Index: simutrans/trunk/network/network_cmd.h
===================================================================
--- simutrans/trunk/network/network_cmd.h	(revision 8342)
+++ simutrans/trunk/network/network_cmd.h	(working copy)
@@ -30,6 +30,7 @@
 	NWC_CHG_PLAYER,
 	NWC_SCENARIO,
 	NWC_SCENARIO_RULES,
+	NWC_STEP,
 	NWC_COUNT
 };
 
Index: simutrans/trunk/network/network_cmd_ingame.cc
===================================================================
--- simutrans/trunk/network/network_cmd_ingame.cc	(revision 8342)
+++ simutrans/trunk/network/network_cmd_ingame.cc	(working copy)
@@ -50,6 +50,7 @@
 		case NWC_SCENARIO:    nwc = new nwc_scenario_t(); break;
 		case NWC_SCENARIO_RULES:
 		                      nwc = new nwc_scenario_rules_t(); break;
+		case NWC_STEP:        nwc = new nwc_step_t(); break;
 		default:
 			dbg->warning("network_command_t::read_from_socket", "received unknown packet id %d", p->get_id());
 	}
Index: simutrans/trunk/network/network_cmd_ingame.h
===================================================================
--- simutrans/trunk/network/network_cmd_ingame.h	(revision 8342)
+++ simutrans/trunk/network/network_cmd_ingame.h	(working copy)
@@ -357,4 +357,18 @@
 	static bool cmp_default_param(const char *d1, const char *d2);
 };
 
+/**
+* nwc_step_t
+* @from-server:
+*		@data contains the current sync_steps of the server
+*       defining the maximum sync_steps a client can advance to.
+*/
+class nwc_step_t : public network_world_command_t {
+public:
+	nwc_step_t() : network_world_command_t(NWC_STEP, 0, 0) { }
+	nwc_step_t(uint32 sync_steps, uint32 map_counter) : network_world_command_t(NWC_STEP, sync_steps, map_counter) {};
+	virtual bool execute(karte_t *) { return true;}
+	virtual const char* get_name() { return "nwc_step_t"; }
+};
+
 #endif
Index: simutrans/trunk/simworld.cc
===================================================================
--- simutrans/trunk/simworld.cc	(revision 8342)
+++ simutrans/trunk/simworld.cc	(working copy)
@@ -1247,6 +1247,7 @@
 	steps = 0;
 	network_frame_count = 0;
 	sync_steps = 0;
+	sync_steps_barrier = sync_steps;
 	map_counter = 0;
 	recalc_average_speed();	// resets timeline
 	koord::locality_factor = settings.get_locality_factor( last_year );
@@ -2001,6 +2002,7 @@
 	idle_time = 0;
 	network_frame_count = 0;
 	sync_steps = 0;
+	sync_steps_barrier = sync_steps;
 
 	for(  uint i=0;  i<MAX_PLAYER_COUNT;  i++  ) {
 		selected_tool[i] = tool_t::general_tool[TOOL_QUERY];
@@ -5209,6 +5211,7 @@
 	steps = 0;
 	network_frame_count = 0;
 	sync_steps = 0;
+	sync_steps_barrier = sync_steps;
 	step_mode = PAUSE_FLAG;
 
 DBG_MESSAGE("karte_t::load()","savegame loading at tick count %i",ticks);
@@ -6234,6 +6237,7 @@
 	if (env_t::networkmode) {
 		time_multiplier = 16;	// reset to normal speed
 		sync_steps = syncsteps_;
+		sync_steps_barrier = sync_steps;
 		steps = sync_steps / settings.get_frames_per_step();
 		network_frame_count = sync_steps % settings.get_frames_per_step();
 		dbg->warning("karte_t::network_game_set_pause", "steps=%d sync_steps=%d pause=%d", steps, sync_steps, pause_);
@@ -6385,6 +6389,14 @@
 					*ms_difference = timediff;
 				}
 			}
+		} else if(  nwc->get_id() == NWC_STEP  ) {
+			// advancing sync_steps_barrier
+			nwc_step_t* nwstep = (nwc_step_t*)nwc;
+
+			uint32 const ssbarrier = nwstep->get_sync_step();
+			if(  sync_steps_barrier < ssbarrier  ) {
+				sync_steps_barrier = ssbarrier;
+			}
 		}
 
 		// check random number generator states
@@ -6525,6 +6537,7 @@
 
 	finish_loop = false;
 	sync_steps = 0;
+	sync_steps_barrier = sync_steps;
 
 	network_frame_count = 0;
 	vector_tpl<uint16>hashes_ok;	// bit set: this client can do something with this player
@@ -6607,7 +6620,8 @@
 		// time for the next step?
 		uint32 time = dr_time();
 		if(  (sint32)next_step_time - (sint32)time <= 0  ) {
-			if(  step_mode&PAUSE_FLAG  ) {
+			if(  step_mode&PAUSE_FLAG ||
+				(env_t::networkmode  &&  !env_t::server  &&  sync_steps >= sync_steps_barrier)  ) {
 				// only update display
 				sync_step( 0, false, true );
 				idle_time = 100;
@@ -6635,6 +6649,7 @@
 						ms_difference -= nst_diff;
 					}
 
+
 					sync_step( (fix_ratio_frame_time*time_multiplier)/16, true, true );
 					if (++network_frame_count == settings.get_frames_per_step()) {
 						// ever fourth frame
@@ -6647,6 +6662,10 @@
 					LCHKLST(sync_steps) = checklist_t(get_random_seed(), halthandle_t::get_next_check(), linehandle_t::get_next_check(), convoihandle_t::get_next_check());
 					// some server side tasks
 					if(  env_t::networkmode  &&  env_t::server  ) {
+						// broadcast step
+						nwc_step_t* nwcstep = new nwc_step_t(sync_steps, map_counter);
+						network_send_all(nwcstep, true);
+
 						// broadcast sync info regularly and when lagged
 						const sint64 timelag = (sint32)dr_time() - (sint32)next_step_time;
 						if(  (network_frame_count == 0  &&  timelag > fix_ratio_frame_time * settings.get_server_frames_ahead() / 2)  ||  (sync_steps % env_t::server_sync_steps_between_checks) == 0  ) {
Index: simutrans/trunk/simworld.h
===================================================================
--- simutrans/trunk/simworld.h	(revision 8342)
+++ simutrans/trunk/simworld.h	(working copy)
@@ -488,6 +488,9 @@
 
 	/// @note variable used in interactive()
 	uint32 sync_steps;
+
+	// The maximum sync_steps that a client can safely advance to.
+	uint32 sync_steps_barrier;
 #define LAST_CHECKLISTS_COUNT 64
 	/// @note variable used in interactive()
 	checklist_t last_checklists[LAST_CHECKLISTS_COUNT];