names[] = {
-	OSMO_VALUE_STRING(T0),
 	OSMO_VALUE_STRING(T3141),
 	OSMO_VALUE_STRING(T3191),
 	OSMO_VALUE_STRING(T3193),
@@ -422,7 +419,6 @@ bool gprs_rlcmac_tbf::timers_pending(enum tbf_timers t)
 	if (t != T_MAX)
 		return osmo_timer_pending(&Tarr[t]);
 
-	/* we don't start with T0 because it's internal timer which requires special handling */
 	for (i = T3141; i < T_MAX; i++)
 		if (osmo_timer_pending(&Tarr[i]))
 			return true;
@@ -433,8 +429,7 @@ bool gprs_rlcmac_tbf::timers_pending(enum tbf_timers t)
 void gprs_rlcmac_tbf::stop_timers(const char *reason)
 {
 	uint8_t i;
-	/* we start with T0 because timer reset does not require any special handling */
-	for (i = T0; i < T_MAX; i++)
+	for (i = T3141; i < T_MAX; i++)
 		t_stop((enum tbf_timers)i, reason);
 }
 
@@ -502,9 +497,6 @@ void gprs_rlcmac_tbf::t_start(enum tbf_timers t, int T, const char *reason, bool
 	Tarr[t].data = this;
 
 	switch(t) {
-	case T0:
-		Tarr[t].cb = tbf_timer_cb;
-		break;
 	case T3141:
 		Tarr[t].cb = cb_T3141;
 		break;
@@ -594,7 +586,6 @@ void gprs_rlcmac_tbf::set_polling(uint32_t new_poll_fn, uint8_t ts, enum pdch_ul
 
 void gprs_rlcmac_tbf::poll_timeout(struct gprs_rlcmac_pdch *pdch, uint32_t poll_fn, enum pdch_ulc_tbf_poll_reason reason)
 {
-	uint16_t pgroup;
 	gprs_rlcmac_ul_tbf *ul_tbf = as_ul_tbf(this);
 
 	LOGPTBF(this, LOGL_NOTICE, "poll timeout for FN=%d, TS=%d (curr FN %d)\n",
@@ -645,7 +636,8 @@ void gprs_rlcmac_tbf::poll_timeout(struct gprs_rlcmac_pdch *pdch, uint32_t poll_
 		/* Timeout waiting for CTRL ACK acking Pkt Cell Change Continue */
 		osmo_fsm_inst_dispatch(m_ms->nacc->fi, NACC_EV_TIMEOUT_CELL_CHG_CONTINUE, NULL);
 		return;
-	} else if (direction == GPRS_RLCMAC_DL_TBF) {
+	} else if (reason == PDCH_ULC_POLL_DL_ACK) {
+		/* POLL Timeout expecting DL ACK/NACK: implies direction == GPRS_RLCMAC_DL_TBF */
 		gprs_rlcmac_dl_tbf *dl_tbf = as_dl_tbf(this);
 
 		if (!(dl_tbf->state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_TO_DL_ACK))) {
@@ -669,16 +661,7 @@ void gprs_rlcmac_tbf::poll_timeout(struct gprs_rlcmac_pdch *pdch, uint32_t poll_
 			return;
 		}
 		/* resend IMM.ASS on CCCH on timeout */
-		if ((dl_tbf->state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))
-		 && !(dl_tbf->state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_DL_ACK))) {
-			LOGPTBF(dl_tbf, LOGL_DEBUG, "Re-send dowlink assignment on PCH (IMSI=%s)\n",
-				imsi());
-			/* send immediate assignment */
-			if ((pgroup = imsi2paging_group(imsi())) > 999)
-				LOGPTBF(dl_tbf, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi());
-			bts_snd_dl_ass(dl_tbf->bts, dl_tbf, pgroup);
-			dl_tbf->m_wait_confirm = 1;
-		}
+		osmo_fsm_inst_dispatch(this->state_fsm.fi, TBF_EV_DL_ACKNACK_MISS, NULL);
 	} else
 		LOGPTBF(this, LOGL_ERROR, "Poll Timeout, but no event!\n");
 }
@@ -729,48 +712,6 @@ int gprs_rlcmac_tbf::setup(int8_t use_trx, bool single_slot)
 	return 0;
 }
 
-static void tbf_timer_cb(void *_tbf)
-{
-	struct gprs_rlcmac_tbf *tbf = (struct gprs_rlcmac_tbf *)_tbf;
-	tbf->handle_timeout();
-}
-
-void gprs_rlcmac_tbf::handle_timeout()
-{
-	int current_fn = bts_current_frame_number(bts);
-
-	LOGPTBF(this, LOGL_DEBUG, "timer 0 expired. cur_fn=%d\n", current_fn);
-
-	/* Finish waiting after IMM.ASS confirm timer for CCCH assignment (see timer X2002) */
-	if ((state_fsm.state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))) {
-		gprs_rlcmac_dl_tbf *dl_tbf = as_dl_tbf(this);
-		dl_tbf->m_wait_confirm = 0;
-		if (dl_tbf->state_is(TBF_ST_ASSIGN)) {
-			tbf_assign_control_ts(dl_tbf);
-
-			if (!dl_tbf->upgrade_to_multislot) {
-				/* change state to FLOW, so scheduler
-				 * will start transmission */
-				osmo_fsm_inst_dispatch(dl_tbf->state_fsm.fi, TBF_EV_ASSIGN_READY_CCCH, NULL);
-				return;
-			}
-
-			/* This tbf can be upgraded to use multiple DL
-			 * timeslots and now that there is already one
-			 * slot assigned send another DL assignment via
-			 * PDCH. */
-
-			/* keep to flags */
-			dl_tbf->state_fsm.state_flags &= GPRS_RLCMAC_FLAG_TO_MASK;
-
-			dl_tbf->update();
-
-			dl_tbf->trigger_ass(dl_tbf);
-		} else
-			LOGPTBF(dl_tbf, LOGL_NOTICE, "Continue flow after IMM.ASS confirm\n");
-	}
-}
-
 int gprs_rlcmac_tbf::establish_dl_tbf_on_pacch()
 {
 	struct gprs_rlcmac_dl_tbf *new_tbf = NULL;
@@ -977,6 +918,16 @@ bool tbf_is_control_ts(const struct gprs_rlcmac_tbf *tbf, uint8_t ts)
 	return tbf->is_control_ts(ts);
 }
 
+bool tbf_can_upgrade_to_multislot(const struct gprs_rlcmac_tbf *tbf)
+{
+	return tbf->upgrade_to_multislot;
+}
+
+int tbf_update(struct gprs_rlcmac_tbf *tbf)
+{
+	return tbf->update();
+}
+
 const char* tbf_rlcmac_diag(const struct gprs_rlcmac_tbf *tbf)
 {
 	static char buf[256];
diff --git a/src/tbf.h b/src/tbf.h
index 4218cf58..84c3d394 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -100,9 +100,6 @@ extern unsigned int next_tbf_ctr_group_id;
 #define LOGPTBF(tbf, level, fmt, args...) LOGP(DTBF, level, "%s " fmt, tbf_name(tbf), ## args)
 
 enum tbf_timers {
-	/* internal assign/reject timer */
-	T0,
-
 	/* Wait contention resolution success on UL TBFs assigned over CCCH */
 	T3141,
 
@@ -164,6 +161,8 @@ void tbf_poll_timeout(struct gprs_rlcmac_tbf *tbf, struct gprs_rlcmac_pdch *pdch
 void tbf_update_state_fsm_name(struct gprs_rlcmac_tbf *tbf);
 const char* tbf_rlcmac_diag(const struct gprs_rlcmac_tbf *tbf);
 bool tbf_is_control_ts(const struct gprs_rlcmac_tbf *tbf, uint8_t ts);
+bool tbf_can_upgrade_to_multislot(const struct gprs_rlcmac_tbf *tbf);
+int tbf_update(struct gprs_rlcmac_tbf *tbf);
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 10492d90..bed7a08c 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -191,7 +191,6 @@ gprs_rlcmac_dl_tbf::~gprs_rlcmac_dl_tbf()
 gprs_rlcmac_dl_tbf::gprs_rlcmac_dl_tbf(struct gprs_rlcmac_bts *bts_, GprsMs *ms) :
 	gprs_rlcmac_tbf(bts_, ms, GPRS_RLCMAC_DL_TBF),
 	m_tx_counter(0),
-	m_wait_confirm(0),
 	m_dl_ack_requested(false),
 	m_last_dl_poll_fn(-1),
 	m_last_dl_drained_fn(-1),
@@ -622,7 +621,6 @@ void gprs_rlcmac_dl_tbf::trigger_ass(struct gprs_rlcmac_tbf *old_tbf)
 		if ((pgroup = imsi2paging_group(imsi())) > 999)
 			LOGPTBFDL(this, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi());
 		bts_snd_dl_ass(bts, this, pgroup);
-		m_wait_confirm = 1;
 	}
 }
 
@@ -1170,7 +1168,6 @@ int gprs_rlcmac_dl_tbf::release()
 
 	/* reset rlc states */
 	m_tx_counter = 0;
-	m_wait_confirm = 0;
 	m_window.reset();
 
 	osmo_fsm_inst_dispatch(this->state_fsm.fi, TBF_EV_ASSIGN_DEL_CCCH, NULL);
@@ -1464,3 +1461,8 @@ struct gprs_rlcmac_dl_tbf *as_dl_tbf(struct gprs_rlcmac_tbf *tbf)
 	else
 		return NULL;
 }
+
+void tbf_dl_trigger_ass(struct gprs_rlcmac_dl_tbf *tbf, struct gprs_rlcmac_tbf *old_tbf)
+{
+	return tbf->trigger_ass(old_tbf);
+}
diff --git a/src/tbf_dl.h b/src/tbf_dl.h
index 97193276..ad1469ad 100644
--- a/src/tbf_dl.h
+++ b/src/tbf_dl.h
@@ -71,7 +71,6 @@ struct gprs_rlcmac_dl_tbf : public gprs_rlcmac_tbf {
 	 * variables are in both (dl and ul) structs and not outside union.
 	 */
 	int32_t m_tx_counter; /* count all transmitted blocks */
-	uint8_t m_wait_confirm; /* wait for CCCH IMM.ASS cnf */
 	bool m_dl_ack_requested;
 	int32_t m_last_dl_poll_fn;
 	int32_t m_last_dl_drained_fn;
@@ -153,6 +152,7 @@ int dl_tbf_handle(struct gprs_rlcmac_bts *bts,
 		  const uint8_t egprs_ms_class, const uint16_t delay_csec,
 		  const uint8_t *data, const uint16_t len);
 
+void tbf_dl_trigger_ass(struct gprs_rlcmac_dl_tbf *tbf, struct gprs_rlcmac_tbf *old_tbf);
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/tbf_fsm.c b/src/tbf_fsm.c
index 0dbf04c8..42c5118e 100644
--- a/src/tbf_fsm.c
+++ b/src/tbf_fsm.c
@@ -46,6 +46,8 @@ const struct value_string tbf_fsm_event_names[] = {
 	{ TBF_EV_ASSIGN_DEL_CCCH, "ASSIGN_DEL_CCCH" },
 	{ TBF_EV_ASSIGN_ACK_PACCH, "ASSIGN_ACK_PACCH" },
 	{ TBF_EV_ASSIGN_READY_CCCH, "ASSIGN_READY_CCCH" },
+	{ TBF_EV_ASSIGN_PCUIF_CNF, "ASSIGN_PCUIF_CNF" },
+	{ TBF_EV_DL_ACKNACK_MISS, "DL_ACKNACK_MISS" },
 	{ TBF_EV_LAST_DL_DATA_SENT, "LAST_DL_DATA_SENT" },
 	{ TBF_EV_LAST_UL_DATA_RECVD, "LAST_UL_DATA_RECVD" },
 	{ TBF_EV_FINAL_ACK_RECVD, "FINAL_ACK_RECVD" },
@@ -136,12 +138,17 @@ static void st_assign_on_enter(struct osmo_fsm_inst *fi, uint32_t prev_state)
 			"Starting timer X2001 [assignment (PACCH)] with %u sec. %u microsec\n",
 			sec, micro);
 		osmo_timer_schedule(&fi->timer, sec, micro);
+	} else if (tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF) {
+		 /* GPRS_RLCMAC_FLAG_CCCH is set, so here we submitted an DL Ass through PCUIF on CCCH */
 	}
 }
 
 static void st_assign(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
 	struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
+	unsigned long val;
+	unsigned int sec, micro;
+
 	switch (event) {
 	case TBF_EV_ASSIGN_ADD_CCCH:
 		mod_ass_type(ctx, GPRS_RLCMAC_FLAG_CCCH, true);
@@ -160,6 +167,23 @@ static void st_assign(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 		}
 		tbf_fsm_state_chg(fi, TBF_ST_FLOW);
 		break;
+	case TBF_EV_ASSIGN_PCUIF_CNF:
+		/* BTS informs us it sent Imm Ass for DL TBF over CCCH. We now
+		 * have to wait for X2002 to trigger (meaning MS is already
+		 * listening on PDCH) in order to move to FLOW state and start
+		 * transmitting data to it. When X2002 triggers (see cb timer
+		 * end of the file) it will send  TBF_EV_ASSIGN_READY_CCCH back
+		 * to us here. */
+		OSMO_ASSERT(tbf_direction(ctx->tbf) == GPRS_RLCMAC_DL_TBF);
+		fi->T = -2002;
+		val = osmo_tdef_get(the_pcu->T_defs, fi->T, OSMO_TDEF_MS, -1);
+		sec = val / 1000;
+		micro = (val % 1000) * 1000;
+		LOGPTBF(ctx->tbf, LOGL_DEBUG,
+			"Starting timer X2002 [assignment (AGCH)] with %u sec. %u microsec\n",
+			sec, micro);
+		osmo_timer_schedule(&fi->timer, sec, micro);
+		break;
 	case TBF_EV_ASSIGN_READY_CCCH:
 		/* change state to FLOW, so scheduler will start transmission */
 		tbf_fsm_state_chg(fi, TBF_ST_FLOW);
@@ -172,7 +196,28 @@ static void st_assign(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 static void st_flow(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
 	struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
+
 	switch (event) {
+	case TBF_EV_DL_ACKNACK_MISS:
+		/* DL TBF: we missed a DL ACK/NACK. If we started assignment
+		 * over CCCH and never received any DL ACK/NACK yet, it means we
+		 * don't even know if the MS successfuly received the Imm Ass on
+		 * CCCH and hence is listening on PDCH. Let's better refrain
+		 * from continuing and start assignment on CCCH again */
+		if ((ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_CCCH))
+		     && !(ctx->state_flags & (1 << GPRS_RLCMAC_FLAG_DL_ACK))) {
+			struct GprsMs *ms = tbf_ms(ctx->tbf);
+			const char *imsi = ms_imsi(ms);
+			uint16_t pgroup;
+			LOGPTBF(ctx->tbf, LOGL_DEBUG, "Re-send dowlink assignment on PCH (IMSI=%s)\n",
+				imsi);
+			tbf_fsm_state_chg(fi, TBF_ST_ASSIGN);
+			/* send immediate assignment */
+			if ((pgroup = imsi2paging_group(imsi)) > 999)
+				LOGPTBF(ctx->tbf, LOGL_ERROR, "IMSI to paging group failed! (%s)\n", imsi);
+			bts_snd_dl_ass(ms->bts, ctx->tbf, pgroup);
+		}
+		break;
 	case TBF_EV_LAST_DL_DATA_SENT:
 	case TBF_EV_LAST_UL_DATA_RECVD:
 		/* All data has been sent or received, change state to FINISHED */
@@ -201,6 +246,8 @@ static void st_finished(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
 	struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
 	switch (event) {
+	case TBF_EV_DL_ACKNACK_MISS:
+		break;
 	case TBF_EV_FINAL_ACK_RECVD:
 		/* We received Final Ack (DL ACK/NACK) from MS. move to
 		   WAIT_RELEASE, we wait there for release or re-use the TBF in
@@ -267,10 +314,42 @@ static void tbf_fsm_cleanup(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause c
 	 */
 }
 
+static void handle_timeout_X2002(struct tbf_fsm_ctx *ctx)
+{
+	struct gprs_rlcmac_dl_tbf *dl_tbf = as_dl_tbf(ctx->tbf);
+
+	if (ctx->fi->state == TBF_ST_ASSIGN) {
+		tbf_assign_control_ts(ctx->tbf);
+
+		if (!tbf_can_upgrade_to_multislot(ctx->tbf)) {
+			/* change state to FLOW, so scheduler
+			 * will start transmission */
+			osmo_fsm_inst_dispatch(ctx->fi, TBF_EV_ASSIGN_READY_CCCH, NULL);
+			return;
+		}
+
+		/* This tbf can be upgraded to use multiple DL
+		 * timeslots and now that there is already one
+		 * slot assigned send another DL assignment via
+		 * PDCH. */
+
+		/* keep to flags */
+		ctx->state_flags &= GPRS_RLCMAC_FLAG_TO_MASK;
+
+		tbf_update(ctx->tbf);
+
+		tbf_dl_trigger_ass(dl_tbf, ctx->tbf);
+	} else
+		LOGPTBF(ctx->tbf, LOGL_NOTICE, "Continue flow after IMM.ASS confirm\n");
+}
+
 static int tbf_fsm_timer_cb(struct osmo_fsm_inst *fi)
 {
 	struct tbf_fsm_ctx *ctx = (struct tbf_fsm_ctx *)fi->priv;
 	switch (fi->T) {
+	case -2002:
+		handle_timeout_X2002(ctx);
+		break;
 	case -2001:
 		LOGPTBF(ctx->tbf, LOGL_NOTICE, "releasing due to PACCH assignment timeout.\n");
 		/* fall-through */
@@ -301,6 +380,7 @@ static struct osmo_fsm_state tbf_fsm_states[] = {
 			X(TBF_EV_ASSIGN_ADD_CCCH) |
 			X(TBF_EV_ASSIGN_ADD_PACCH) |
 			X(TBF_EV_ASSIGN_ACK_PACCH) |
+			X(TBF_EV_ASSIGN_PCUIF_CNF) |
 			X(TBF_EV_ASSIGN_READY_CCCH),
 		.out_state_mask =
 			X(TBF_ST_FLOW) |
@@ -312,12 +392,14 @@ static struct osmo_fsm_state tbf_fsm_states[] = {
 	},
 	[TBF_ST_FLOW] = {
 		.in_event_mask =
+			X(TBF_EV_DL_ACKNACK_MISS) |
 			X(TBF_EV_LAST_DL_DATA_SENT) |
 			X(TBF_EV_LAST_UL_DATA_RECVD) |
 			X(TBF_EV_FINAL_ACK_RECVD) |
 			X(TBF_EV_MAX_N3101) |
 			X(TBF_EV_MAX_N3105),
 		.out_state_mask =
+			X(TBF_ST_ASSIGN) |
 			X(TBF_ST_FINISHED) |
 			X(TBF_ST_WAIT_RELEASE) |
 			X(TBF_ST_RELEASING),
@@ -326,6 +408,7 @@ static struct osmo_fsm_state tbf_fsm_states[] = {
 	},
 	[TBF_ST_FINISHED] = {
 		.in_event_mask =
+			X(TBF_EV_DL_ACKNACK_MISS) |
 			X(TBF_EV_FINAL_ACK_RECVD) |
 			X(TBF_EV_MAX_N3103) |
 			X(TBF_EV_MAX_N3105),
diff --git a/src/tbf_fsm.h b/src/tbf_fsm.h
index 9d2919d3..2f63eef2 100644
--- a/src/tbf_fsm.h
+++ b/src/tbf_fsm.h
@@ -32,6 +32,8 @@ enum tbf_fsm_event {
 	TBF_EV_ASSIGN_DEL_CCCH, /* An assignment previously sent over CCCH has been confirmed by MS */
 	TBF_EV_ASSIGN_ACK_PACCH, /*  We received a CTRL ACK confirming assignment started on PACCH */
 	TBF_EV_ASSIGN_READY_CCCH, /* TBF Start Time timer triggered */
+	TBF_EV_ASSIGN_PCUIF_CNF, /* Transmission of IMM.ASS for DL TBF to the MS confirmed by BTS over PCUIF */
+	TBF_EV_DL_ACKNACK_MISS, /* DL TBF: We polled for DL ACK/NACK but we received none (POLL timeout) */
 	TBF_EV_LAST_DL_DATA_SENT, /* DL TBF sends RLCMAC block containing last DL avilable data buffered */
 	TBF_EV_LAST_UL_DATA_RECVD, /* UL TBF sends RLCMAC block containing last UL data (cv=0) */
 	TBF_EV_FINAL_ACK_RECVD, /* DL ACK/NACK with FINAL_ACK=1 received from MS */
diff --git a/tests/tbf/TbfTest.cpp b/tests/tbf/TbfTest.cpp
index 1fcaead7..19611a70 100644
--- a/tests/tbf/TbfTest.cpp
+++ b/tests/tbf/TbfTest.cpp
@@ -219,7 +219,6 @@ static gprs_rlcmac_dl_tbf *create_dl_tbf(struct gprs_rlcmac_bts *bts, uint8_t ms
 	osmo_fsm_inst_dispatch(dl_tbf->dl_ass_fsm.fi, TBF_DL_ASS_EV_SCHED_ASS, NULL);
 	osmo_fsm_inst_dispatch(dl_tbf->state_fsm.fi, TBF_EV_ASSIGN_ADD_CCCH, NULL);
 	osmo_fsm_inst_dispatch(dl_tbf->state_fsm.fi, TBF_EV_ASSIGN_ACK_PACCH, NULL);
-	dl_tbf->m_wait_confirm = 0;
 	check_tbf(dl_tbf);
 
 	*trx_no_ = trx_no;
@@ -591,9 +590,13 @@ static void test_tbf_dl_llc_loss()
 	OSMO_ASSERT(ms_dl_tbf(ms) != NULL);
 
 	/* Here PCU would answer with data_cnf and trigger
-	 * bts_rcv_imm_ass_cnf(), which would set up the timer X2002. In this
-	 * test we go directly to T0 timeout to move it to FLOW state: */
-	ms_dl_tbf(ms)->handle_timeout();
+	 * bts_rcv_imm_ass_cnf(), which would trigger TBF_EV_ASSIGN_PCUIF_CNF.
+	 * That in turn would set up timer X2002. Finally, X2002 timeout
+	 * moves it to FLOW state. We set X2002 timeout to 0 here to get
+	 * immediate trigger through osmo_select_main() */
+	OSMO_ASSERT(osmo_tdef_set(the_pcu->T_defs, -2002, 0, OSMO_TDEF_MS) == 0);
+	osmo_fsm_inst_dispatch(ms_dl_tbf(ms)->state_fsm.fi, TBF_EV_ASSIGN_PCUIF_CNF, NULL);
+	osmo_select_main(0);
 	OSMO_ASSERT(ms_dl_tbf(ms)->state_is(TBF_ST_FLOW));
 
 	/* Get first BSN */
diff --git a/tests/tbf/TbfTest.err b/tests/tbf/TbfTest.err
index b66707a7..e5664ef2 100644
--- a/tests/tbf/TbfTest.err
+++ b/tests/tbf/TbfTest.err
@@ -1681,7 +1681,9 @@ TBF(DL-TFI_0){NULL}: state_chg to ASSIGN
 TBF(TFI=0 TLLI=0xc0123456 DIR=DL STATE=ASSIGN) TX: START Immediate Assignment Downlink (PCH)
  - TRX=0 (0) TS=4 TA=0
 TBF(TFI=0 TLLI=0xc0123456 DIR=DL STATE=ASSIGN) appending 19 bytes
-TBF(TFI=0 TLLI=0xc0123456 DIR=DL STATE=ASSIGN) timer 0 expired. cur_fn=2654167
+TBF(DL-TFI_0){ASSIGN}: Received Event ASSIGN_PCUIF_CNF
+TBF(TFI=0 TLLI=0xc0123456 DIR=DL STATE=ASSIGN) Starting timer X2002 [assignment (AGCH)] with 0 sec. 0 microsec
+TBF(DL-TFI_0){ASSIGN}: Timeout of X2002
 TBF(DL-TFI_0){ASSIGN}: Received Event ASSIGN_READY_CCCH
 TBF(DL-TFI_0){ASSIGN}: state_chg to FLOW
 TBF(TFI=0 TLLI=0xc0123456 DIR=DL STATE=FLOW) downlink (V(A)==0 .. V(S)==0) mcs_mode_restrict=EGPRS
@@ -2047,6 +2049,7 @@ PDCH(bts=0,trx=0,ts=7) Timeout for registered POLL (FN=2654292): TBF(TFI=0 TLLI=
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) poll timeout for FN=2654292, TS=7 (curr FN 2654292)
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) N3105 0 => 1 (< MAX 8)
+TBF(DL-TFI_0){FINISHED}: Received Event DL_ACKNACK_MISS
 PDCH(bts=0,trx=0,ts=7) Received RTS for PDCH: FN=2654296 block_nr=2 scheduling USF=0 for TBF(TFI=0 TLLI=0xf1223344 DIR=UL STATE=FLOW), expect answer on UL FN=2654301
 PDCH(bts=0,trx=0,ts=7) FN=2654296 Scheduling data message at RTS for DL TFI=0 prio=5 mcs_mode_restrict=EGPRS_GMSK-only
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) downlink (V(A)==0 .. V(S)==1) mcs_mode_restrict=EGPRS_GMSK-only
@@ -2107,6 +2110,7 @@ PDCH(bts=0,trx=0,ts=7) Timeout for registered POLL (FN=2654309): TBF(TFI=0 TLLI=
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) poll timeout for FN=2654309, TS=7 (curr FN 2654348)
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xf1223344 DIR=DL STATE=FINISHED) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FINISHED}: Received Event DL_ACKNACK_MISS
 PDCH(bts=0,trx=0,ts=7) Received RTS for PDCH: FN=2654348 block_nr=2 scheduling USF=0 for TBF(TFI=0 TLLI=0xf1223344 DIR=UL STATE=FLOW), expect answer on UL FN=2654353
 UL_ASS_TBF(UL-TFI_1){SEND_ASS}: Received Event CREATE_RLCMAC_MSG
 PDCH(bts=0,trx=0,ts=7) POLL scheduled at FN 2654348 + 13 = 2654361
@@ -4283,10 +4287,12 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 112)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 PDCH(bts=0,trx=0,ts=4) Expiring FN=112 but previous FN=104 is still reserved!
 PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=104): TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=104, TS=4 (curr FN 112)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 2 => 3 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRRRRRRRRRRRRRRRR"(BSN=24)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:25, lost=0, recv=25, skipped=0, bsn=0, info='RRRRRRRRRRRRRRRRRRRRRRRRR.......................................'
@@ -4546,6 +4552,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 91)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRRRRRRRRRRR"(BSN=19)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:20, lost=0, recv=20, skipped=0, bsn=0, info='RRRRRRRRRRRRRRRRRRRR............................................'
@@ -4765,6 +4772,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 69)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRRRRRR"(BSN=14)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:15, lost=0, recv=15, skipped=0, bsn=0, info='RRRRRRRRRRRRRRR.................................................'
@@ -4968,6 +4976,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 60)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRRRR"(BSN=12)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:13, lost=0, recv=13, skipped=0, bsn=0, info='RRRRRRRRRRRRR...................................................'
@@ -5155,6 +5164,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 52)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRR"(BSN=10)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:11, lost=0, recv=11, skipped=0, bsn=0, info='RRRRRRRRRRR.....................................................'
@@ -5318,6 +5328,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 39)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRR"(BSN=7)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:8, lost=0, recv=8, skipped=0, bsn=0, info='RRRRRRRR........................................................'
@@ -5490,6 +5501,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 34)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRRRR"(BSN=10)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:11, lost=0, recv=10, skipped=1, bsn=0, info='xRRRRRRRRRR.....................................................'
@@ -5653,6 +5665,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 30)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRRR"(BSN=8)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:9, lost=0, recv=9, skipped=0, bsn=0, info='RRRRRRRRR.......................................................'
@@ -5805,6 +5818,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 26)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 1 => 2 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RRRRRRRR"(BSN=7)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:8, lost=0, recv=8, skipped=0, bsn=0, info='RRRRRRRR........................................................'
@@ -6119,6 +6133,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=21): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=21, TS=4 (curr FN 63)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 0 => 1 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RR"(BSN=1)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:2, lost=0, recv=2, skipped=0, bsn=0, info='RR..............................................................'
@@ -6213,6 +6228,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=21): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=21, TS=4 (curr FN 63)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 0 => 1 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RR"(BSN=1)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:2, lost=0, recv=2, skipped=0, bsn=0, info='RR..............................................................'
@@ -6307,6 +6323,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 63)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 0 => 1 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RR"(BSN=1)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:2, lost=0, recv=2, skipped=0, bsn=0, info='RR..............................................................'
@@ -6401,6 +6418,7 @@ PDCH(bts=0,trx=0,ts=4) Timeout for registered POLL (FN=17): TBF(TFI=0 TLLI=0xffe
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) poll timeout for FN=17, TS=4 (curr FN 63)
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) Timeout for polling PACKET DOWNLINK ACK: |Assignment was on PACCH|No downlink ACK received yet|
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) N3105 0 => 1 (< MAX 8)
+TBF(DL-TFI_0){FLOW}: Received Event DL_ACKNACK_MISS
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) downlink acknowledge
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) ack:  (BSN=0)"RR"(BSN=1)  R=ACK I=NACK
 TBF(TFI=0 TLLI=0xffeeddcc DIR=DL STATE=FLOW EGPRS) DL analysis, range=0:2, lost=0, recv=2, skipped=0, bsn=0, info='RR..............................................................'