diff --git a/openair2/LAYER2/NR_MAC_UE/mac_defs.h b/openair2/LAYER2/NR_MAC_UE/mac_defs.h
index d92e0c4fa7..4bcce17ec0 100644
--- a/openair2/LAYER2/NR_MAC_UE/mac_defs.h
+++ b/openair2/LAYER2/NR_MAC_UE/mac_defs.h
@@ -167,6 +167,7 @@ typedef enum {
 
 typedef enum {
   GO_TO_IDLE,
+  T300_EXPIRY,
   RE_ESTABLISHMENT
 } NR_UE_MAC_reset_cause_t;
 
diff --git a/openair2/RRC/NR_UE/rrc_UE.c b/openair2/RRC/NR_UE/rrc_UE.c
index 4d0af37fbe..78c1579e26 100644
--- a/openair2/RRC/NR_UE/rrc_UE.c
+++ b/openair2/RRC/NR_UE/rrc_UE.c
@@ -143,7 +143,7 @@ static void nr_rrc_ue_process_RadioBearerConfig(NR_UE_RRC_INST_t *ue_rrc,
                                                 rnti_t rnti,
                                                 rrcPerNB_t *rrcNB,
                                                 NR_RadioBearerConfig_t *const radioBearerConfig);
-static void nr_rrc_ue_generate_RRCSetupRequest(rnti_t rnti);
+static void nr_rrc_ue_generate_RRCSetupRequest(NR_UE_RRC_INST_t *rrc, rnti_t rnti);
 static void nr_rrc_ue_generate_rrcReestablishmentComplete(NR_RRCReestablishment_t *rrcReestablishment);
 static void process_lte_nsa_msg(NR_UE_RRC_INST_t *rrc, nsa_msg_t *msg, int msg_len);
 static void nr_rrc_ue_process_rrcReconfiguration(const instance_t instance,
@@ -575,12 +575,12 @@ static int nr_decode_SI(NR_UE_RRC_SI_INFO *SI_info, NR_SystemInformation_t *si)
   return 0;
 }
 
-void nr_rrc_ue_generate_ra_msg(instance_t instance, RA_trigger_t trigger, rnti_t rnti)
+void nr_rrc_ue_generate_ra_msg(NR_UE_RRC_INST_t *rrc, RA_trigger_t trigger, rnti_t rnti)
 {
   switch (trigger) {
     case INITIAL_ACCESS_FROM_RRC_IDLE:
       // After SIB1 is received, prepare RRCConnectionRequest
-      nr_rrc_ue_generate_RRCSetupRequest(rnti);
+      nr_rrc_ue_generate_RRCSetupRequest(rrc, rnti);
       break;
     case RRC_CONNECTION_REESTABLISHMENT:
       AssertFatal(1==0, "ra_trigger not implemented yet!\n");
@@ -609,8 +609,9 @@ void nr_rrc_ue_generate_ra_msg(instance_t instance, RA_trigger_t trigger, rnti_t
   }
 }
 
-static void nr_rrc_ue_generate_RRCSetupRequest(rnti_t rnti)
+static void nr_rrc_ue_generate_RRCSetupRequest(NR_UE_RRC_INST_t *rrc, rnti_t rnti)
 {
+  LOG_D(NR_RRC, "Generation of RRCSetupRequest\n");
   uint8_t rv[6];
   // Get RRCConnectionRequest, fill random for now
   // Generate random byte stream for contention resolution
@@ -626,6 +627,10 @@ static void nr_rrc_ue_generate_RRCSetupRequest(rnti_t rnti)
   uint8_t buf[1024];
   int len = do_RRCSetupRequest(buf, sizeof(buf), rv);
 
+  // start timer T300
+  NR_UE_Timers_Constants_t *tac = &rrc->timers_and_constants;
+  tac->T300_active = true;
+
   /* convention: RNTI for SRB0 is zero, as it changes all the time */
   nr_rlc_srb_recv_sdu(rnti, 0, buf, len);
 }
@@ -1476,7 +1481,7 @@ void *rrc_nrue(void *notUsed)
     break;
     
   case NR_RRC_MAC_MSG3_IND:
-    nr_rrc_ue_generate_ra_msg(instance, INITIAL_ACCESS_FROM_RRC_IDLE, NR_RRC_MAC_MSG3_IND(msg_p).rnti);
+    nr_rrc_ue_generate_ra_msg(rrc, INITIAL_ACCESS_FROM_RRC_IDLE, NR_RRC_MAC_MSG3_IND(msg_p).rnti);
     break;
     
   case NR_RRC_MAC_RA_IND:
@@ -1981,6 +1986,15 @@ void nr_rrc_going_to_IDLE(instance_t instance,
   itti_send_msg_to_task(TASK_NAS_NRUE, instance, msg_p);
 }
 
+void handle_t300_expiry(instance_t instance)
+{
+  // reset MAC, release the MAC configuration
+  NR_UE_MAC_reset_cause_t cause = T300_EXPIRY;
+  nr_rrc_mac_config_req_reset(instance, cause);
+  // TODO handle connEstFailureControl
+  // TODO inform upper layers about the failure to establish the RRC connection
+}
+
 void nr_ue_rrc_timer_trigger(int instance, int frame, int gnb_id)
 {
   MessageDef *message_p;
diff --git a/openair2/RRC/NR_UE/rrc_proto.h b/openair2/RRC/NR_UE/rrc_proto.h
index b9f0155d6d..08db8f6506 100644
--- a/openair2/RRC/NR_UE/rrc_proto.h
+++ b/openair2/RRC/NR_UE/rrc_proto.h
@@ -122,6 +122,7 @@ int get_from_lte_ue_fd();
 void nr_rrc_SI_timers(NR_UE_RRC_SI_INFO *SInfo);
 
 void nr_ue_rrc_timer_trigger(int module_id, int frame, int gnb_id);
+void handle_t300_expiry(instance_t instance);
 
 void reset_rlf_timers_and_constants(NR_UE_Timers_Constants_t *tac);
 void set_default_timers_and_constants(NR_UE_Timers_Constants_t *tac);
diff --git a/openair2/RRC/NR_UE/rrc_timers_and_constants.c b/openair2/RRC/NR_UE/rrc_timers_and_constants.c
index c4a4c20183..5b4823d03d 100644
--- a/openair2/RRC/NR_UE/rrc_timers_and_constants.c
+++ b/openair2/RRC/NR_UE/rrc_timers_and_constants.c
@@ -101,7 +101,15 @@ void nr_rrc_SI_timers(NR_UE_RRC_SI_INFO *SInfo)
 void nr_rrc_handle_timers(NR_UE_RRC_INST_t *rrc, instance_t instance)
 {
   NR_UE_Timers_Constants_t *timers = &rrc->timers_and_constants;
-  // T304
+
+  if (timers->T300_active == true) {
+    timers->T300_cnt += 10;
+    if(timers->T300_cnt >= timers->T300_k) {
+      timers->T300_active = false;
+      timers->T300_cnt = 0;
+      handle_t300_expiry(instance);
+    }
+  }
   if (timers->T304_active == true) {
     timers->T304_cnt += 10;
     if(timers->T304_cnt >= timers->T304_k) {