tbf: Implement delayed release of a downlink TBF
Currently a DL TBF is immediately closed, when the LLC queue is
drained. This will lead to a new DL assignment if data is received
afterwards. In addition, it is not possible to keep the PACCH open
to poll the MS for UL establishment requests there.
GSM 44.060, 9.3.1a suggests to delay the release of an inactive TBF
for some time (max 5s).
This commit mainly changes create_new_bsn() to send LLC dummy
commands as filler if no LLC data is available until keep_open()
returns false. The keep_open() functions returns true unless a
configurable time has passed after the LLC data store drained. By
default, that time is not set which causes keep_open() to always
return false, so that delayed release is effectively disabled.
The following VTY commands are added:
- dl-tbf-idle-time <1-5000> to set the delay in ms
- no dl-tbf-idle-time to disable delayed release
Ticket: #556
Sponsored-by: On-Waves ehf
diff --git a/src/bts.h b/src/bts.h
index e845995..3d74b75 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -133,6 +133,7 @@
uint32_t alloc_algorithm_curst; /* options to customize algorithm */
uint8_t force_two_phase;
uint8_t alpha, gamma;
+ uint32_t dl_tbf_idle_msec; /* hold time for idle DL TBFs */
/* TBF handling, make private or move into TBFController */
/* list of uplink TBFs */
diff --git a/src/pcu_utils.h b/src/pcu_utils.h
new file mode 100644
index 0000000..84c545b
--- /dev/null
+++ b/src/pcu_utils.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2015 by Sysmocom s.f.m.c. GmbH
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+inline int msecs_to_frames(int msecs) {
+ return (msecs * (1024 * 1000 / 4615)) / 1024;
+}
diff --git a/src/pcu_vty.c b/src/pcu_vty.c
index 578a10b..9b597ad 100644
--- a/src/pcu_vty.c
+++ b/src/pcu_vty.c
@@ -105,6 +105,9 @@
vty_out(vty, " two-phase-access%s", VTY_NEWLINE);
vty_out(vty, " alpha %d%s", bts->alpha, VTY_NEWLINE);
vty_out(vty, " gamma %d%s", bts->gamma * 2, VTY_NEWLINE);
+ if (bts->dl_tbf_idle_msec)
+ vty_out(vty, " dl-tbf-idle-time %d%s", bts->dl_tbf_idle_msec,
+ VTY_NEWLINE);
return CMD_SUCCESS;
}
@@ -287,6 +290,31 @@
return CMD_SUCCESS;
}
+#define IDLE_TIME_STR "keep an idle DL TBF alive for the time given\n"
+DEFUN(cfg_pcu_dl_tbf_idle_time,
+ cfg_pcu_dl_tbf_idle_time_cmd,
+ "dl-tbf-idle-time <1-5000>",
+ IDLE_TIME_STR "idle time in msec")
+{
+ struct gprs_rlcmac_bts *bts = bts_main_data();
+
+ bts->dl_tbf_idle_msec = atoi(argv[0]);
+
+ return CMD_SUCCESS;
+}
+
+DEFUN(cfg_pcu_no_dl_tbf_idle_time,
+ cfg_pcu_no_dl_tbf_idle_time_cmd,
+ "no dl-tbf-idle-time",
+ NO_STR IDLE_TIME_STR)
+{
+ struct gprs_rlcmac_bts *bts = bts_main_data();
+
+ bts->dl_tbf_idle_msec = 0;
+
+ return CMD_SUCCESS;
+}
+
DEFUN(show_tbf,
show_tbf_cmd,
"show tbf all",
@@ -343,6 +371,8 @@
install_element(PCU_NODE, &cfg_pcu_fc_interval_cmd);
install_element(PCU_NODE, &cfg_pcu_alpha_cmd);
install_element(PCU_NODE, &cfg_pcu_gamma_cmd);
+ install_element(PCU_NODE, &cfg_pcu_dl_tbf_idle_time_cmd);
+ install_element(PCU_NODE, &cfg_pcu_no_dl_tbf_idle_time_cmd);
install_element(PCU_NODE, &ournode_end_cmd);
install_element_ve(&show_bts_stats_cmd);
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 56804c3..2c7bd94 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -471,6 +471,7 @@
tbf->bts->tbf_dl_created();
tbf->m_last_dl_poll_fn = -1;
+ tbf->m_last_dl_drained_fn = -1;
gettimeofday(&tbf->m_bw.dl_bw_tv, NULL);
gettimeofday(&tbf->m_bw.dl_loss_tv, NULL);
diff --git a/src/tbf.h b/src/tbf.h
index ca5fedf..17ba980 100644
--- a/src/tbf.h
+++ b/src/tbf.h
@@ -326,6 +326,8 @@
bool need_control_ts() const;
bool have_data() const;
int frames_since_last_poll(unsigned fn) const;
+ int frames_since_last_drain(unsigned fn) const;
+ bool keep_open(unsigned fn) const;
bool is_control_ts(uint8_t ts) const {
return ts == control_ts;
@@ -344,6 +346,7 @@
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;
struct {
struct timeval dl_bw_tv; /* timestamp for dl bw calculation */
diff --git a/src/tbf_dl.cpp b/src/tbf_dl.cpp
index 9baa1cd..65b164e 100644
--- a/src/tbf_dl.cpp
+++ b/src/tbf_dl.cpp
@@ -27,6 +27,8 @@
#include <gprs_bssgp_pcu.h>
#include <decoding.h>
+#include "pcu_utils.h"
+
extern "C" {
#include <osmocom/core/msgb.h>
#include <osmocom/core/talloc.h>
@@ -74,6 +76,8 @@
} else if (!have_data()) {
m_llc.put_frame(data, len);
bts->llc_frame_sched();
+ /* it is no longer drained */
+ m_last_dl_drained_fn = -1;
tbf_update_ms_class(this, ms_class);
} else {
/* the TBF exists, so we must write it in the queue
@@ -354,14 +358,19 @@
* space-1 octets */
m_llc.put_dummy_frame(space - 1);
+ /* The data just drained, store the current fn */
+ if (m_last_dl_drained_fn < 0)
+ m_last_dl_drained_fn = fn;
+
/* It is not clear, when the next real data will
* arrive, so request a DL ack/nack now */
request_dl_ack();
LOGP(DRLCMACDL, LOGL_DEBUG,
"-- Empty chunk, "
- "added LLC dummy command of size %d\n",
- m_llc.frame_length());
+ "added LLC dummy command of size %d, "
+ "drained_since=%d\n",
+ m_llc.frame_length(), frames_since_last_drain(fn));
}
chunk = m_llc.chunk_size();
@@ -380,7 +389,8 @@
break;
}
/* if FINAL chunk would fit precisely in space left */
- if (chunk == space && llist_empty(&m_llc.queue)) {
+ if (chunk == space && llist_empty(&m_llc.queue) && !keep_open(fn))
+ {
LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d "
"would exactly fit into space (%d): because "
"this is a final block, we don't add length "
@@ -424,6 +434,7 @@
/* return data block as message */
break;
}
+
LOGP(DRLCMACDL, LOGL_DEBUG, "-- Chunk with length %d is less "
"than remaining space (%d): add length header to "
"to delimit LLC frame\n", chunk, space);
@@ -456,17 +467,19 @@
m_llc.put_frame(msg->data, msg->len);
bts->llc_frame_sched();
msgb_free(msg);
+ m_last_dl_drained_fn = -1;
}
/* if we have more data and we have space left */
- if (space > 0 && m_llc.frame_length()) {
+ if (space > 0 && (m_llc.frame_length() || keep_open(fn))) {
li->m = 1; /* we indicate more frames to follow */
continue;
}
/* if we don't have more LLC frames */
- if (!m_llc.frame_length()) {
+ if (!m_llc.frame_length() && !keep_open(fn)) {
LOGP(DRLCMACDL, LOGL_DEBUG, "-- Final block, so we "
"done.\n");
li->e = 1; /* we cannot extend */
+
rh->fbi = 1; /* we indicate final block */
request_dl_ack();
set_state(GPRS_RLCMAC_FINISHED);
@@ -771,3 +784,26 @@
return wrapped - 2715648;
}
+int gprs_rlcmac_dl_tbf::frames_since_last_drain(unsigned fn) const
+{
+ unsigned wrapped;
+ if (m_last_dl_drained_fn < 0)
+ return -1;
+
+ wrapped = (fn + 2715648 - m_last_dl_drained_fn) % 2715648;
+ if (wrapped < 2715648/2)
+ return wrapped;
+ else
+ return wrapped - 2715648;
+}
+
+bool gprs_rlcmac_dl_tbf::keep_open(unsigned fn) const
+{
+ int keep_time_frames;
+
+ if (bts_data()->dl_tbf_idle_msec <= 0)
+ return false;
+
+ keep_time_frames = msecs_to_frames(bts_data()->dl_tbf_idle_msec);
+ return frames_since_last_drain(fn) <= keep_time_frames;
+}