diff --git a/include/osmocom/msc/msub.h b/include/osmocom/msc/msub.h
new file mode 100644
index 0000000..2418feb
--- /dev/null
+++ b/include/osmocom/msc/msub.h
@@ -0,0 +1,79 @@
+#pragma once
+
+#include <osmocom/msc/debug.h>
+#include <osmocom/msc/msc_roles.h>
+
+struct vlr_subscr;
+struct gsm_network;
+enum gsm48_gsm_cause;
+enum complete_layer3_type;
+enum osmo_gsup_access_network_protocol;
+
+#define VSUB_USE_MSUB "active-conn"
+
+struct msub {
+	struct llist_head entry;
+	struct osmo_fsm_inst *fi;
+
+	struct vlr_subscr *vsub;
+
+	/* role = {MSC_ROLE_A, MSC_ROLE_I, MSC_ROLE_T} */
+	struct osmo_fsm_inst *role[MSC_ROLES_COUNT];
+	struct gsm_network *net;
+};
+
+extern struct llist_head msub_list;
+
+#define LOG_MSUB_CAT_SRC(msub, cat, level, file, line, fmt, args ...) \
+	LOGPSRC(cat, level, file, line, "(%s) " fmt, msub_name(msub), ## args)
+
+#define LOG_MSUB_CAT(msub, cat, level, fmt, args ...) \
+	LOGP(cat, level, "msub(%s) " fmt, msub_name(msub), ## args)
+
+#define LOG_MSUB(msub, level, fmt, args ...) \
+	LOG_MSUB_CAT(msub, DMSC, level, fmt, ## args)
+
+struct msub *msub_alloc(struct gsm_network *net);
+
+#define msub_role_alloc(MSUB, ROLE, FSM, ROLE_STRUCT, RAN) \
+	(ROLE_STRUCT*)_msub_role_alloc(MSUB, ROLE, FSM, sizeof(ROLE_STRUCT), #ROLE_STRUCT ":" #FSM, RAN)
+struct msc_role_common *_msub_role_alloc(struct msub *msub, enum msc_role role, struct osmo_fsm *role_fsm,
+					 size_t struct_size, const char *struct_name, struct ran_infra *ran);
+
+const char *msub_name(const struct msub *msub);
+
+struct msub *msub_for_vsub(const struct vlr_subscr *for_vsub);
+
+void msub_set_role(struct msub *msub, struct osmo_fsm_inst *msc_role);
+void msub_remove_role(struct msub *msub, struct osmo_fsm_inst *fi);
+
+struct msc_a *msub_msc_a(const struct msub *msub);
+struct msc_i *msub_msc_i(const struct msub *msub);
+struct msc_t *msub_msc_t(const struct msub *msub);
+struct ran_conn *msub_ran_conn(const struct msub *msub);
+const char *msub_ran_conn_name(const struct msub *msub);
+
+int msub_set_vsub(struct msub *msub, struct vlr_subscr *vsub);
+struct vlr_subscr *msub_vsub(const struct msub *msub);
+struct gsm_network *msub_net(const struct msub *msub);
+
+int msub_role_to_role_event(struct msub *msub, enum msc_role from_role, enum msc_role to_role);
+#define msub_role_dispatch(MSUB, TO_ROLE, TO_ROLE_EVENT, AN_APDU) \
+	_msub_role_dispatch(MSUB, TO_ROLE, TO_ROLE_EVENT, AN_APDU, __FILE__, __LINE__)
+int _msub_role_dispatch(struct msub *msub, enum msc_role to_role, uint32_t to_role_event, const struct an_apdu *an_apdu,
+			const char *file, int line);
+int msub_tx_an_apdu(struct msub *msub, enum msc_role from_role, enum msc_role to_role, struct an_apdu *an_apdu);
+
+void msub_update_id_from_mi(struct msub *msub, const uint8_t mi[], uint8_t mi_len);
+void msub_update_id(struct msub *msub);
+void msub_update_id_for_vsub(struct vlr_subscr *for_vsub);
+
+void msub_pending_cm_service_req_add(struct msub *msub, enum osmo_cm_service_type type);
+unsigned int msub_pending_cm_service_req_count(struct msub *msub, enum osmo_cm_service_type type);
+void msub_pending_cm_service_req_del(struct msub *msub, enum osmo_cm_service_type type);
+
+void msc_role_forget_conn(struct osmo_fsm_inst *role, struct ran_conn *conn);
+
+struct msgb *msc_role_ran_encode(struct osmo_fsm_inst *role, const struct ran_msg *ran_msg);
+int msc_role_ran_decode(struct osmo_fsm_inst *fi, const struct an_apdu *an_apdu,
+			ran_decode_cb_t decode_cb, void *decode_cb_data);