diff --git a/doc/Makefile.am b/doc/Makefile.am
index 08558e5b5..d68b3f6cb 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -26,6 +26,7 @@ dot: \
 	$(builddir)/handover-intra-bsc-fsm.png \
 	$(builddir)/handover-inter-bsc-out-fsm.png \
 	$(builddir)/handover-inter-bsc-in-fsm.png \
+	$(builddir)/mscpool-attach.png \
 	$(NULL)
 
 $(builddir)/%.png: $(srcdir)/%.msc
diff --git a/doc/mscpool-attach.dot b/doc/mscpool-attach.dot
new file mode 100644
index 000000000..f3d0a524f
--- /dev/null
+++ b/doc/mscpool-attach.dot
@@ -0,0 +1,30 @@
+digraph G {
+	rankdir=LR
+	labelloc=t; label="OsmoBSC MSC-pool conn (re)direction"
+
+	subgraph cluster_msc_usable {
+		style=dotted; label="MSC usable\n(successful BSSMAP RESET)"
+
+		allowed [label="MSC\nallow-attach"]
+		notallowed [label="MSC\nno allow-attach\n(MSC should respond\nwith null-NRI)"]
+	}
+
+	subgraph cluster_msc_unusable {
+		style=dotted; label="MSC unusable\n(no link)"
+		allowed_unusable [label="MSC\nallow-attach"]
+		notallowed_unusable [label="MSC\nno allow-attach"]
+	}
+
+	TMSI_unknown_NRI [label="TMSI, NRI unknown"]
+	TMSI_null_NRI [label="TMSI, null-NRI"]
+	TMSI_known_NRI [label="TMSI, NRI known"]
+
+	IMSI -> allowed
+	TMSI_unknown_NRI -> allowed
+	TMSI_null_NRI -> allowed
+	TMSI_known_NRI -> allowed
+	TMSI_known_NRI -> notallowed
+
+	never [style=dotted]
+	never -> {allowed_unusable, notallowed_unusable} [style=dotted]
+}