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authorHarald Welte <laforge@osmocom.org>2020-12-12 19:02:16 +0100
committerHarald Welte <laforge@osmocom.org>2020-12-12 19:12:18 +0100
commit9e917647aef4679b6fd6eabbe77651bb50b60da8 (patch)
tree252f5697b6bb1621e87df9e8eb0c9560d5f598c0
parent784c59f87e6966ac3dc7e03fad2bbb9ceee8592a (diff)
gbproxy: Implement scaling of BVC flow control in SGSN pool
When there are multiple SGSNs inside a pool, we need to decide how much of the per-BVC capacity advertised by the BSS in its BVC-FLOW-CONTROL we should announce to each of the pool members. A conservative approach would be to advertise 1/num_sgsn, but there may also be use case where over-provisioning (announcing more than an equal share of the capacity) is useful. Hence, let's introduce "pool bvc-flow-control-ratio <1-100>" in order to allow the administrator to decide. Related: OS#4891 Change-Id: Ibe5addf657e7237499ca0205bacfe999ecd1e771
-rw-r--r--doc/manuals/chapters/gbproxy-configuration.adoc26
-rw-r--r--include/osmocom/sgsn/gb_proxy.h5
-rw-r--r--src/gbproxy/gb_proxy.c22
-rw-r--r--src/gbproxy/gb_proxy_vty.c15
4 files changed, 65 insertions, 3 deletions
diff --git a/doc/manuals/chapters/gbproxy-configuration.adoc b/doc/manuals/chapters/gbproxy-configuration.adoc
index 599b3f7b..e61af48b 100644
--- a/doc/manuals/chapters/gbproxy-configuration.adoc
+++ b/doc/manuals/chapters/gbproxy-configuration.adoc
@@ -4,3 +4,29 @@ TBD. Unfortunately this chapter of the manual still needs to be written.
Osmocom has very limited funding and support resources; Feel free to help
us completing this documentation by contributing with code, documentation
or by supporting the developers financially.
+
+
+=== SGSN pool support
+
+In a SGSN pool, osmo-gbproxy is facing the problem of dividing the downlink
+capacity of a cell towards the SGSN. The BSS advertises the per-BVC capacity
+by means of the BSSGP FLOW-CONTROL-BVC messages, but as there are multiple
+SGSN in a pool, they all have to share / divide that total capacity.
+
+By default, osmo-gbproxy advertises the full capacity to _each_ of the SGSN
+pool members, which results in significant over-provisioning and can lead to
+overload situations.
+
+The administrator can configure the _percentage_ of the overall BSS-advertised
+capacity that shall be reported to each pool member SGSN using the
+`pool bvc-flow-control-ratio <1-100>` configuration command.
+
+A setting of 100 means that each pool member is informed of 100% of the
+BSS side capacity.
+
+A setting of 25 means that each pool member is informed of 25% of the
+BSS side capacity. This would make most sense in a set-up with four
+SGSN of equal share.
+
+More complex capacity division schemes are so far not supported by
+osmo-gbproxy.
diff --git a/include/osmocom/sgsn/gb_proxy.h b/include/osmocom/sgsn/gb_proxy.h
index 8892cf4d..200a539e 100644
--- a/include/osmocom/sgsn/gb_proxy.h
+++ b/include/osmocom/sgsn/gb_proxy.h
@@ -52,6 +52,11 @@ struct gbproxy_config {
/* NS instance of libosmogb */
struct gprs_ns2_inst *nsi;
+ struct {
+ /* percentage of BVC flow control advertised to each SGSN in the pool */
+ uint8_t bvc_fc_ratio;
+ } pool;
+
/* Linked list of all BSS side Gb peers */
DECLARE_HASHTABLE(bss_nses, 8);
diff --git a/src/gbproxy/gb_proxy.c b/src/gbproxy/gb_proxy.c
index a976d252..53aecdf0 100644
--- a/src/gbproxy/gb_proxy.c
+++ b/src/gbproxy/gb_proxy.c
@@ -40,6 +40,7 @@
#include <osmocom/gprs/gprs_ns2.h>
#include <osmocom/gprs/gprs_bssgp.h>
+#include <osmocom/gprs/gprs_bssgp2.h>
#include <osmocom/gprs/gprs_bssgp_bss.h>
#include <osmocom/gprs/bssgp_bvc_fsm.h>
@@ -566,15 +567,28 @@ static void bss_ptp_bvc_state_chg_notif(uint16_t nsei, uint16_t bvci, int old_st
/* BVC FSM informs us about BVC-FC PDU receive */
static void bss_ptp_bvc_fc_bvc(uint16_t nsei, uint16_t bvci, const struct bssgp2_flow_ctrl *fc, void *priv)
{
+ struct bssgp2_flow_ctrl fc_reduced;
struct gbproxy_bvc *bss_bvc = priv;
- struct gbproxy_cell *cell = bss_bvc->cell;
+ struct gbproxy_cell *cell;
+ struct gbproxy_config *cfg;
+ OSMO_ASSERT(bss_bvc);
+ OSMO_ASSERT(fc);
+
+ cell = bss_bvc->cell;
if (!cell)
return;
- /* FIXME: actually split the bandwidth among the SGSNs! */
+ cfg = cell->cfg;
+
+ /* reduce / scale according to configuration to make sure we only advertise a fraction
+ * of the capacity to each of the SGSNs in the pool */
+ fc_reduced = *fc;
+ fc_reduced.bucket_size_max = (fc->bucket_size_max * cfg->pool.bvc_fc_ratio) / 100;
+ fc_reduced.bucket_leak_rate = (fc->bucket_leak_rate * cfg->pool.bvc_fc_ratio) / 100;
+ /* we don't modify the per-MS related values as any single MS is only served by one SGSN */
- dispatch_to_all_sgsn_bvc(cell, BSSGP_BVCFSM_E_REQ_FC_BVC, (void *) fc);
+ dispatch_to_all_sgsn_bvc(cell, BSSGP_BVCFSM_E_REQ_FC_BVC, (void *) &fc_reduced);
}
static const struct bssgp_bvc_fsm_ops bss_ptp_bvc_fsm_ops = {
@@ -1270,6 +1284,8 @@ int gbproxy_init_config(struct gbproxy_config *cfg)
{
struct timespec tp;
+ /* by default we advertise 100% of the BSS-side capacity to _each_ SGSN */
+ cfg->pool.bvc_fc_ratio = 100;
hash_init(cfg->bss_nses);
cfg->ctrg = rate_ctr_group_alloc(tall_sgsn_ctx, &global_ctrg_desc, 0);
if (!cfg->ctrg) {
diff --git a/src/gbproxy/gb_proxy_vty.c b/src/gbproxy/gb_proxy_vty.c
index a9db596d..49ec91c9 100644
--- a/src/gbproxy/gb_proxy_vty.c
+++ b/src/gbproxy/gb_proxy_vty.c
@@ -76,6 +76,9 @@ static int config_write_gbproxy(struct vty *vty)
vty_out(vty, "gbproxy%s", VTY_NEWLINE);
+ if (g_cfg->pool.bvc_fc_ratio != 100)
+ vty_out(vty, " pool bvc-flow-control-ratio %u%s", g_cfg->pool.bvc_fc_ratio, VTY_NEWLINE);
+
hash_for_each(g_cfg->sgsn_nses, i, nse, list) {
vty_out(vty, " sgsn nsei %u%s", nse->nsei, VTY_NEWLINE);
}
@@ -134,6 +137,17 @@ free_nothing:
return CMD_WARNING;
}
+DEFUN(cfg_pool_bvc_fc_ratio,
+ cfg_pool_bvc_fc_ratio_cmd,
+ "pool bvc-flow-control-ratio <1-100>",
+ "SGSN Pool related configuration\n"
+ "Ratio of BSS-advertised bucket size + leak rate advertised to each SGSN\n"
+ "Ratio of BSS-advertised bucket size + leak rate advertised to each SGSN (Percent)\n")
+{
+ g_cfg->pool.bvc_fc_ratio = atoi(argv[0]);
+ return CMD_SUCCESS;
+}
+
static void log_set_bvc_filter(struct log_target *target,
const uint16_t *bvci)
{
@@ -315,6 +329,7 @@ int gbproxy_vty_init(void)
install_element(CONFIG_NODE, &cfg_gbproxy_cmd);
install_node(&gbproxy_node, config_write_gbproxy);
install_element(GBPROXY_NODE, &cfg_nsip_sgsn_nsei_cmd);
+ install_element(GBPROXY_NODE, &cfg_pool_bvc_fc_ratio_cmd);
return 0;
}