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authorPau Espin Pedrol <pespin@sysmocom.de>2021-07-22 13:25:05 +0200
committerPau Espin Pedrol <pespin@sysmocom.de>2021-07-23 13:36:03 +0200
commit56eda358741a871a519db52a7eae896af503a712 (patch)
treef467ad91b29faed42930dd8ced40c2f16e467d96
parent8e3320ac4835aa4b7cbe71ac3b3ccd4a7c07f20e (diff)
Introduce VTY option to forbid use of TCH for non-voicecall signalling
Usual allocation mechansim, when some signalling channel is needed, first tries to reserve an SDCCH, and if all of them are exhausted, then attempts to reserve a TCH as a last resort. This, however, may cause TCH starvation under certain situations, for instance if there high load on other services (LU, SMS, etc.). Hence, it may be desirable for the operator to forbid reservation of TCH slots once SDCCH become exhausted. This commit is thus adding a VTY command which allows forbidding it. The default behavior (allow using TCH timeslots when SDCCHs are exhausted) is kept as before. The above mentioned prohibition is applied only to non-voicecall related signalling services. That's because voicecall services will end up requiring a TCH anyway, and forbidding reservation of TCH straighaway when SDCCHs are exhausted would mean no voice calls could be initiated while still TCHs would be available. Related: SYS#5548 Change-Id: Ib08027125145df26602069bfb51847063b0ccc0c
-rw-r--r--include/osmocom/bsc/bts.h4
-rw-r--r--include/osmocom/bsc/gsm_data.h5
-rw-r--r--src/osmo-bsc/abis_rsl.c24
-rw-r--r--src/osmo-bsc/bts.c1
-rw-r--r--src/osmo-bsc/bts_vty.c22
-rw-r--r--tests/osmo-bsc.vty25
6 files changed, 67 insertions, 14 deletions
diff --git a/include/osmocom/bsc/bts.h b/include/osmocom/bsc/bts.h
index 72ef8d974..1d566f5d1 100644
--- a/include/osmocom/bsc/bts.h
+++ b/include/osmocom/bsc/bts.h
@@ -454,6 +454,10 @@ struct gsm_bts {
* interference reported in RSL Resource Indication. */
bool chan_alloc_avoid_interf;
+ /* When true (default), TCH can be allocated to serve
+ * non-voicecall-related signalling services when SDCCHs are exhausted */
+ bool chan_alloc_allow_tch_for_signalling;
+
enum neigh_list_manual_mode neigh_list_manual_mode;
/* parameters from which we build SYSTEM INFORMATION */
struct {
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 063294432..5a20e72d2 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -419,6 +419,11 @@ enum gsm_chreq_reason_t {
GSM_CHREQ_REASON_PDCH,
};
+static inline bool gsm_chreq_reason_is_voicecall(enum gsm_chreq_reason_t reason)
+{
+ return reason == GSM_CHREQ_REASON_EMERG || reason == GSM_CHREQ_REASON_CALL;
+}
+
/* lchans 0..3 are SDCCH in combined channel configuration,
use 4 as magic number for BCCH hack - see osmo-bts-../oml.c:opstart_compl() */
#define CCCH_LCHAN 4
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index 8e4916dc0..d5b0d532e 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -2015,17 +2015,19 @@ void abis_rsl_chan_rqd_queue_poll(struct gsm_bts *bts)
* in the code below, all other channel requests will get an SDCCH first
* (if possible). */
- if (!lchan) {
- LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x, retrying with %s\n",
- get_value_string(gsm_chreq_descs, rqd->reason), gsm_lchant_name(GSM_LCHAN_SDCCH),
- rqd->ref.ra, gsm_lchant_name(GSM_LCHAN_TCH_H));
- lchan = lchan_select_by_type(bts, GSM_LCHAN_TCH_H);
- }
- if (!lchan) {
- LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x, retrying with %s\n",
- get_value_string(gsm_chreq_descs, rqd->reason), gsm_lchant_name(GSM_LCHAN_SDCCH),
- rqd->ref.ra, gsm_lchant_name(GSM_LCHAN_TCH_F));
- lchan = lchan_select_by_type(bts, GSM_LCHAN_TCH_F);
+ if (gsm_chreq_reason_is_voicecall(rqd->reason) || bts->chan_alloc_allow_tch_for_signalling) {
+ if (!lchan) {
+ LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x, retrying with %s\n",
+ get_value_string(gsm_chreq_descs, rqd->reason), gsm_lchant_name(GSM_LCHAN_SDCCH),
+ rqd->ref.ra, gsm_lchant_name(GSM_LCHAN_TCH_H));
+ lchan = lchan_select_by_type(bts, GSM_LCHAN_TCH_H);
+ }
+ if (!lchan) {
+ LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x, retrying with %s\n",
+ get_value_string(gsm_chreq_descs, rqd->reason), gsm_lchant_name(GSM_LCHAN_SDCCH),
+ rqd->ref.ra, gsm_lchant_name(GSM_LCHAN_TCH_F));
+ lchan = lchan_select_by_type(bts, GSM_LCHAN_TCH_F);
+ }
}
if (!lchan) {
LOG_BTS(bts, DRSL, LOGL_NOTICE, "CHAN RQD[%s]: no resources for %s 0x%x\n",
diff --git a/src/osmo-bsc/bts.c b/src/osmo-bsc/bts.c
index ec29ac80e..c0d663420 100644
--- a/src/osmo-bsc/bts.c
+++ b/src/osmo-bsc/bts.c
@@ -245,6 +245,7 @@ struct gsm_bts *gsm_bts_alloc(struct gsm_network *net, struct gsm_bts_sm *bts_sm
bts->neigh_list_manual_mode = NL_MODE_AUTOMATIC;
bts->early_classmark_allowed_3g = true; /* 3g Early Classmark Sending controlled by bts->early_classmark_allowed param */
bts->si_unused_send_empty = true;
+ bts->chan_alloc_allow_tch_for_signalling = true;
bts->si_common.cell_sel_par.cell_resel_hyst = 2; /* 4 dB */
bts->si_common.cell_sel_par.rxlev_acc_min = 0;
bts->si_common.si2quater_neigh_list.arfcn = bts->si_common.data.earfcn_list;
diff --git a/src/osmo-bsc/bts_vty.c b/src/osmo-bsc/bts_vty.c
index b8b9f6c39..3695d2838 100644
--- a/src/osmo-bsc/bts_vty.c
+++ b/src/osmo-bsc/bts_vty.c
@@ -565,6 +565,25 @@ DEFUN_ATTR(cfg_bts_chan_alloc_interf,
return CMD_SUCCESS;
}
+DEFUN_ATTR(cfg_bts_chan_alloc_allow_tch_for_signalling,
+ cfg_bts_chan_alloc_allow_tch_for_signalling_cmd,
+ "channel allocator allow-tch-for-signalling (0|1)",
+ "Channel Allocator\n" "Channel Allocator\n"
+ "Configure whether TCH/H or TCH/F channels can be used to serve non-call-related signalling if SDCCHs are exhausted\n"
+ "Forbid use of TCH for non-call-related signalling purposes\n"
+ "Allow use of TCH for non-call-related signalling purposes (default)\n",
+ CMD_ATTR_IMMEDIATE)
+{
+ struct gsm_bts *bts = vty->index;
+
+ if (!strcmp(argv[0], "0"))
+ bts->chan_alloc_allow_tch_for_signalling = false;
+ else
+ bts->chan_alloc_allow_tch_for_signalling = true;
+
+ return CMD_SUCCESS;
+}
+
#define RACH_STR "Random Access Control Channel\n"
DEFUN_USRATTR(cfg_bts_rach_tx_integer,
@@ -3736,6 +3755,8 @@ static void config_write_bts_single(struct vty *vty, struct gsm_bts *bts)
VTY_NEWLINE);
if (bts->chan_alloc_avoid_interf)
vty_out(vty, " channel allocator avoid-interference 1%s", VTY_NEWLINE);
+ if (!bts->chan_alloc_allow_tch_for_signalling)
+ vty_out(vty, " channel allocator allow-tch-for-signalling 0%s", VTY_NEWLINE);
vty_out(vty, " rach tx integer %u%s",
bts->si_common.rach_control.tx_integer, VTY_NEWLINE);
vty_out(vty, " rach max transmission %u%s",
@@ -4018,6 +4039,7 @@ int bts_vty_init(void)
install_element(BTS_NODE, &cfg_bts_oml_e1_tei_cmd);
install_element(BTS_NODE, &cfg_bts_challoc_cmd);
install_element(BTS_NODE, &cfg_bts_chan_alloc_interf_cmd);
+ install_element(BTS_NODE, &cfg_bts_chan_alloc_allow_tch_for_signalling_cmd);
install_element(BTS_NODE, &cfg_bts_rach_tx_integer_cmd);
install_element(BTS_NODE, &cfg_bts_rach_max_trans_cmd);
install_element(BTS_NODE, &cfg_bts_rach_max_delay_cmd);
diff --git a/tests/osmo-bsc.vty b/tests/osmo-bsc.vty
index 1d859c3f9..3bc27073a 100644
--- a/tests/osmo-bsc.vty
+++ b/tests/osmo-bsc.vty
@@ -163,14 +163,19 @@ OsmoBSC(config-net-bts)# channel ?
allocator Channel Allocator
OsmoBSC(config-net-bts)# channel allocator ?
- ascending Allocate Timeslots and Transceivers in ascending order
- descending Allocate Timeslots and Transceivers in descending order
- avoid-interference Configure whether reported interference levels from RES IND are used in channel allocation
+ ascending Allocate Timeslots and Transceivers in ascending order
+ descending Allocate Timeslots and Transceivers in descending order
+ avoid-interference Configure whether reported interference levels from RES IND are used in channel allocation
+ allow-tch-for-signalling Configure whether TCH/H or TCH/F channels can be used to serve non-call-related signalling if SDCCHs are exhausted
OsmoBSC(config-net-bts)# channel allocator avoid-interference ?
0 Ignore interference levels (default). Always assign lchans in a deterministic order.
1 In channel allocation, prefer lchans with less interference.
+OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling ?
+ 0 Forbid use of TCH for non-call-related signalling purposes
+ 1 Allow use of TCH for non-call-related signalling purposes (default)
+
OsmoBSC(config-net-bts)# show running-config
... !channel allocator avoid-interference
OsmoBSC(config-net-bts)# channel allocator avoid-interference 1
@@ -184,3 +189,17 @@ OsmoBSC(config-net-bts)# show running-config
OsmoBSC(config-net-bts)# channel allocator avoid-interference 0
OsmoBSC(config-net-bts)# show running-config
... !channel allocator avoid-interference
+
+OsmoBSC(config-net-bts)# show running-config
+... !channel allocator allow-tch-for-signalling
+OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling 0
+OsmoBSC(config-net-bts)# show running-config
+...
+ bts 0
+...
+ channel allocator allow-tch-for-signalling 0
+...
+
+OsmoBSC(config-net-bts)# channel allocator allow-tch-for-signalling 1
+OsmoBSC(config-net-bts)# show running-config
+... !channel allocator allow-tch-for-signalling