diff --git a/include/osmocom/msc/transaction.h b/include/osmocom/msc/transaction.h
new file mode 100644
index 0000000..272fb3b
--- /dev/null
+++ b/include/osmocom/msc/transaction.h
@@ -0,0 +1,103 @@
+#ifndef _TRANSACT_H
+#define _TRANSACT_H
+
+#include <osmocom/msc/gsm_data.h>
+#include <osmocom/msc/gsm_subscriber.h>
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/msc/gsm_04_11.h>
+#include <osmocom/msc/mncc.h>
+#include <osmocom/gsm/gsm0411_smc.h>
+#include <osmocom/gsm/gsm0411_smr.h>
+
+enum bridge_state {
+	BRIDGE_STATE_NONE,
+	BRIDGE_STATE_LOOPBACK_PENDING,
+	BRIDGE_STATE_LOOPBACK_ESTABLISHED,
+	BRIDGE_STATE_BRIDGE_PENDING,
+	BRIDGE_STATE_BRIDGE_ESTABLISHED,
+};
+
+/* One transaction */
+struct gsm_trans {
+	/* Entry in list of all transactions */
+	struct llist_head entry;
+
+	/* Back pointer to the network struct */
+	struct gsm_network *net;
+
+	/* The protocol within which we live */
+	uint8_t protocol;
+
+	/* The current transaction ID */
+	uint8_t transaction_id;
+
+	/* To whom we belong, unique identifier of remote MM entity */
+	struct vlr_subscr *vsub;
+
+	/* The associated connection we are using to transmit messages */
+	struct gsm_subscriber_connection *conn;
+
+	/* reference from MNCC or other application */
+	uint32_t callref;
+
+	/* if traffic channel receive was requested */
+	int tch_recv;
+
+	/* is thats one paging? */
+	struct subscr_request *paging_request;
+
+	/* bearer capabilities (rate and codec) */
+	struct gsm_mncc_bearer_cap bearer_cap;
+
+	/* status of the assignment, true when done */
+	bool assignment_done;
+
+	/* if true, TCH_RTP_CREATE is sent after the
+	 * assignment is done */
+	bool tch_rtp_create;
+
+	union {
+		struct {
+
+			/* current call state */
+			int state;
+
+			/* current timer and message queue */
+			int Tcurrent;		/* current CC timer */
+			int T308_second;	/* used to send release again */
+			struct osmo_timer_list timer;
+			struct gsm_mncc msg;	/* stores setup/disconnect/release message */
+		} cc;
+		struct {
+			struct gsm411_smc_inst smc_inst;
+			struct gsm411_smr_inst smr_inst;
+
+			struct gsm_sms *sms;
+		} sms;
+	};
+
+	struct {
+		struct gsm_trans *peer;
+		enum bridge_state state;
+	} bridge;
+};
+
+
+
+struct gsm_trans *trans_find_by_id(struct gsm_subscriber_connection *conn,
+				   uint8_t proto, uint8_t trans_id);
+struct gsm_trans *trans_find_by_callref(struct gsm_network *net,
+					uint32_t callref);
+
+struct gsm_trans *trans_alloc(struct gsm_network *net,
+			      struct vlr_subscr *vsub,
+			      uint8_t protocol, uint8_t trans_id,
+			      uint32_t callref);
+void trans_free(struct gsm_trans *trans);
+
+int trans_assign_trans_id(struct gsm_network *net, struct vlr_subscr *vsub,
+			  uint8_t protocol, uint8_t ti_flag);
+struct gsm_trans *trans_has_conn(const struct gsm_subscriber_connection *conn);
+void trans_conn_closed(struct gsm_subscriber_connection *conn);
+
+#endif