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laforge gerrit-no-reply at lists.osmocom.orglaforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bsc/+/18778 )
Change subject: MSC pooling: add 'no allow-attach' for MSC off-loading
......................................................................
MSC pooling: add 'no allow-attach' for MSC off-loading
As in 3GPP TS 23.236, to offload an MSC, the BSC must be able to avoid
attaching new subscribers to it:
4.5a.1: "UEs being moved from one CN node are stopped from registering to the
same CN node again by an O&M command in BSCs and RNCs connected to the pool."
Change-Id: I6249201c15d0f6565aca643c21d2375c9ca58584
---
M include/osmocom/bsc/bsc_msc_data.h
M src/osmo-bsc/gsm_08_08.c
M src/osmo-bsc/osmo_bsc_msc.c
M src/osmo-bsc/osmo_bsc_vty.c
M tests/nri_cfg.vty
5 files changed, 55 insertions(+), 1 deletion(-)
Approvals:
Jenkins Builder: Verified
laforge: Looks good to me, approved
pespin: Looks good to me, but someone else must approve
diff --git a/include/osmocom/bsc/bsc_msc_data.h b/include/osmocom/bsc/bsc_msc_data.h
index 6e29bfe..f19b9a0 100644
--- a/include/osmocom/bsc/bsc_msc_data.h
+++ b/include/osmocom/bsc/bsc_msc_data.h
@@ -181,6 +181,7 @@
} mgcp_ipa;
struct osmo_nri_ranges *nri_ranges;
+ bool allow_attach;
};
int osmo_bsc_msc_init(struct bsc_msc_data *msc);
diff --git a/src/osmo-bsc/gsm_08_08.c b/src/osmo-bsc/gsm_08_08.c
index 46ef9af..c002ebb 100644
--- a/src/osmo-bsc/gsm_08_08.c
+++ b/src/osmo-bsc/gsm_08_08.c
@@ -280,7 +280,18 @@
/* Figure out the next round-robin MSC. The MSCs may appear unsorted in net->mscs. Make sure to linearly
* round robin the MSCs by number: pick the lowest msc->nr >= round_robin_next_nr, and also remember the
- * lowest available msc->nr to wrap back to that in case no next MSC is left. */
+ * lowest available msc->nr to wrap back to that in case no next MSC is left.
+ *
+ * MSCs configured with `no allow-attach` do not accept new subscribers and hence must not be picked by
+ * round-robin. Such an MSC still provides service for already attached subscribers: those that
+ * successfully performed IMSI-Attach and have a TMSI with an NRI pointing at that MSC. We only avoid
+ * adding IMSI-Attach of new subscribers. The idea is that the MSC is in a mode of off-loading
+ * subscribers, and the MSC decides when each subscriber is off-loaded, by assigning the NULL-NRI in a
+ * new TMSI (at the next periodical LU). So until the MSC decides to offload, an attached subscriber
+ * remains attached to that MSC and is free to use its services.
+ */
+ if (!msc->allow_attach)
+ continue;
if (!msc_round_robin_first || msc->nr < msc_round_robin_first->nr)
msc_round_robin_first = msc;
if (msc->nr >= round_robin_next_nr
diff --git a/src/osmo-bsc/osmo_bsc_msc.c b/src/osmo-bsc/osmo_bsc_msc.c
index ce07518..157808e 100644
--- a/src/osmo-bsc/osmo_bsc_msc.c
+++ b/src/osmo-bsc/osmo_bsc_msc.c
@@ -230,6 +230,7 @@
msc_data->mgcp_ipa.local_port = 0; /* dynamic */
msc_data->nri_ranges = osmo_nri_ranges_alloc(msc_data);
+ msc_data->allow_attach = true;
return msc_data;
}
diff --git a/src/osmo-bsc/osmo_bsc_vty.c b/src/osmo-bsc/osmo_bsc_vty.c
index c860cfe..5c624dd 100644
--- a/src/osmo-bsc/osmo_bsc_vty.c
+++ b/src/osmo-bsc/osmo_bsc_vty.c
@@ -177,6 +177,9 @@
}
msc_write_nri(vty, msc, false);
+
+ if (!msc->allow_attach)
+ vty_out(vty, " no allow-attach%s", VTY_NEWLINE);
}
static int config_write_msc(struct vty *vty)
@@ -860,6 +863,28 @@
return CMD_SUCCESS;
}
+DEFUN(cfg_msc_allow_attach, cfg_msc_allow_attach_cmd,
+ "allow-attach",
+ "Allow this MSC to attach new subscribers (default).\n")
+{
+ struct bsc_msc_data *msc = bsc_msc_data(vty);
+ msc->allow_attach = true;
+ return CMD_SUCCESS;
+}
+
+DEFUN(cfg_msc_no_allow_attach, cfg_msc_no_allow_attach_cmd,
+ "no allow-attach",
+ NO_STR
+ "Do not assign new subscribers to this MSC."
+ " Useful if an MSC in an MSC pool is configured to off-load subscribers."
+ " The MSC will still be operational for already IMSI-Attached subscribers,"
+ " but the NAS node selection function will skip this MSC for new subscribers\n")
+{
+ struct bsc_msc_data *msc = bsc_msc_data(vty);
+ msc->allow_attach = false;
+ return CMD_SUCCESS;
+}
+
static void msc_write_nri(struct vty *vty, struct bsc_msc_data *msc, bool verbose)
{
struct osmo_nri_range *r;
@@ -963,6 +988,8 @@
install_element(MSC_NODE, &cfg_msc_nri_add_cmd);
install_element(MSC_NODE, &cfg_msc_nri_del_cmd);
install_element(MSC_NODE, &cfg_msc_show_nri_cmd);
+ install_element(MSC_NODE, &cfg_msc_allow_attach_cmd);
+ install_element(MSC_NODE, &cfg_msc_no_allow_attach_cmd);
/* Deprecated: ping time config, kept to support legacy config files. */
install_element(MSC_NODE, &cfg_net_msc_no_ping_time_cmd);
diff --git a/tests/nri_cfg.vty b/tests/nri_cfg.vty
index 680b8ef..8287eab 100644
--- a/tests/nri_cfg.vty
+++ b/tests/nri_cfg.vty
@@ -150,3 +150,17 @@
OsmoBSC(config-msc)# show nri
msc 0
nri add 0 1000
+
+OsmoBSC(config-msc)# show running-config
+... ! no allow-attach
+OsmoBSC(config-msc)# no allow-attach
+OsmoBSC(config-msc)# show running-config
+...
+msc 0
+...
+ nri add 0 1000
+ no allow-attach
+... ! no allow-attach
+OsmoBSC(config-msc)# allow-attach
+OsmoBSC(config-msc)# show running-config
+... ! no allow-attach
--
To view, visit https://gerrit.osmocom.org/c/osmo-bsc/+/18778
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: I6249201c15d0f6565aca643c21d2375c9ca58584
Gerrit-Change-Number: 18778
Gerrit-PatchSet: 6
Gerrit-Owner: neels <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel <dwillmann at sysmocom.de>
Gerrit-Reviewer: dexter <pmaier at sysmocom.de>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: neels <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
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