diff --git a/src/emuvim/api/zerorpc/network.py b/src/emuvim/api/zerorpc/network.py
index f232166..a64b09e 100644
--- a/src/emuvim/api/zerorpc/network.py
+++ b/src/emuvim/api/zerorpc/network.py
@@ -64,37 +64,47 @@
     def __init__(self, net):
         self.net = net
 
-    def network_action_start(self, vnf_src_name, vnf_dst_name):
+    def network_action_start(self, vnf_src_name, vnf_dst_name, vnf_src_interface=None, vnf_dst_interface=None):
         # call DCNetwork method, not really datacenter specific API for now...
         # provided dc name needs to be part of API endpoint
         # no check if vnfs are really connected to this datacenter...
         logging.debug("RPC CALL: network chain start")
         try:
             c = self.net.setChain(
-                vnf_src_name, vnf_dst_name)
+                vnf_src_name, vnf_dst_name, vnf_src_interface, vnf_dst_interface)
             return str(c)
         except Exception as ex:
             logging.exception("RPC error.")
             return ex.message
 
-    def network_action_stop(self, vnf_src_name, vnf_dst_name):
+    def network_action_stop(self, vnf_src_name, vnf_dst_name, vnf_src_interface=None, vnf_dst_interface=None):
         # call DCNetwork method, not really datacenter specific API for now...
         # provided dc name needs to be part of API endpoint
         # no check if vnfs are really connected to this datacenter...
         logging.debug("RPC CALL: network chain stop")
         try:
             c = self.net.setChain(
-                vnf_src_name, vnf_dst_name, cmd='del-flows')
+                vnf_src_name, vnf_dst_name, vnf_src_interface, vnf_dst_interface, cmd='del-flows')
+            return c
+        except Exception as ex:
+            logging.exception("RPC error.")
+            return ex.message
+
+    # setup the rate measurement for a vnf interface
+    def monitor_setup_rate_measurement(self, vnf_name, vnf_interface, direction, metric):
+        logging.debug("RPC CALL: get rate")
+        try:
+            c = self.net.monitor_agent.setup_rate_measurement(vnf_name, vnf_interface, direction, metric)
             return c
         except Exception as ex:
             logging.exception("RPC error.")
             return ex.message
 
     # get egress(default) or ingress rate of a vnf
-    def monitor_get_rate(self, vnf_name, direction):
+    def monitor_get_rate(self, vnf_name, vnf_interface, direction, metric):
         logging.debug("RPC CALL: get rate")
         try:
-            c = self.net.monitor_agent.get_rate(vnf_name, direction)
+            c = self.net.monitor_agent.get_rate(vnf_name, vnf_interface, direction, metric)
             return c
         except Exception as ex:
             logging.exception("RPC error.")
diff --git a/src/emuvim/cli/monitor.py b/src/emuvim/cli/monitor.py
index 2caca2c..0c3c515 100755
--- a/src/emuvim/cli/monitor.py
+++ b/src/emuvim/cli/monitor.py
@@ -29,13 +29,33 @@
             print "Command not implemented."
 
     def get_rate(self, args):
+        vnf_name = self._parse_vnf_name(args.get("vnf_name"))
+        vnf_interface = self._parse_vnf_interface(args.get("vnf_name"))
+        self.c.monitor_setup_rate_measurement(
+            vnf_name,
+            vnf_interface,
+            args.get("direction"),
+            args.get("metric"))
         while True:
             r = self.c.monitor_get_rate(
-                args.get("vnf_name"),
-                args.get("direction"))
+                vnf_name,
+                vnf_interface,
+                args.get("direction"),
+                args.get("metric"))
             pp.pprint(r)
             time.sleep(1)
 
+    def _parse_vnf_name(self, vnf_name_str):
+        vnf_name = vnf_name_str.split(':')[0]
+        return vnf_name
+
+    def _parse_vnf_interface(self, vnf_name_str):
+        try:
+            vnf_interface = vnf_name_str.split(':')[1]
+        except:
+            vnf_interface = None
+
+        return vnf_interface
 
 parser = argparse.ArgumentParser(description='son-emu network')
 parser.add_argument(
@@ -46,7 +66,10 @@
     help="vnf name to be monitored")
 parser.add_argument(
     "--direction", "-d", dest="direction",
-    help="in (ingress rate) or out (egress rate)")
+    help="rx (ingress rate) or tx (egress rate)")
+parser.add_argument(
+    "--metric", "-m", dest="metric",
+    help="bytes (byte rate), packets (packet rate)")
 
 def main(argv):
     print "This is the son-emu monitor CLI."
diff --git a/src/emuvim/cli/network.py b/src/emuvim/cli/network.py
index 8d4219b..c27da59 100755
--- a/src/emuvim/cli/network.py
+++ b/src/emuvim/cli/network.py
@@ -28,19 +28,43 @@
             print "Command not implemented."
 
     def add(self, args):
+        vnf_src_name = self._parse_vnf_name(args.get("source"))
+        vnf_src_interface = self._parse_vnf_interface(args.get("source"))
+        vnf_dst_name = self._parse_vnf_name(args.get("destination"))
+        vnf_dst_interface = self._parse_vnf_interface(args.get("destination"))
         r = self.c.network_action_start(
             #args.get("datacenter"),
-            args.get("source"),
-            args.get("destination"))
+            vnf_src_name,
+            vnf_dst_name,
+            vnf_src_interface,
+            vnf_dst_interface)
         pp.pprint(r)
 
     def remove(self, args):
+        vnf_src_name = self._parse_vnf_name(args.get("source"))
+        vnf_src_interface = self._parse_vnf_interface(args.get("source"))
+        vnf_dst_name = self._parse_vnf_name(args.get("destination"))
+        vnf_dst_interface = self._parse_vnf_interface(args.get("destination"))
         r = self.c.network_action_stop(
             #args.get("datacenter"),
-            args.get("source"),
-            args.get("destination"))
+            vnf_src_name,
+            vnf_dst_name,
+            vnf_src_interface,
+            vnf_dst_interface)
         pp.pprint(r)
 
+    def _parse_vnf_name(self, vnf_name_str):
+        vnf_name = vnf_name_str.split(':')[0]
+        return vnf_name
+
+    def _parse_vnf_interface(self, vnf_name_str):
+        try:
+            vnf_interface = vnf_name_str.split(':')[1]
+        except:
+            vnf_interface = None
+
+        return vnf_interface
+
 
 parser = argparse.ArgumentParser(description='son-emu network')
 parser.add_argument(
diff --git a/src/emuvim/dcemulator/monitoring.py b/src/emuvim/dcemulator/monitoring.py
index f5da2a1..50393ea 100755
--- a/src/emuvim/dcemulator/monitoring.py
+++ b/src/emuvim/dcemulator/monitoring.py
@@ -21,38 +21,35 @@
 
         self.previous_measurement = 0
         self.previous_monitor_time = 0
+        self.switch_dpid = 0
+        self.metric_key = None
+        self.mon_port = None
 
-    def get_rate(self, vnf_name, direction='tx', metric='packets'):
+    # first set some parameters, before measurement can start
+    def setup_rate_measurement(self, vnf_name, vnf_interface=None, direction='tx', metric='packets'):
         # check if port is specified (vnf:port)
-        try:
-            vnf_interface = vnf_name.split(':')[1]
-        except:
+        if vnf_interface is None:
             # take first interface by default
             connected_sw = self.net.DCNetwork_graph.neighbors(vnf_name)[0]
             link_dict = self.net.DCNetwork_graph[vnf_name][connected_sw]
             vnf_interface = link_dict[0]['src_port_id']
-            # vnf_source_interface = 0
-
-        vnf_name = vnf_name.split(':')[0]
-        # take into account that this is a MultiGraph
-        #mon_port = self.net.DCNetwork_graph[vnf_name][connected_sw][0]['dst_port']
 
         for connected_sw in self.net.DCNetwork_graph.neighbors(vnf_name):
             link_dict = self.net.DCNetwork_graph[vnf_name][connected_sw]
             for link in link_dict:
-                # logging.info("{0},{1}".format(link_dict[link],vnf_source_interface))
+                # logging.info("{0},{1}".format(link_dict[link],vnf_interface))
                 if link_dict[link]['src_port_id'] == vnf_interface:
                     # found the right link and connected switch
                     # logging.info("{0},{1}".format(link_dict[link]['src_port_id'], vnf_source_interface))
-                    #src_sw = connected_sw
-
-                    mon_port = link_dict[link]['dst_port']
+                    self.mon_port = link_dict[link]['dst_port']
                     break
 
         try:
             # default port direction to monitor
             if direction is None:
                 direction = 'tx'
+            if metric is None:
+                metric = 'packets'
 
             vnf_switch = self.net.DCNetwork_graph.neighbors(str(vnf_name))
 
@@ -66,21 +63,31 @@
                 vnf_switch = vnf_switch[0]
             next_node = self.net.getNodeByName(vnf_switch)
 
-            if not isinstance( next_node, OVSSwitch ):
+            if not isinstance(next_node, OVSSwitch):
                 logging.info("vnf: {0} is not connected to switch".format(vnf_name))
                 return
 
+            self.previous_measurement = 0
+            self.previous_monitor_time = 0
 
-            switch_dpid = x = int(str(next_node.dpid),16)
+            #self.switch_dpid = x = int(str(next_node.dpid), 16)
+            self.switch_dpid = int(str(next_node.dpid), 16)
+            self.metric_key = '{0}_{1}'.format(direction, metric)
 
-            # TODO get metric name from arg
-            key = '{0}_{1}'.format(direction, metric)
+        except Exception as ex:
+            logging.exception("get_txrate error.")
+            return ex.message
 
 
-            ret = self.REST_cmd('stats/port', switch_dpid)
+    # call this function repeatedly for streaming measurements
+    def get_rate(self, vnf_name, vnf_interface=None, direction='tx', metric='packets'):
+
+            key = self.metric_key
+
+            ret = self.REST_cmd('stats/port', self.switch_dpid)
             port_stat_dict = ast.literal_eval(ret)
-            for port_stat in port_stat_dict[str(switch_dpid)]:
-                if port_stat['port_no'] == mon_port:
+            for port_stat in port_stat_dict[str(self.switch_dpid)]:
+                if port_stat['port_no'] == self.mon_port:
                     port_uptime = port_stat['duration_sec'] + port_stat['duration_nsec'] * 10 ** (-9)
                     this_measurement = port_stat[key]
 
@@ -89,13 +96,12 @@
                         self.previous_monitor_time = port_uptime
                         # do first measurement
                         time.sleep(1)
-                        byte_rate = self.get_rate(vnf_name,direction)
+                        byte_rate = self.get_rate(vnf_name, vnf_interface, direction, metric)
                         return byte_rate
                     else:
                         time_delta = (port_uptime - self.previous_monitor_time)
                         byte_rate = (this_measurement - self.previous_measurement) / float(time_delta)
                         #logging.info('uptime:{2} delta:{0} rate:{1}'.format(time_delta,byte_rate,port_uptime))
-                        #return byte_rate
 
                     self.previous_measurement = this_measurement
                     self.previous_monitor_time = port_uptime
@@ -103,12 +109,6 @@
 
             return ret
 
-        except Exception as ex:
-            logging.exception("get_txrate error.")
-            return ex.message
-
-
-
     def REST_cmd(self, prefix, dpid):
         url = self.REST_api + '/' + str(prefix) + '/' + str(dpid)
         req = urllib2.Request(url)
diff --git a/src/emuvim/dcemulator/net.py b/src/emuvim/dcemulator/net.py
index 47b4a7e..d6bb5bb 100755
--- a/src/emuvim/dcemulator/net.py
+++ b/src/emuvim/dcemulator/net.py
@@ -184,24 +184,21 @@
         CLI(self)
 
     # to remove chain do setChain( src, dst, cmd='del-flows')
-    def setChain(self, vnf_src_name, vnf_dst_name, cmd='add-flow'):
+    def setChain(self, vnf_src_name, vnf_dst_name, vnf_src_interface=None, vnf_dst_interface=None, cmd='add-flow'):
 
         #check if port is specified (vnf:port)
-        try:
-            vnf_source_interface = vnf_src_name.split(':')[1]
-        except:
+        if vnf_src_interface is None:
             # take first interface by default
             connected_sw = self.DCNetwork_graph.neighbors(vnf_src_name)[0]
             link_dict = self.DCNetwork_graph[vnf_src_name][connected_sw]
-            vnf_source_interface = link_dict[0]['src_port_id']
+            vnf_src_interface = link_dict[0]['src_port_id']
             #vnf_source_interface = 0
 
-        vnf_src_name = vnf_src_name.split(':')[0]
         for connected_sw in self.DCNetwork_graph.neighbors(vnf_src_name):
             link_dict = self.DCNetwork_graph[vnf_src_name][connected_sw]
             for link in link_dict:
                 #logging.info("{0},{1}".format(link_dict[link],vnf_source_interface))
-                if link_dict[link]['src_port_id'] == vnf_source_interface:
+                if link_dict[link]['src_port_id'] == vnf_src_interface:
                     # found the right link and connected switch
                     #logging.info("{0},{1}".format(link_dict[link]['src_port_id'], vnf_source_interface))
                     src_sw = connected_sw
@@ -209,20 +206,18 @@
                     src_sw_inport = link_dict[link]['dst_port']
                     break
 
-        try:
-            vnf_dest_interface = vnf_dst_name.split(':')[1]
-        except:
+        if vnf_dst_interface is None:
             # take first interface by default
             connected_sw = self.DCNetwork_graph.neighbors(vnf_dst_name)[0]
             link_dict = self.DCNetwork_graph[connected_sw][vnf_dst_name]
-            vnf_dest_interface = link_dict[0]['dst_port_id']
+            vnf_dst_interface = link_dict[0]['dst_port_id']
             #vnf_dest_interface = 0
 
         vnf_dst_name = vnf_dst_name.split(':')[0]
         for connected_sw in self.DCNetwork_graph.neighbors(vnf_dst_name):
             link_dict = self.DCNetwork_graph[connected_sw][vnf_dst_name]
             for link in link_dict:
-                if link_dict[link]['dst_port_id'] == vnf_dest_interface:
+                if link_dict[link]['dst_port_id'] == vnf_dst_interface:
                     # found the right link and connected switch
                     dst_sw = connected_sw
                     dst_sw_outport = link_dict[link]['src_port']
@@ -260,6 +255,7 @@
                 logging.info("Next node: {0} is not a switch".format(next_hop))
                 return "Next node: {0} is not a switch".format(next_hop)
             else:
+                # take first link between switches by default
                 index_edge_out = 0
                 switch_outport = self.DCNetwork_graph[current_hop][next_hop][index_edge_out]['src_port']
 
@@ -292,9 +288,10 @@
                 current_node.dpctl(cmd, ofcmd)
                 logging.info("add flow in switch: {0} in_port: {1} out_port: {2}".format(current_node.name, switch_inport,
                                                                                      switch_outport))
-
-            switch_inport = self.DCNetwork_graph[current_hop][next_hop][index_edge_out]['dst_port']
-            current_hop = next_hop
+            # take first link between switches by default
+            if isinstance( next_node, OVSSwitch ):
+                switch_inport = self.DCNetwork_graph[current_hop][next_hop][0]['dst_port']
+                current_hop = next_hop
 
         return "path added between {0} and {1}".format(vnf_src_name, vnf_dst_name)
         #return "destination node: {0} not reached".format(vnf_dst_name)
@@ -311,9 +308,9 @@
         ryu_of_port = '6653'
         ryu_cmd = 'ryu-manager'
         FNULL = open("/tmp/ryu.log", 'w')
-        self.ryu_process = Popen([ryu_cmd, ryu_path, ryu_path2, ryu_option, ryu_of_port], stdout=FNULL, stderr=FNULL)
+        #self.ryu_process = Popen([ryu_cmd, ryu_path, ryu_path2, ryu_option, ryu_of_port], stdout=FNULL, stderr=FNULL)
         # no learning switch
-        #self.ryu_process = Popen([ryu_cmd, ryu_path2, ryu_option, ryu_of_port], stdout=FNULL, stderr=FNULL)
+        self.ryu_process = Popen([ryu_cmd, ryu_path2, ryu_option, ryu_of_port], stdout=FNULL, stderr=FNULL)
         time.sleep(1)
 
     def stopRyu(self):