TestON/tests/TopoPerfNext/TopoPerfNext.py

#TopoPerfNext
#
#Topology Performance test for ONOS-next
#
#andrew@onlab.us

import time
import sys
import os
import re

class TopoPerfNext:
    def __init__(self):
        self.default = ''

    def CASE1(self, main):
        '''
        ONOS startup sequence
        '''
        import time
    
        cell_name = main.params['ENV']['cellName']

        git_pull = main.params['GIT']['autoPull']
        checkout_branch = main.params['GIT']['checkout']

        ONOS1_ip = main.params['CTRL']['ip1']
        ONOS2_ip = main.params['CTRL']['ip2']
        ONOS3_ip = main.params['CTRL']['ip3']
        MN1_ip = main.params['MN']['ip1']
        BENCH_ip = main.params['BENCH']['ip']

        main.case("Setting up test environment")

        main.step("Creating cell file")
        cell_file_result = main.ONOSbench.create_cell_file(
                BENCH_ip, cell_name, MN1_ip, "onos-core",
                ONOS1_ip, ONOS2_ip, ONOS3_ip)

        main.step("Applying cell file to environment")
        cell_apply_result = main.ONOSbench.set_cell(cell_name)
        verify_cell_result = main.ONOSbench.verify_cell()
        
        main.step("Git checkout and pull "+checkout_branch)
        if git_pull == 'on':
            checkout_result = \
                    main.ONOSbench.git_checkout(checkout_branch)
            pull_result = main.ONOSbench.git_pull()
        else:
            checkout_result = main.TRUE
            pull_result = main.TRUE
            main.log.info("Skipped git checkout and pull")

        main.step("Using mvn clean & install")
        #mvn_result = main.ONOSbench.clean_install()
        mvn_result = main.TRUE

        main.step("Creating ONOS package")
        package_result = main.ONOSbench.onos_package()

        main.step("Installing ONOS package")
        install1_result = main.ONOSbench.onos_install(node=ONOS1_ip)
        install2_result = main.ONOSbench.onos_install(node=ONOS2_ip)
        install3_result = main.ONOSbench.onos_install(node=ONOS3_ip)

        #NOTE: This step may be unnecessary
        #main.step("Starting ONOS service")
        #start_result = main.ONOSbench.onos_start(ONOS1_ip)

        main.step("Set cell for ONOS cli env")
        main.ONOS1cli.set_cell(cell_name)
        main.ONOS2cli.set_cell(cell_name)
        main.ONOS3cli.set_cell(cell_name)

        time.sleep(10)

        main.step("Start onos cli")
        cli1 = main.ONOS1cli.start_onos_cli(ONOS1_ip)
        cli2 = main.ONOS2cli.start_onos_cli(ONOS2_ip)
        cli3 = main.ONOS3cli.start_onos_cli(ONOS3_ip)

        main.step("Enable metrics feature")
        main.ONOS1cli.feature_install("onos-app-metrics-topology")
        main.ONOS2cli.feature_install("onos-app-metrics-topology")
        main.ONOS3cli.feature_install("onos-app-metrics-topology")

        utilities.assert_equals(expect=main.TRUE,
                actual= cell_file_result and cell_apply_result and\
                        verify_cell_result and checkout_result and\
                        pull_result and mvn_result and\
                        install1_result and install2_result and\
                        install3_result,
                onpass="ONOS started successfully",
                onfail="Failed to start ONOS")

    def CASE2(self, main):
        '''
        Assign s1 to ONOS1 and measure latency
        
        There are 4 levels of latency measurements to this test:
        1) End-to-end measurement: Complete end-to-end measurement
           from TCP (SYN/ACK) handshake to Graph change
        2) OFP-to-graph measurement: 'ONOS processing' snippet of
           measurement from OFP Vendor message to Graph change
        3) OFP-to-device measurement: 'ONOS processing without 
           graph change' snippet of measurement from OFP vendor
           message to Device change timestamp
        4) T0-to-device measurement: Measurement that includes
           the switch handshake to devices timestamp without 
           the graph view change. (TCP handshake -> Device 
           change)
        '''
        import time
        import subprocess
        import json
        import requests
        import os

        ONOS1_ip = main.params['CTRL']['ip1']
        ONOS2_ip = main.params['CTRL']['ip2']
        ONOS3_ip = main.params['CTRL']['ip3']
        ONOS_user = main.params['CTRL']['user']

        default_sw_port = main.params['CTRL']['port1']
       
        #Number of iterations of case
        num_iter = main.params['TEST']['numIter']
       
        #Timestamp 'keys' for json metrics output.
        #These are subject to change, hence moved into params
        deviceTimestamp = main.params['JSON']['deviceTimestamp']
        graphTimestamp = main.params['JSON']['graphTimestamp']

        #List of switch add latency collected from
        #all iterations
        latency_end_to_end_list = []
        latency_ofp_to_graph_list = []
        latency_ofp_to_device_list = []
        latency_t0_to_device_list = []

        #Directory/file to store tshark results
        tshark_of_output = "/tmp/tshark_of_topo.txt"
        tshark_tcp_output = "/tmp/tshark_tcp_topo.txt"

        #String to grep in tshark output
        tshark_tcp_string = "TCP 74 "+default_sw_port
        tshark_of_string = "OFP 86 Vendor"
     
        #Initialize assertion to TRUE
        assertion = main.TRUE
        
        main.log.report("Latency of adding one switch")

        for i in range(0, int(num_iter)):
            main.log.info("Starting tshark capture")

            #* TCP [ACK, SYN] is used as t0_a, the
            #  very first "exchange" between ONOS and 
            #  the switch for end-to-end measurement
            #* OFP [Stats Reply] is used for t0_b
            #  the very last OFP message between ONOS
            #  and the switch for ONOS measurement
            main.ONOS1.tshark_grep(tshark_tcp_string,
                    tshark_tcp_output)
            main.ONOS1.tshark_grep(tshark_of_string,
                    tshark_of_output)

            #Wait and ensure tshark is started and 
            #capturing
            time.sleep(10)

            main.log.info("Assigning s1 to controller")

            main.Mininet1.assign_sw_controller(sw="1",
                    ip1=ONOS1_ip, port1=default_sw_port)

            #Wait and ensure switch is assigned
            #before stopping tshark
            time.sleep(30)
   
            main.log.info("Stopping all Tshark processes")
            main.ONOS1.stop_tshark()

            #tshark output is saved in ONOS. Use subprocess
            #to copy over files to TestON for parsing
            main.log.info("Copying over tshark files")
            
            #TCP CAPTURE ****
            #Copy the tshark output from ONOS machine to
            #TestON machine in tshark_tcp_output directory>file
            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_tcp_output+" /tmp/") 
            tcp_file = open(tshark_tcp_output, 'r')
            temp_text = tcp_file.readline()
            temp_text = temp_text.split(" ")

            main.log.info("Object read in from TCP capture: "+
                    str(temp_text))
            if len(temp_text) > 1:
                t0_tcp = float(temp_text[1])*1000.0
            else:
                main.log.error("Tshark output file for TCP"+
                        " returned unexpected results")
                t0_tcp = 0
                assertion = main.FALSE
            
            tcp_file.close()
            #****************

            #OF CAPTURE ****
            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_of_output+" /tmp/")
            of_file = open(tshark_of_output, 'r')
           
            line_ofp = ""
            #Read until last line of file
            while True:
                temp_text = of_file.readline()
                if temp_text !='':
                    line_ofp = temp_text
                else:
                    break 
            obj = line_ofp.split(" ")
            
            main.log.info("Object read in from OFP capture: "+
                    str(line_ofp))
    
            if len(line_ofp) > 1:
                t0_ofp = float(obj[1])*1000.0
            else:
                main.log.error("Tshark output file for OFP"+
                        " returned unexpected results")
                t0_ofp = 0
                assertion = main.FALSE
            
            of_file.close()
            #****************
           
            json_str_1 = main.ONOS1cli.topology_events_metrics()
            json_str_2 = main.ONOS2cli.topology_events_metrics()
            json_str_3 = main.ONOS3cli.topology_events_metrics()

            json_obj_1 = json.loads(json_str_1)
            json_obj_2 = json.loads(json_str_2)
            json_obj_3 = json.loads(json_str_3)

            #Obtain graph timestamp. This timestsamp captures
            #the epoch time at which the topology graph was updated.
            graph_timestamp_1 = \
                    json_obj_1[graphTimestamp]['value']
            graph_timestamp_2 = \
                    json_obj_2[graphTimestamp]['value']
            graph_timestamp_3 = \
                    json_obj_3[graphTimestamp]['value']

            #Obtain device timestamp. This timestamp captures
            #the epoch time at which the device event happened
            device_timestamp_1 = \
                    json_obj_1[deviceTimestamp]['value'] 
            device_timestamp_2 = \
                    json_obj_2[deviceTimestamp]['value'] 
            device_timestamp_3 = \
                    json_obj_3[deviceTimestamp]['value'] 

            #t0 to device processing latency 
            delta_device_1 = int(device_timestamp_1) - int(t0_tcp)
            delta_device_2 = int(device_timestamp_2) - int(t0_tcp)
            delta_device_3 = int(device_timestamp_3) - int(t0_tcp)
        
            #Get average of delta from all instances
            avg_delta_device = \
                    (int(delta_device_1)+\
                     int(delta_device_2)+\
                     int(delta_device_3)) / 3

            #Ensure avg delta meets the threshold before appending
            if avg_delta_device > 0.0 and avg_delta_device < 10000:
                latency_t0_to_device_list.append(avg_delta_device)
            else:
                main.log.info("Results for t0-to-device ignored"+\
                        "due to excess in threshold")

            #t0 to graph processing latency (end-to-end)
            delta_graph_1 = int(graph_timestamp_1) - int(t0_tcp)
            delta_graph_2 = int(graph_timestamp_2) - int(t0_tcp)
            delta_graph_3 = int(graph_timestamp_3) - int(t0_tcp)
        
            #Get average of delta from all instances
            avg_delta_graph = \
                    (int(delta_graph_1)+\
                     int(delta_graph_2)+\
                     int(delta_graph_3)) / 3

            #Ensure avg delta meets the threshold before appending
            if avg_delta_graph > 0.0 and avg_delta_graph < 10000:
                latency_end_to_end_list.append(avg_delta_graph)
            else:
                main.log.info("Results for end-to-end ignored"+\
                        "due to excess in threshold")

            #ofp to graph processing latency (ONOS processing)
            delta_ofp_graph_1 = int(graph_timestamp_1) - int(t0_ofp)
            delta_ofp_graph_2 = int(graph_timestamp_2) - int(t0_ofp)
            delta_ofp_graph_3 = int(graph_timestamp_3) - int(t0_ofp)
            
            avg_delta_ofp_graph = \
                    (int(delta_ofp_graph_1)+\
                     int(delta_ofp_graph_2)+\
                     int(delta_ofp_graph_3)) / 3
            
            if avg_delta_ofp_graph > 0.0 and avg_delta_ofp_graph < 10000:
                latency_ofp_to_graph_list.append(avg_delta_ofp_graph)
            else:
                main.log.info("Results for ofp-to-graph "+\
                        "ignored due to excess in threshold")

            #ofp to device processing latency (ONOS processing)
            delta_ofp_device_1 = float(device_timestamp_1) - float(t0_ofp)
            delta_ofp_device_2 = float(device_timestamp_2) - float(t0_ofp)
            delta_ofp_device_3 = float(device_timestamp_3) - float(t0_ofp)
            
            avg_delta_ofp_device = \
                    (float(delta_ofp_device_1)+\
                     float(delta_ofp_device_2)+\
                     float(delta_ofp_device_3)) / 3.0
            
            #NOTE: ofp - delta measurements are occasionally negative
            #      due to system time misalignment.
            latency_ofp_to_device_list.append(avg_delta_ofp_device)

            #TODO:
            #Fetch logs upon threshold excess

            main.log.info("ONOS1 delta end-to-end: "+
                    str(delta_graph_1) + " ms")
            main.log.info("ONOS2 delta end-to-end: "+
                    str(delta_graph_2) + " ms")
            main.log.info("ONOS3 delta end-to-end: "+
                    str(delta_graph_3) + " ms")

            main.log.info("ONOS1 delta OFP - graph: "+
                    str(delta_ofp_graph_1) + " ms")
            main.log.info("ONOS2 delta OFP - graph: "+
                    str(delta_ofp_graph_2) + " ms")
            main.log.info("ONOS3 delta OFP - graph: "+
                    str(delta_ofp_graph_3) + " ms")
            
            main.log.info("ONOS1 delta device - t0: "+
                    str(delta_device_1) + " ms")
            main.log.info("ONOS2 delta device - t0: "+
                    str(delta_device_2) + " ms")
            main.log.info("ONOS3 delta device - t0: "+
                    str(delta_device_3) + " ms")
          
            #main.log.info("ONOS1 delta OFP - device: "+
            #        str(delta_ofp_device_1) + " ms")
            #main.log.info("ONOS2 delta OFP - device: "+
            #        str(delta_ofp_device_2) + " ms")
            #main.log.info("ONOS3 delta OFP - device: "+
            #        str(delta_ofp_device_3) + " ms")

            main.step("Remove switch from controller")
            main.Mininet1.delete_sw_controller("s1")

            time.sleep(5)

        #END of for loop iteration

        #If there is at least 1 element in each list,
        #pass the test case
        if len(latency_end_to_end_list) > 0 and\
           len(latency_ofp_to_graph_list) > 0 and\
           len(latency_ofp_to_device_list) > 0 and\
           len(latency_t0_to_device_list) > 0:
            assertion = main.TRUE
        elif len(latency_end_to_end_list) == 0:
            #The appending of 0 here is to prevent 
            #the min,max,sum functions from failing 
            #below
            latency_end_to_end_list.append(0)
            assertion = main.FALSE
        elif len(latency_ofp_to_graph_list) == 0:
            latency_ofp_to_graph_list.append(0)
            assertion = main.FALSE
        elif len(latency_ofp_to_device_list) == 0:
            latency_ofp_to_device_list.append(0)
            assertion = main.FALSE
        elif len(latency_t0_to_device_list) == 0:
            latency_t0_to_device_list.append(0)
            assertion = main.FALSE

        #Calculate min, max, avg of latency lists
        latency_end_to_end_max = \
                int(max(latency_end_to_end_list))
        latency_end_to_end_min = \
                int(min(latency_end_to_end_list))
        latency_end_to_end_avg = \
                (int(sum(latency_end_to_end_list)) / \
                 len(latency_end_to_end_list))
   
        latency_ofp_to_graph_max = \
                int(max(latency_ofp_to_graph_list))
        latency_ofp_to_graph_min = \
                int(min(latency_ofp_to_graph_list))
        latency_ofp_to_graph_avg = \
                (int(sum(latency_ofp_to_graph_list)) / \
                 len(latency_ofp_to_graph_list))

        latency_ofp_to_device_max = \
                int(max(latency_ofp_to_device_list))
        latency_ofp_to_device_min = \
                int(min(latency_ofp_to_device_list))
        latency_ofp_to_device_avg = \
                (int(sum(latency_ofp_to_device_list)) / \
                 len(latency_ofp_to_device_list))

        latency_t0_to_device_max = \
                float(max(latency_t0_to_device_list))
        latency_t0_to_device_min = \
                float(min(latency_t0_to_device_list))
        latency_t0_to_device_avg = \
                (float(sum(latency_t0_to_device_list)) / \
                 len(latency_ofp_to_device_list))

        main.log.report("Switch add - End-to-end latency: \n"+\
                "Min: "+str(latency_end_to_end_min)+"\n"+\
                "Max: "+str(latency_end_to_end_max)+"\n"+\
                "Avg: "+str(latency_end_to_end_avg))
        main.log.report("Switch add - OFP-to-Graph latency: \n"+\
                "Min: "+str(latency_ofp_to_graph_min)+"\n"+\
                "Max: "+str(latency_ofp_to_graph_max)+"\n"+\
                "Avg: "+str(latency_ofp_to_graph_avg))
        main.log.report("Switch add - t0-to-Device latency: \n"+\
                "Min: "+str(latency_t0_to_device_min)+"\n"+\
                "Max: "+str(latency_t0_to_device_max)+"\n"+\
                "Avg: "+str(latency_t0_to_device_avg))

        utilities.assert_equals(expect=main.TRUE, actual=assertion,
                onpass="Switch latency test successful",
                onfail="Switch latency test failed")

    def CASE3(self, main):
        '''
        Bring port up / down and measure latency.
        Port enable / disable is simulated by ifconfig up / down
        
        In ONOS-next, we must ensure that the port we are 
        manipulating is connected to another switch with a valid
        connection. Otherwise, graph view will not be updated.
        '''
        import time
        import subprocess
        import os
        import requests
        import json

        ONOS1_ip = main.params['CTRL']['ip1']
        ONOS2_ip = main.params['CTRL']['ip2']
        ONOS3_ip = main.params['CTRL']['ip3']
        ONOS_user = main.params['CTRL']['user']

        default_sw_port = main.params['CTRL']['port1']
      
        assertion = main.TRUE
        #Number of iterations of case
        num_iter = main.params['TEST']['numIter']
       
        #Timestamp 'keys' for json metrics output.
        #These are subject to change, hence moved into params
        deviceTimestamp = main.params['JSON']['deviceTimestamp']
        graphTimestamp = main.params['JSON']['graphTimestamp']

        #NOTE: Some hardcoded variables you may need to configure
        #      besides the params
            
        tshark_port_status = "OFP 130 Port Status"

        tshark_port_up = "/tmp/tshark_port_up.txt"
        tshark_port_down = "/tmp/tshark_port_down.txt"
        interface_config = "s1-eth1"

        main.log.report("Port enable / disable latency")

        main.step("Assign switches s1 and s2 to controller 1")
        main.Mininet1.assign_sw_controller(sw="1",ip1=ONOS1_ip,
                port1=default_sw_port)
        main.Mininet1.assign_sw_controller(sw="2",ip1=ONOS1_ip,
                port1=default_sw_port)

        #Give enough time for metrics to propagate the 
        #assign controller event. Otherwise, these events may
        #carry over to our measurements
        time.sleep(10)

        main.step("Verify switch is assigned correctly")
        result_s1 = main.Mininet1.get_sw_controller(sw="s1")
        result_s2 = main.Mininet1.get_sw_controller(sw="s2")
        if result_s1 == main.FALSE or result_s2 == main.FALSE:
            main.log.info("Switch s1 was not assigned correctly")
            assertion = main.FALSE
        else:
            main.log.info("Switch s1 was assigned correctly")

        port_up_device_to_ofp_list = []
        port_up_graph_to_ofp_list = []
        port_down_device_to_ofp_list = []
        port_down_graph_to_ofp_list = []

        for i in range(0, int(num_iter)):
            main.step("Starting wireshark capture for port status down")
            main.ONOS1.tshark_grep(tshark_port_status,
                    tshark_port_down)
            
            time.sleep(10)

            #Disable interface that is connected to switch 2
            main.step("Disable port: "+interface_config)
            main.Mininet2.handle.sendline("sudo ifconfig "+
                    interface_config+" down")
            main.Mininet2.handle.expect("\$")
            time.sleep(10)

            main.ONOS1.tshark_stop()
            time.sleep(5)
            
            #Copy tshark output file from ONOS to TestON instance
            #/tmp directory
            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_port_down+" /tmp/")

            f_port_down = open(tshark_port_down, 'r')
            #Get first line of port down event from tshark
            f_line = f_port_down.readline()
            obj_down = f_line.split(" ")
            if len(f_line) > 0:
                timestamp_begin_pt_down = int(float(obj_down[1]))*1000
                main.log.info("Port down begin timestamp: "+
                        str(timestamp_begin_pt_down))
            else:
                main.log.info("Tshark output file returned unexpected"+
                        " results: "+str(obj_down))
                timestamp_begin_pt_down = 0
            
            f_port_down.close()

            main.log.info("TEST tshark obj: "+str(obj_down))

            main.step("Obtain t1 by REST call")
            json_str_1 = main.ONOS1cli.topology_events_metrics()
            json_str_2 = main.ONOS2cli.topology_events_metrics()
            json_str_3 = main.ONOS3cli.topology_events_metrics()

            main.log.info("TEST json_str 1: "+str(json_str_1))

            json_obj_1 = json.loads(json_str_1)
            json_obj_2 = json.loads(json_str_2)
            json_obj_3 = json.loads(json_str_3)
           
            time.sleep(5)

            #Obtain graph timestamp. This timestsamp captures
            #the epoch time at which the topology graph was updated.
            graph_timestamp_1 = \
                    json_obj_1[graphTimestamp]['value']
            graph_timestamp_2 = \
                    json_obj_2[graphTimestamp]['value']
            graph_timestamp_3 = \
                    json_obj_3[graphTimestamp]['value']

            #Obtain device timestamp. This timestamp captures
            #the epoch time at which the device event happened
            device_timestamp_1 = \
                    json_obj_1[deviceTimestamp]['value'] 
            device_timestamp_2 = \
                    json_obj_2[deviceTimestamp]['value'] 
            device_timestamp_3 = \
                    json_obj_3[deviceTimestamp]['value'] 

            #Get delta between graph event and OFP 
            pt_down_graph_to_ofp_1 = int(graph_timestamp_1) -\
                    int(timestamp_begin_pt_down)
            pt_down_graph_to_ofp_2 = int(graph_timestamp_2) -\
                    int(timestamp_begin_pt_down)
            pt_down_graph_to_ofp_3 = int(graph_timestamp_3) -\
                    int(timestamp_begin_pt_down)

            #Get delta between device event and OFP
            pt_down_device_to_ofp_1 = int(device_timestamp_1) -\
                    int(timestamp_begin_pt_down)
            pt_down_device_to_ofp_2 = int(device_timestamp_2) -\
                    int(timestamp_begin_pt_down)
            pt_down_device_to_ofp_3 = int(device_timestamp_3) -\
                    int(timestamp_begin_pt_down)
       
            #Caluclate average across clusters
            pt_down_graph_to_ofp_avg =\
                    (int(pt_down_graph_to_ofp_1) +
                     int(pt_down_graph_to_ofp_2) + 
                     int(pt_down_graph_to_ofp_3)) / 3.0
            pt_down_device_to_ofp_avg = \
                    (int(pt_down_device_to_ofp_1) + 
                     int(pt_down_device_to_ofp_2) +
                     int(pt_down_device_to_ofp_3)) / 3.0

            if pt_down_graph_to_ofp_avg > 0.0 and \
                    pt_down_graph_to_ofp_avg < 1000:
                port_down_graph_to_ofp_list.append(
                    pt_down_graph_to_ofp_avg)
                main.log.info("Port down: graph to ofp avg: "+
                    str(pt_down_graph_to_ofp_avg) + " ms")
            else:
                main.log.info("Average port down graph-to-ofp result" +
                        " exceeded the threshold: "+
                        str(pt_down_graph_to_ofp_avg))

            if pt_down_device_to_ofp_avg > 0 and \
                    pt_down_device_to_ofp_avg < 1000:
                port_down_device_to_ofp_list.append(
                    pt_down_device_to_ofp_avg)
                main.log.info("Port down: device to ofp avg: "+
                    str(pt_down_device_to_ofp_avg) + " ms")
            else:
                main.log.info("Average port down device-to-ofp result" +
                        " exceeded the threshold: "+
                        str(pt_down_device_to_ofp_avg))

            #Port up events 
            main.step("Enable port and obtain timestamp")
            main.step("Starting wireshark capture for port status up")
            main.ONOS1.tshark_grep("OFP 130 Port Status", tshark_port_up)
            time.sleep(5)

            main.Mininet2.handle.sendline("sudo ifconfig "+
                    interface_config+" up")
            main.Mininet2.handle.expect("\$")
            time.sleep(10)
            
            main.ONOS1.tshark_stop()

            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_port_up+" /tmp/")

            f_port_up = open(tshark_port_up, 'r')
            f_line = f_port_up.readline()
            obj_up = f_line.split(" ")
            if len(f_line) > 0:
                timestamp_begin_pt_up = int(float(obj_up[1]))*1000
                main.log.info("Port up begin timestamp: "+
                        str(timestamp_begin_pt_up))
            else:
                main.log.info("Tshark output file returned unexpected"+
                        " results.")
                timestamp_begin_pt_up = 0
            
            f_port_up.close()

            main.step("Obtain t1 by REST call")
            json_str_1 = main.ONOS1cli.topology_events_metrics()
            json_str_2 = main.ONOS2cli.topology_events_metrics()
            json_str_3 = main.ONOS3cli.topology_events_metrics()

            json_obj_1 = json.loads(json_str_1)
            json_obj_2 = json.loads(json_str_2)
            json_obj_3 = json.loads(json_str_3)

            #Obtain graph timestamp. This timestsamp captures
            #the epoch time at which the topology graph was updated.
            graph_timestamp_1 = \
                    json_obj_1[graphTimestamp]['value']
            graph_timestamp_2 = \
                    json_obj_2[graphTimestamp]['value']
            graph_timestamp_3 = \
                    json_obj_3[graphTimestamp]['value']

            #Obtain device timestamp. This timestamp captures
            #the epoch time at which the device event happened
            device_timestamp_1 = \
                    json_obj_1[deviceTimestamp]['value'] 
            device_timestamp_2 = \
                    json_obj_2[deviceTimestamp]['value'] 
            device_timestamp_3 = \
                    json_obj_3[deviceTimestamp]['value'] 

            #Get delta between graph event and OFP 
            pt_up_graph_to_ofp_1 = int(graph_timestamp_1) -\
                    int(timestamp_begin_pt_up)
            pt_up_graph_to_ofp_2 = int(graph_timestamp_2) -\
                    int(timestamp_begin_pt_up)
            pt_up_graph_to_ofp_3 = int(graph_timestamp_3) -\
                    int(timestamp_begin_pt_up)

            #Get delta between device event and OFP
            pt_up_device_to_ofp_1 = int(device_timestamp_1) -\
                    int(timestamp_begin_pt_up)
            pt_up_device_to_ofp_2 = int(device_timestamp_2) -\
                    int(timestamp_begin_pt_up)
            pt_up_device_to_ofp_3 = int(device_timestamp_3) -\
                    int(timestamp_begin_pt_up)

            pt_up_graph_to_ofp_avg = \
                    (float(pt_up_graph_to_ofp_1) + 
                     float(pt_up_graph_to_ofp_2) +
                     float(pt_up_graph_to_ofp_3)) / 3

            pt_up_device_to_ofp_avg = \
                    (float(pt_up_device_to_ofp_1) + 
                     float(pt_up_device_to_ofp_2) +
                     float(pt_up_device_to_ofp_3)) / 3

            if pt_up_graph_to_ofp_avg > 0 and \
                    pt_up_graph_to_ofp_avg < 1000:
                port_up_graph_to_ofp_list.append(
                        pt_up_graph_to_ofp_avg)
                main.log.info("Port down: graph to ofp avg: "+
                    str(pt_up_graph_to_ofp_avg) + " ms")
            else:
                main.log.info("Average port up graph-to-ofp result"+
                        " exceeded the threshold: "+
                        str(pt_up_graph_to_ofp_avg))
            
            if pt_up_device_to_ofp_avg > 0 and \
                    pt_up_device_to_ofp_avg < 1000:
                port_up_device_to_ofp_list.append(
                        pt_up_device_to_ofp_avg)
                main.log.info("Port up: device to ofp avg: "+
                    str(pt_up_device_to_ofp_avg) + " ms")
            else:
                main.log.info("Average port up device-to-ofp result"+
                        " exceeded the threshold: "+
                        str(pt_up_device_to_ofp_avg))
            
            #END ITERATION FOR LOOP
        
        #Check all list for latency existence and set assertion
        if (port_down_graph_to_ofp_list and port_down_device_to_ofp_list\
           and port_up_graph_to_ofp_list and port_up_device_to_ofp_list):
            assertion = main.TRUE

        #Calculate and report latency measurements
        port_down_graph_to_ofp_min = min(port_down_graph_to_ofp_list)
        port_down_graph_to_ofp_max = max(port_down_graph_to_ofp_list)
        port_down_graph_to_ofp_avg = \
                (sum(port_down_graph_to_ofp_list) / 
                 len(port_down_graph_to_ofp_list))
        
        main.log.report("Port down graph-to-ofp Min: "+
                str(port_down_graph_to_ofp_min)+" ms  Max: "+
                str(port_down_graph_to_ofp_max)+" ms  Avg: "+
                str(port_down_graph_to_ofp_avg))
        
        port_down_device_to_ofp_min = min(port_down_device_to_ofp_list)
        port_down_device_to_ofp_max = max(port_down_device_to_ofp_list)
        port_down_device_to_ofp_avg = \
                (sum(port_down_device_to_ofp_list) /\
                 len(port_down_device_to_ofp_list))
        
        main.log.report("Port down device-to-ofp Min: "+
                str(port_down_device_to_ofp_min)+" ms  Max: "+
                str(port_down_device_to_ofp_max)+" ms  Avg: "+
                str(port_down_device_to_ofp_avg))
        
        port_up_graph_to_ofp_min = min(port_up_graph_to_ofp_list)
        port_up_graph_to_ofp_max = max(port_up_graph_to_ofp_list)
        port_up_graph_to_ofp_avg = \
                (sum(port_up_graph_to_ofp_list) /\
                 len(port_up_graph_to_ofp_list))
        
        main.log.report("Port up graph-to-ofp Min: "+
                str(port_up_graph_to_ofp_min)+" ms  Max: "+
                str(port_up_graph_to_ofp_max)+" ms  Avg: "+
                str(port_up_graph_to_ofp_avg))
          
        port_up_device_to_ofp_min = min(port_up_device_to_ofp_list)
        port_up_device_to_ofp_max = max(port_up_device_to_ofp_list)
        port_up_device_to_ofp_avg = \
                (sum(port_up_device_to_ofp_list) /\
                 len(port_up_device_to_ofp_list))
        
        main.log.report("Port up device-to-ofp Min: "+
                str(port_up_device_to_ofp_min)+" ms  Max: "+
                str(port_up_device_to_ofp_max)+" ms  Avg: "+
                str(port_up_device_to_ofp_avg))

        utilities.assert_equals(expect=main.TRUE, actual=assertion,
                onpass="Port discovery latency calculation successful",
                onfail="Port discovery test failed")

    def CASE4(self, main):
        '''
        Link down event using loss rate 100%
        
        Important:
            Use a simple 2 switch topology with 1 link between
            the two switches. Ensure that mac addresses of the 
            switches are 1 / 2 respectively
        '''
        import time
        import subprocess
        import os
        import requests
        import json

        ONOS1_ip = main.params['CTRL']['ip1']
        ONOS2_ip = main.params['CTRL']['ip2']
        ONOS3_ip = main.params['CTRL']['ip3']
        ONOS_user = main.params['CTRL']['user']

        default_sw_port = main.params['CTRL']['port1']
       
        #Number of iterations of case
        num_iter = main.params['TEST']['numIter']
       
        #Timestamp 'keys' for json metrics output.
        #These are subject to change, hence moved into params
        deviceTimestamp = main.params['JSON']['deviceTimestamp']
        linkTimestamp = main.params['JSON']['linkTimestamp'] 
        graphTimestamp = main.params['JSON']['graphTimestamp']

        assertion = main.TRUE
        #Link event timestamp to system time list
        link_down_link_to_system_list = []
        link_up_link_to_system_list = []
        #Graph event timestamp to system time list
        link_down_graph_to_system_list = []
        link_up_graph_to_system_list = [] 

        main.log.report("Add / remove link latency between "+
                "two switches")

        main.step("Assign all switches")
        main.Mininet1.assign_sw_controller(sw="1",
                ip1=ONOS1_ip, port1=default_sw_port)
        main.Mininet1.assign_sw_controller(sw="2",
                ip1=ONOS1_ip, port1=default_sw_port)

        main.step("Verifying switch assignment")
        result_s1 = main.Mininet1.get_sw_controller(sw="s1")
        result_s2 = main.Mininet1.get_sw_controller(sw="s2")
          
        #Allow time for events to finish before taking measurements
        time.sleep(10)

        link_down1 = False
        link_down2 = False
        link_down3 = False
        #Start iteration of link event test
        for i in range(0, int(num_iter)):
            main.step("Getting initial system time as t0")
            
            timestamp_link_down_t0 = time.time() * 1000
            #Link down is simulated by 100% loss rate using traffic 
            #control command
            main.Mininet1.handle.sendline(
                    "sh tc qdisc add dev s1-eth1 root netem loss 100%")

            #TODO: Iterate through 'links' command to verify that
            #      link s1 -> s2 went down (loop timeout 30 seconds) 
            #      on all 3 ONOS instances
            main.log.info("Checking ONOS for link update")
            loop_count = 0
            while( not (link_down1 and link_down2 and link_down3)\
                    and loop_count < 30 ):
                json_str1 = main.ONOS1cli.links()
                json_str2 = main.ONOS2cli.links()
                json_str3 = main.ONOS3cli.links()
                
                if not (json_str1 and json_str2 and json_str3):
                    main.log.error("CLI command returned error ")
                    break
                else:
                    json_obj1 = json.loads(json_str1)
                    json_obj2 = json.loads(json_str2)
                    json_obj3 = json.loads(json_str3)
                for obj1 in json_obj1:
                    if '01' not in obj1['src']['device']:
                        link_down1 = True
                        main.log.report("Link down from "+
                                "s1 -> s2 on ONOS1 detected")
                for obj2 in json_obj2:
                    if '01' not in obj2['src']['device']:
                        link_down2 = True
                        main.log.report("Link down from "+
                                "s1 -> s2 on ONOS2 detected")
                for obj3 in json_obj3:
                    if '01' not in obj3['src']['device']:
                        link_down3 = True
                        main.log.report("Link down from "+
                                "s1 -> s2 on ONOS3 detected")
                
                loop_count += 1
                #If CLI doesn't like the continuous requests
                #and exits in this loop, increase the sleep here.
                #Consequently, while loop timeout will increase
                time.sleep(1)
    
            #Give time for metrics measurement to catch up
            #NOTE: May need to be configured more accurately
            time.sleep(10)
            #If we exited the while loop and link down 1,2,3 are still 
            #false, then ONOS has failed to discover link down event
            if not (link_down1 and link_down2 and link_down3):
                main.log.info("Link down discovery failed")
                
                link_down_lat_graph1 = 0
                link_down_lat_graph2 = 0
                link_down_lat_graph3 = 0
                link_down_lat_device1 = 0
                link_down_lat_device2 = 0
                link_down_lat_device3 = 0
                
                assertion = main.FALSE
            else:
                json_topo_metrics_1 =\
                        main.ONOS1cli.topology_events_metrics()
                json_topo_metrics_2 =\
                        main.ONOS2cli.topology_events_metrics()
                json_topo_metrics_3 =\
                        main.ONOS3cli.topology_events_metrics()
                json_topo_metrics_1 = json.loads(json_topo_metrics_1)
                json_topo_metrics_2 = json.loads(json_topo_metrics_2)
                json_topo_metrics_3 = json.loads(json_topo_metrics_3)

                main.log.info("Obtaining graph and device timestamp")
                graph_timestamp_1 = \
                    json_topo_metrics_1[graphTimestamp]['value']
                graph_timestamp_2 = \
                    json_topo_metrics_2[graphTimestamp]['value']
                graph_timestamp_3 = \
                    json_topo_metrics_3[graphTimestamp]['value']

                link_timestamp_1 = \
                    json_topo_metrics_1[linkTimestamp]['value']
                link_timestamp_2 = \
                    json_topo_metrics_2[linkTimestamp]['value']
                link_timestamp_3 = \
                    json_topo_metrics_3[linkTimestamp]['value']

                if graph_timestamp_1 and graph_timestamp_2 and\
                        graph_timestamp_3 and link_timestamp_1 and\
                        link_timestamp_2 and link_timestamp_3:
                    link_down_lat_graph1 = int(graph_timestamp_1) -\
                            timestamp_link_down_t0
                    link_down_lat_graph2 = int(graph_timestamp_2) -\
                            timestamp_link_down_t0
                    link_down_lat_graph3 = int(graph_timestamp_3) -\
                            timestamp_link_down_t0
                
                    link_down_lat_link1 = int(link_timestamp_1) -\
                            timestamp_link_down_t0
                    link_down_lat_link2 = int(link_timestamp_2) -\
                            timestamp_link_down_t0
                    link_down_lat_link3 = int(link_timestamp_3) -\
                            timestamp_link_down_t0
                else:
                    main.log.error("There was an error calculating"+
                        " the delta for link down event")
                    link_down_lat_graph1 = 0
                    link_down_lat_graph2 = 0
                    link_down_lat_graph3 = 0
                    
                    link_down_lat_device1 = 0
                    link_down_lat_device2 = 0
                    link_down_lat_device3 = 0
        
            main.log.report("Link down latency ONOS1 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_down_lat_graph1)+" ms")
            main.log.report("Link down latency ONOS2 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_down_lat_graph2)+" ms")
            main.log.report("Link down latency ONOS3 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_down_lat_graph3)+" ms")
            
            main.log.report("Link down latency ONOS1 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_down_lat_link1)+" ms")
            main.log.report("Link down latency ONOS2 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_down_lat_link2)+" ms")
            main.log.report("Link down latency ONOS3 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_down_lat_link3))
      
            #Calculate avg of node calculations
            link_down_lat_graph_avg =\
                    (link_down_lat_graph1 +
                     link_down_lat_graph2 +
                     link_down_lat_graph3) / 3.0
            link_down_lat_link_avg =\
                    (link_down_lat_link1 +
                     link_down_lat_link2 +
                     link_down_lat_link3) / 3.0

            #Set threshold and append latency to list
            if link_down_lat_graph_avg > 0.0 and\
               link_down_lat_graph_avg < 30000:
                link_down_graph_to_system_list.append(
                        link_down_lat_graph_avg)
            else:
                main.log.info("Link down latency exceeded threshold")
                main.log.info("Results for iteration "+str(i)+
                        "have been omitted")
            if link_down_lat_link_avg > 0.0 and\
               link_down_lat_link_avg < 30000:
                link_down_link_to_system_list.append(
                        link_down_lat_link_avg)
            else:
                main.log.info("Link down latency exceeded threshold")
                main.log.info("Results for iteration "+str(i)+
                        "have been omitted")

            #NOTE: To remove loss rate and measure latency:
            #       'sh tc qdisc del dev s1-eth1 root'
            timestamp_link_up_t0 = time.time() * 1000
            main.Mininet1.handle.sendline("sh tc qdisc del dev "+
                    "s1-eth1 root")
            main.Mininet1.handle.expect("mininet>")
            
            main.log.info("Checking ONOS for link update")
            
            link_down1 = True
            link_down2 = True
            link_down3 = True
            loop_count = 0
            while( (link_down1 and link_down2 and link_down3)\
                    and loop_count < 30 ):
                json_str1 = main.ONOS1cli.links()
                json_str2 = main.ONOS2cli.links()
                json_str3 = main.ONOS3cli.links()
                if not (json_str1 and json_str2 and json_str3):
                    main.log.error("CLI command returned error ")
                    break
                else:
                    json_obj1 = json.loads(json_str1)
                    json_obj2 = json.loads(json_str2)
                    json_obj3 = json.loads(json_str3)
                
                for obj1 in json_obj1:
                    if '01' in obj1['src']['device']:
                        link_down1 = False 
                        main.log.report("Link up from "+
                            "s1 -> s2 on ONOS1 detected")
                for obj2 in json_obj2:
                    if '01' in obj2['src']['device']:
                        link_down2 = False 
                        main.log.report("Link up from "+
                            "s1 -> s2 on ONOS2 detected")
                for obj3 in json_obj3:
                    if '01' in obj3['src']['device']:
                        link_down3 = False 
                        main.log.report("Link up from "+
                            "s1 -> s2 on ONOS3 detected")
                
                loop_count += 1
                time.sleep(1)
            
            if (link_down1 and link_down2 and link_down3):
                main.log.info("Link up discovery failed")
                
                link_up_lat_graph1 = 0
                link_up_lat_graph2 = 0
                link_up_lat_graph3 = 0
                link_up_lat_device1 = 0
                link_up_lat_device2 = 0
                link_up_lat_device3 = 0
                
                assertion = main.FALSE
            else:
                json_topo_metrics_1 =\
                        main.ONOS1cli.topology_events_metrics()
                json_topo_metrics_2 =\
                        main.ONOS2cli.topology_events_metrics()
                json_topo_metrics_3 =\
                        main.ONOS3cli.topology_events_metrics()
                json_topo_metrics_1 = json.loads(json_topo_metrics_1)
                json_topo_metrics_2 = json.loads(json_topo_metrics_2)
                json_topo_metrics_3 = json.loads(json_topo_metrics_3)

                main.log.info("Obtaining graph and device timestamp")
                graph_timestamp_1 = \
                    json_topo_metrics_1[graphTimestamp]['value']
                graph_timestamp_2 = \
                    json_topo_metrics_2[graphTimestamp]['value']
                graph_timestamp_3 = \
                    json_topo_metrics_3[graphTimestamp]['value']

                link_timestamp_1 = \
                    json_topo_metrics_1[linkTimestamp]['value']
                link_timestamp_2 = \
                    json_topo_metrics_2[linkTimestamp]['value']
                link_timestamp_3 = \
                    json_topo_metrics_3[linkTimestamp]['value']

                if graph_timestamp_1 and graph_timestamp_2 and\
                        graph_timestamp_3 and link_timestamp_1 and\
                        link_timestamp_2 and link_timestamp_3:
                    link_up_lat_graph1 = int(graph_timestamp_1) -\
                            timestamp_link_up_t0
                    link_up_lat_graph2 = int(graph_timestamp_2) -\
                            timestamp_link_up_t0
                    link_up_lat_graph3 = int(graph_timestamp_3) -\
                            timestamp_link_up_t0
                
                    link_up_lat_link1 = int(link_timestamp_1) -\
                            timestamp_link_up_t0
                    link_up_lat_link2 = int(link_timestamp_2) -\
                            timestamp_link_up_t0
                    link_up_lat_link3 = int(link_timestamp_3) -\
                            timestamp_link_up_t0
                else:
                    main.log.error("There was an error calculating"+
                        " the delta for link down event")
                    link_up_lat_graph1 = 0
                    link_up_lat_graph2 = 0
                    link_up_lat_graph3 = 0
                    
                    link_up_lat_device1 = 0
                    link_up_lat_device2 = 0
                    link_up_lat_device3 = 0
        
            main.log.info("Link up latency ONOS1 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_up_lat_graph1)+" ms")
            main.log.info("Link up latency ONOS2 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_up_lat_graph2)+" ms")
            main.log.info("Link up latency ONOS3 iteration "+
                    str(i)+" (end-to-end): "+
                    str(link_up_lat_graph3)+" ms")
            
            main.log.info("Link up latency ONOS1 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_up_lat_link1)+" ms")
            main.log.info("Link up latency ONOS2 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_up_lat_link2)+" ms")
            main.log.info("Link up latency ONOS3 iteration "+
                    str(i)+" (link-event-to-system-timestamp): "+
                    str(link_up_lat_link3))
      
            #Calculate avg of node calculations
            link_up_lat_graph_avg =\
                    (link_up_lat_graph1 +
                     link_up_lat_graph2 +
                     link_up_lat_graph3) / 3.0
            link_up_lat_link_avg =\
                    (link_up_lat_link1 +
                     link_up_lat_link2 +
                     link_up_lat_link3) / 3.0

            #Set threshold and append latency to list
            if link_up_lat_graph_avg > 0.0 and\
               link_up_lat_graph_avg < 30000:
                link_up_graph_to_system_list.append(
                        link_up_lat_graph_avg)
            else:
                main.log.info("Link up latency exceeded threshold")
                main.log.info("Results for iteration "+str(i)+
                        "have been omitted")
            if link_up_lat_link_avg > 0.0 and\
               link_up_lat_link_avg < 30000:
                link_up_link_to_system_list.append(
                        link_up_lat_link_avg)
            else:
                main.log.info("Link up latency exceeded threshold")
                main.log.info("Results for iteration "+str(i)+
                        "have been omitted")

        #Calculate min, max, avg of list and report
        link_down_min = min(link_down_graph_to_system_list)
        link_down_max = max(link_down_graph_to_system_list)
        link_down_avg = sum(link_down_graph_to_system_list) / \
                        len(link_down_graph_to_system_list)
        link_up_min = min(link_up_graph_to_system_list)
        link_up_max = max(link_up_graph_to_system_list)
        link_up_avg = sum(link_up_graph_to_system_list) / \
                        len(link_up_graph_to_system_list)

        main.log.report("Link down latency - Min: "+
                str(link_down_min)+"ms  Max: "+
                str(link_down_max)+"ms  Avg: "+
                str(link_down_avg)+"ms")
        main.log.report("Link up latency - Min: "+
                str(link_up_min)+"ms  Max: "+
                str(link_up_max)+"ms  Avg: "+
                str(link_up_avg)+"ms")

        utilities.assert_equals(expect=main.TRUE, actual=assertion,
                onpass="Link discovery latency calculation successful",
                onfail="Link discovery latency case failed")

    def CASE5(self, main):
        '''
        100 Switch discovery latency

        Important:
            This test case can be potentially dangerous if 
            your machine has previously set iptables rules.
            One of the steps of the test case will flush
            all existing iptables rules.
        Note:
            You can specify the number of switches in the 
            params file to adjust the switch discovery size
            (and specify the corresponding topology in Mininet1 
            .topo file)
        '''
        import time
        import subprocess
        import os
        import requests
        import json

        ONOS1_ip = main.params['CTRL']['ip1']
        ONOS2_ip = main.params['CTRL']['ip2']
        ONOS3_ip = main.params['CTRL']['ip3']
        MN1_ip = main.params['MN']['ip1']
        ONOS_user = main.params['CTRL']['user']

        default_sw_port = main.params['CTRL']['port1']
       
        #Number of iterations of case
        num_iter = main.params['TEST']['numIter']
        num_sw = main.params['TEST']['numSwitch']

        #Timestamp 'keys' for json metrics output.
        #These are subject to change, hence moved into params
        deviceTimestamp = main.params['JSON']['deviceTimestamp']
        graphTimestamp = main.params['JSON']['graphTimestamp']
   
        tshark_ofp_output = "/tmp/tshark_ofp_"+num_sw+"sw.txt"
        tshark_tcp_output = "/tmp/tshark_tcp_"+num_sw+"sw.txt"

        tshark_ofp_result_list = []
        tshark_tcp_result_list = []

        main.case(num_sw+" Switch discovery latency")
        main.step("Assigning all switches to ONOS1")
        for i in range(1, int(num_sw)+1):
            main.Mininet1.assign_sw_controller(
                    sw=str(i),
                    ip1=ONOS1_ip,
                    port1=default_sw_port)
        
        #Ensure that nodes are configured with ptpd
        #Just a warning message
        main.log.info("Please check ptpd configuration to ensure"+\
                " All nodes' system times are in sync")
        time.sleep(5)

        for i in range(0, int(num_iter)):
            
            main.step("Set iptables rule to block incoming sw connections")
            #Set iptables rule to block incoming switch connections
            #The rule description is as follows:
            #   Append to INPUT rule,
            #   behavior DROP that matches following:
            #       * packet type: tcp
            #       * source IP: MN1_ip
            #       * destination PORT: 6633
            main.ONOS1.handle.sendline(
                    "sudo iptables -A INPUT -p tcp -s "+MN1_ip+
                    " --dport "+default_sw_port+" -j DROP")
            main.ONOS1.handle.expect("\$") 
            #   Append to OUTPUT rule, 
            #   behavior DROP that matches following:
            #       * packet type: tcp
            #       * source IP: MN1_ip
            #       * destination PORT: 6633
            main.ONOS1.handle.sendline(
                    "sudo iptables -A OUTPUT -p tcp -s "+MN1_ip+
                    " --dport "+default_sw_port+" -j DROP")
            main.ONOS1.handle.expect("\$")
            #Give time to allow rule to take effect
            #NOTE: Sleep period may need to be configured 
            #      based on the number of switches in the topology
            main.log.info("Please wait for switch connection to "+
                    "time out")
            time.sleep(60)
            
            #Gather vendor OFP with tshark
            main.ONOS1.tshark_grep("OFP 86 Vendor", 
                    tshark_ofp_output)
            main.ONOS1.tshark_grep("TCP 74 ",
                    tshark_tcp_output)

            #NOTE: Remove all iptables rule quickly (flush)
            #      Before removal, obtain TestON timestamp at which 
            #      removal took place
            #      (ensuring nodes are configured via ptp)
            #      sudo iptables -F
            
            t0_system = time.time() * 1000
            main.ONOS1.handle.sendline(
                    "sudo iptables -F")

            #Counter to track loop count
            counter_loop = 0
            counter_avail1 = 0
            counter_avail2 = 0
            counter_avail3 = 0
            onos1_dev = False
            onos2_dev = False
            onos3_dev = False
            while counter_loop < 60:
                #Continue to check devices for all device 
                #availability. When all devices in all 3
                #ONOS instances indicate that devices are available
                #obtain graph event timestamp for t1.
                device_str_obj1 = main.ONOS1cli.devices()
                device_str_obj2 = main.ONOS2cli.devices()
                device_str_obj3 = main.ONOS3cli.devices()

                device_json1 = json.loads(device_str_obj1)                
                device_json2 = json.loads(device_str_obj2)                
                device_json3 = json.loads(device_str_obj3)           
                
                for device1 in device_json1:
                    if device1['available'] == True:
                        counter_avail1 += 1
                        if counter_avail1 == int(num_sw):
                            onos1_dev = True
                            main.log.info("All devices have been "+
                                    "discovered on ONOS1")
                    else:
                        counter_avail1 = 0
                for device2 in device_json2:
                    if device2['available'] == True:
                        counter_avail2 += 1
                        if counter_avail2 == int(num_sw):
                            onos2_dev = True
                            main.log.info("All devices have been "+
                                    "discovered on ONOS2")
                    else:
                        counter_avail2 = 0
                for device3 in device_json3:
                    if device3['available'] == True:
                        counter_avail3 += 1
                        if counter_avail3 == int(num_sw):
                            onos3_dev = True
                            main.log.info("All devices have been "+
                                    "discovered on ONOS3")
                    else:
                        counter_avail3 = 0

                if onos1_dev and onos2_dev and onos3_dev:
                    main.log.info("All devices have been discovered "+
                            "on all ONOS instances")
                    json_str_topology_metrics_1 =\
                        main.ONOS1cli.topology_events_metrics()
                    json_str_topology_metrics_2 =\
                        main.ONOS2cli.topology_events_metrics()
                    json_str_topology_metrics_3 =\
                        main.ONOS3cli.topology_events_metrics()
                   
                    #Exit while loop if all devices discovered
                    break 
                
                counter_loop += 1
                #Give some time in between CLI calls
                #(will not affect measurement)
                time.sleep(3)

            main.ONOS1.tshark_stop()
            
            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_ofp_output+" /tmp/") 
            os.system("scp "+ONOS_user+"@"+ONOS1_ip+":"+
                    tshark_tcp_output+" /tmp/")
            ofp_file = open(tshark_ofp_output, 'r')

            #The following is for information purpose only.
            #TODO: Automate OFP output analysis
            main.log.info("Tshark OFP Vendor output: ")
            for line in ofp_file:
                tshark_ofp_result_list.append(line)
                main.log.info(line)

            ofp_file.close()

            tcp_file = open(tshark_tcp_output, 'r')
            main.log.info("Tshark TCP 74 output: ")
            for line in tcp_file:
                tshark_tcp_result_list.append(line)
                main.log.info(line)

            tcp_file.close()

            json_obj_1 = json.loads(json_str_topology_metrics_1)
            json_obj_2 = json.loads(json_str_topology_metrics_2)
            json_obj_3 = json.loads(json_str_topology_metrics_3)

            graph_timestamp_1 = \
                    json_obj_1[graphTimestamp]['value']
            graph_timestamp_2 = \
                    json_obj_2[graphTimestamp]['value']
            graph_timestamp_3 = \
                    json_obj_3[graphTimestamp]['value']

            main.log.info(
                    int(graph_timestamp_1) - int(t0_system))
            main.log.info(
                    int(graph_timestamp_2) - int(t0_system))
            main.log.info(
                    int(graph_timestamp_3) - int(t0_system))