diff --git a/core/environment.c b/core/environment.c
index c0715e5e1..a9e10e9f4 100644
--- a/core/environment.c
+++ b/core/environment.c
@@ -106,11 +106,11 @@ static void environment_init_modes(environment_t* env, int num_modes, int num_st
  * @brief Initialize the federation-specific parts of the environment struct.
  */
 static void environment_init_federated(environment_t* env, int num_is_present_fields) {
-// #ifdef FEDERATED_CENTRALIZED
+#ifdef FEDERATED_NDT_ENABLED
     // FIXME: Create a queue saving tags instead of events. For now, ndt_q stores 
     // dummy events.
     env->ndt_q = pqueue_tag_init(10);
-// #endif
+#endif // FEDERATED_NDT_ENABLED
 #ifdef FEDERATED_DECENTRALIZED
     env->_lf_intended_tag_fields = (tag_t**) calloc(num_is_present_fields, sizeof(tag_t*));
     LF_ASSERT(env->_lf_intended_tag_fields, "Out of memory");
@@ -170,7 +170,9 @@ void environment_free(environment_t* env) {
     pqueue_free(env->event_q);
     pqueue_free(env->recycle_q);
     pqueue_free(env->next_q);
+    #ifdef FEDERATED_NDT_ENABLED
     pqueue_tag_free(env->ndt_q);
+    #endif // FEDERATED_NDT_ENABLED
 
     environment_free_threaded(env);
     environment_free_single_threaded(env);
diff --git a/core/federated/RTI/main.c b/core/federated/RTI/main.c
index 941590285..bfe68ec37 100644
--- a/core/federated/RTI/main.c
+++ b/core/federated/RTI/main.c
@@ -99,6 +99,8 @@ void usage(int argc, const char* argv[]) {
     lf_print("          clock sync attempt (default is 10). Applies to 'init' and 'on'.\n");
     lf_print("  -a, --auth Turn on HMAC authentication options.\n");
     lf_print("  -t, --tracing Turn on tracing.\n");
+    lf_print("  -v, --version The minimum required version of Lingua Franca.");
+    lf_print("      --ndt Turn on ndt optimization.\n");
 
     lf_print("Command given:");
     for (int i = 0; i < argc; i++) {
@@ -170,8 +172,11 @@ int process_clock_sync_args(int argc, const char* argv[]) {
 }
 
 int process_args(int argc, const char* argv[]) {
-    for (int i = 1; i < argc; i++) {
-        if (strcmp(argv[i], "-i") == 0 || strcmp(argv[i], "--id") == 0) {
+    for (int i = 1; i < argc; i++) { 
+        if (strcmp(argv[i], "-v") == 0 || strcmp(argv[i], "--version") == 0) {
+            lf_print("%s", version_info);
+            return 0;
+        } else if (strcmp(argv[i], "-i") == 0 || strcmp(argv[i], "--id") == 0) {
             if (argc < i + 2) {
                 lf_print_error("--id needs a string argument.");
                 usage(argc, argv);
@@ -232,6 +237,8 @@ int process_args(int argc, const char* argv[]) {
             rti.authentication_enabled = true;
         } else if (strcmp(argv[i], "-t") == 0 || strcmp(argv[i], "--tracing") == 0) {
             rti.base.tracing_enabled = true;
+        } else if (strcmp(argv[i], "--ndt" == 0)) {
+            rti.ndt_enabled = true;
         } else if (strcmp(argv[i], " ") == 0) {
             // Tolerate spaces
             continue;
diff --git a/core/federated/RTI/rti_remote.c b/core/federated/RTI/rti_remote.c
index 1961deac1..8e0352ba6 100644
--- a/core/federated/RTI/rti_remote.c
+++ b/core/federated/RTI/rti_remote.c
@@ -335,6 +335,9 @@ void determine_the_ndt_condition() {
 }
 
 void send_upstream_next_downstream_tag(federate_info_t* fed, tag_t next_event_tag) {
+    if (!rti_remote->ndt_enabled) {
+        return;
+    }
     // The RTI receives next_event_tag from the federated fed. 
     // It has to send NDT messages to the upstream federates of fed
     // if the LTC message from an upstream federate is ealrier than the next_event_tag.
@@ -1330,6 +1333,10 @@ int receive_set_up_information(int socket_id, uint16_t fed_id) {
     bool waiting_physical_action_information = true;
     bool waiting_udp_message_and_set_up_clock_sync = true;
 
+    if (!rti_remote->ndt_enabled) {
+        waiting_physical_action_information = false;
+    }
+
     // Buffer for incoming messages.
     // This does not constrain the message size because messages
     // are forwarded piece by piece.
@@ -1794,6 +1801,7 @@ void initialize_RTI(rti_remote_t *rti){
     rti_remote->clock_sync_period_ns = MSEC(10);
     rti_remote->clock_sync_exchanges_per_interval = 10;
     rti_remote->authentication_enabled = false;
+    rti_remote->ndt_enabled = false;
     rti_remote->base.tracing_enabled = false;
     rti_remote->stop_in_progress = false;
 }
diff --git a/core/federated/RTI/rti_remote.h b/core/federated/RTI/rti_remote.h
index 55753fde2..bfe4370bf 100644
--- a/core/federated/RTI/rti_remote.h
+++ b/core/federated/RTI/rti_remote.h
@@ -35,7 +35,7 @@
 /////////////////////////////////////////////
 //// Data structures
 
-static char version_info[] = "0.5.0"; // Simply use Lingua Franca version name now.
+static char version_info[] = "0.5.0"; // Simply use Lingua Franca version name for now.
 
 typedef enum socket_type_t {
     TCP,
@@ -163,6 +163,11 @@ typedef struct rti_remote_t {
      */
     bool authentication_enabled;
 
+    /**
+     * Boolean indicating that NDT message is enabled.
+    */
+    bool ndt_enabled;
+
     /**
      * Boolean indicating that a stop request is already in progress.
      */
diff --git a/core/federated/federate.c b/core/federated/federate.c
index 77ef59005..60b9588a9 100644
--- a/core/federated/federate.c
+++ b/core/federated/federate.c
@@ -67,7 +67,9 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <openssl/rand.h> // For secure random number generation.
 #include <openssl/hmac.h> // For HMAC-based authentication of federates.
 #endif
+#ifdef FEDERATED_NDT_ENABLED
 #include "pqueue_tag.h"
+#endif // FEDERATED_NDT_ENABLED
 
 // Global variables defined in tag.c:
 extern instant_t _lf_last_reported_unadjusted_physical_time_ns;
@@ -423,12 +425,14 @@ int send_timed_message(environment_t* env,
     }
 
     // Insert the intended tag into the ndt_q to send LTC to the RTI quickly.
+#ifdef FEDERATED_NDT_ENABLED
     if (pqueue_tag_size(env->ndt_q) != 0) {
         // FIXME: If the RTI changes the use of NDTs dynamically, merely checking the size
         // is not enough to know whether this federate using the NDT optimization or not.
         LF_PRINT_DEBUG("Insert NDT at the intended to send LTC and NET quickly.");
         pqueue_tag_insert_if_no_match(env->ndt_q, current_message_intended_tag);
     }
+#endif // FEDERATED_NDT_ENABLED
 
     // Trace the event when tracing is enabled
     if (message_type == MSG_TYPE_TAGGED_MESSAGE) {
@@ -1153,6 +1157,7 @@ void connect_to_rti(const char* hostname, int port) {
                 // @see MSG_TYPE_NEIGHBOR_STRUCTURE in net_common.h
                 send_neighbor_structure_to_RTI(_fed.socket_TCP_RTI);
 
+#ifdef FEDERATED_NDT_ENABLED
                 // Send whether this federate has a physical action to the RTI.
                 uint16_t has_physical_action = _fed.min_delay_from_physical_action_to_federate_output != NEVER;
                 unsigned char physical_action_message_buffer[1 + sizeof(uint16_t)];
@@ -1160,6 +1165,7 @@ void connect_to_rti(const char* hostname, int port) {
                 encode_uint16(has_physical_action, &(physical_action_message_buffer[1]));
                 write_to_socket_errexit(_fed.socket_TCP_RTI, 1 + sizeof(uint16_t), physical_action_message_buffer,
                     "Failed to send physical action info to RTI.");
+#endif // FEDERATED_NDT_ENABLED
 
                 uint16_t udp_port = setup_clock_synchronization_with_rti();
 
@@ -1420,6 +1426,7 @@ void send_port_absent_to_federate(environment_t* env, interval_t additional_dela
     
     // FIXME: If port absent messages are not used when there is no zero-delay cycle,
     // This part is not needed as we don't apply the NDT optimization for cycles.
+#ifdef FEDERATED_NDT_ENABLED
     if (pqueue_tag_size(env->ndt_q) != 0 ) {
         // FIXME: If the RTI changes the use of NDTs dynamically, merely checking the size
         // is not enough to know whether this federate using the NDT optimization or not.
@@ -1433,6 +1440,7 @@ void send_port_absent_to_federate(environment_t* env, interval_t additional_dela
             return;
         }
     }
+#endif // FEDERATED_NDT_ENABLED
 
     // Construct the message
     size_t message_length = 1 + sizeof(port_ID) + sizeof(fed_ID) + sizeof(instant_t) + sizeof(microstep_t);
@@ -1948,6 +1956,7 @@ void _lf_logical_tag_complete(tag_t tag_to_send) {
     environment_t *env;
     _lf_get_environments(&env);
     bool need_to_send_LTC = true;
+#ifdef FEDERATED_NDT_ENABLED
     if (pqueue_tag_size(env->ndt_q) != 0 ) {
         // FIXME: If the RTI changes the use of NDTs dynamically, merely checking the size
         // is not enough to know whether this federate using the NDT optimization or not.
@@ -1961,6 +1970,7 @@ void _lf_logical_tag_complete(tag_t tag_to_send) {
             need_to_send_LTC = false;
         }
     }
+#endif // FEDERATED_NDT_ENABLED
     if (need_to_send_LTC) {
         LF_PRINT_LOG("Sending Logical Tag Complete (LTC) " PRINTF_TAG " to the RTI.",
             tag_to_send.time - start_time,
@@ -2391,6 +2401,7 @@ void handle_stop_request_message() {
     lf_mutex_unlock(&outbound_socket_mutex);
 }
 
+#ifdef FEDERATED_NDT_ENABLED
 /**
  * Handle a MSG_TYPE_NEXT_DOWNSTREAM_MESSAGE from the RTI
  * 
@@ -2425,6 +2436,7 @@ void handle_next_downstream_tag() {
         pqueue_tag_insert_if_no_match(env->ndt_q, env->current_tag);
     }
 }
+#endif // FEDERATED_NDT_ENABLED
 
 /**
  * Close sockets used to communicate with other federates, if they are open,
@@ -2643,9 +2655,11 @@ void* listen_to_rti_TCP(void* args) {
             case MSG_TYPE_PORT_ABSENT:
                 handle_port_absent_message(_fed.socket_TCP_RTI, -1);
                 break;
+#ifdef FEDERATED_NDT_ENABLED
             case MSG_TYPE_NEXT_DOWNSTREAM_TAG:
                 handle_next_downstream_tag();
                 break;
+#endif // FEDERATED_NDT_ENABLED
             case MSG_TYPE_CLOCK_SYNC_T1:
             case MSG_TYPE_CLOCK_SYNC_T4:
                 lf_print_error("Federate %d received unexpected clock sync message from RTI on TCP socket.",
@@ -2838,6 +2852,7 @@ tag_t _lf_send_next_event_tag(environment_t* env, tag_t tag, bool wait_for_reply
             // If there is no downstream events that require the NET of the current tag,
             // do not send the NET.
             bool need_to_send_NET = true;
+#ifdef FEDERATED_NDT_ENABLED
             if (pqueue_tag_size(env->ndt_q) != 0 ) {
                 // FIXME: If the RTI changes the use of NDTs dynamically, merely checking the size
                 // is not enough to know whether this federate using the NDT optimization or not.
@@ -2851,6 +2866,7 @@ tag_t _lf_send_next_event_tag(environment_t* env, tag_t tag, bool wait_for_reply
                     need_to_send_NET = false;
                 }
             }
+#endif // FEDERATED_NDT_ENABLED
             if (need_to_send_NET) {
                 _lf_send_tag(MSG_TYPE_NEXT_EVENT_TAG, tag, wait_for_reply);
                 _fed.last_sent_NET = tag;
diff --git a/core/reactor_common.c b/core/reactor_common.c
index 0f45b6103..111cab93a 100644
--- a/core/reactor_common.c
+++ b/core/reactor_common.c
@@ -293,7 +293,7 @@ void _lf_start_time_step(environment_t *env) {
         }
     }
 
-// #ifdef FEDERATED_CENTRALIZED
+#ifdef FEDERATED_NDT_ENABLED
     while (pqueue_tag_size(env->ndt_q) != 0 
     && lf_tag_compare(pqueue_tag_peek(env->ndt_q)->tag, env->current_tag) < 0) {
         // Remove elements of ndt_q with tag less than the current tag.
@@ -302,7 +302,7 @@ void _lf_start_time_step(environment_t *env) {
         tag_to_remove.time - start_time, tag_to_remove.microstep,
         env->current_tag.time - start_time, env->current_tag.microstep);
     }
-// #endif
+#endif
 #ifdef FEDERATED_DECENTRALIZED
     for (int i = 0; i < env->is_present_fields_size; i++) {
         // FIXME: For now, an intended tag of (NEVER, 0)
diff --git a/include/core/environment.h b/include/core/environment.h
index 9684cb057..717c1b4ff 100644
--- a/include/core/environment.h
+++ b/include/core/environment.h
@@ -107,9 +107,9 @@ typedef struct environment_t {
     tag_t** _lf_intended_tag_fields;
     int _lf_intended_tag_fields_size;
 #endif // FEDERATED
-// #ifdef FEDERATED_CENTRALIZED
+#ifdef FEDERATED_NDT_ENABLED
     pqueue_tag_t* ndt_q;
-// #endif // FEDERATED_CENTRALIZED
+#endif // FEDERATED_NDT_ENABLED
 #ifdef LF_ENCLAVES // TODO: Consider dropping #ifdef
     enclave_info_t *enclave_info;
 #endif