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Network Testing and Emulation Solutions

Create Python Scripts To Test Layer 4 Traffic

Goal: Create a script to test Layer 4 traffic using Realm

Using the library we will write a script that will allow us to automate the creation of stations and Layer 4 cross connects. We will also be able to start and stop traffic over the cross connects using the script. Station and Cross Connect creation is covered in the Realm Scripting Cookbook. Requires LANforge 5.4.2.
  1. Creating The Profile

    1. We will use the factory method self.local_realm.new_l4_cx_profile() to create our profile object.
    2. After we have done this we can set a few variables for our traffic:
      1. l4_cx_profile.requests_per_ten will set our rate of requests per ten minutes. Setting requests_per_ten = 600 will set our URL request rate to 1 per second. There is no limit to what can be used as the rate but common rates are:
        • 600 : 1/s
        • 1200 : 2/s
        • 1800 : 3/s
        • 2400 : 4/s
      2. l4_cx_profile.url is the URL to be used in the requests. We will also need to specify the direction (dl/ul) and a absolute path for the destination. See syntax here.
        l4_cx_profile.url = "dl /dev/null"
      3. Example Layer 4 profile init:
        class IPV4L4(LFCliBase):
            def __init__(self, host, port, ssid, security, password, url, requests_per_ten, station_list,
                target_requests_per_ten=600, number_template="00000", resource=1, num_tests=1,
            super().__init__(host, port, _debug=_debug_on, _halt_on_error=_exit_on_error, _exit_on_fail=_exit_on_fail)
   = host
            self.port = port
            self.ssid = ssid
   = security
            self.password = password
            self.url = url
            self.requests_per_ten = requests_per_ten
            self.number_template = number_template
            self.sta_list = station_list
            self.resource = resource
            self.num_tests = num_tests
            self.target_requests_per_ten = target_requests_per_ten

            self.local_realm = realm.Realm(, lfclient_port=self.port)
            self.cx_profile = self.local_realm.new_l4_cx_profile()
            self.cx_profile.url = self.url
            self.cx_profile.requests_per_ten = self.requests_per_ten

            # Station Profile init
  2. Starting Traffic

    1. When running traffic, if you plan to measure the rate of requests, it is recommended to do so in 10 minute increments. An example of this can be seen here: To start the traffic we can use the l4_cx_profile.start_cx() method. To stop the traffic we can use the l4_cx_profile.stop_cx() method.
    2. Example start and build method:
      def build(self):
          # Build stations
          self.station_profile.use_security(, self.ssid, self.password)
          print("Creating stations")
          self.station_profile.create(resource=1, radio="wiphy0", sta_names_=self.sta_list, debug=self.debug)
          temp_sta_list = []
          for station in range(len(self.sta_list)):
              temp_sta_list.append(str(self.resource) + "." + self.sta_list[station])

          self.l4_profile.create(ports=temp_sta_list, sleep_time=.5, debug_=self.debug, suppress_related_commands_=None)
      def start(self, print_pass=False, print_fail=False):
          temp_stas = self.sta_list.copy()
          cur_time =
          interval_time = cur_time + datetime.timedelta(minutes=1)
          passes = 0
          expected_passes = 0
          self.local_realm.wait_for_ip(self.resource, temp_stas)
          print("Starting test")
          for test in range(self.num_tests):
              expected_passes += 1
              while cur_time < interval_time:
                  cur_time =

              if self.l4_profile.check_errors(self.debug):
                  if self.__check_request_rate():
                      passes += 1
                      self._fail("FAIL: Request rate did not exceed 90% target rate", print_fail)
                      self._fail("FAIL: Errors found getting to %s " % self.url, print_fail)
                  interval_time = cur_time + datetime.timedelta(minutes=1)
          if passes == expected_passes:
              self._pass("PASS: All tests passes", print_pass)
  3. Examining The Results

    1. We can use http://localhost:8080/layer4/list to check our Layer 4 endpoints. Adding a ,,?fields to the end of the URL will allow us to specify what we want to look at. We can separate fields by commas to show more than one at a time.
      Example: http:/localhost:8080/layer4/list?fields=name,urls/s,total-urls
      • Using total-urls will show us the total requests made.
      • Using urls/s will show us the average URL rate per second.
      • Using rx rate and tx rate will show us the rates of received and transeferred traffic.

      We can also use the url http://localhost:8080/layer4/all to see all of the available fields.
    2. When checking our results for Layer 4 tests we might want to check for common URL related errors:
      • acc. denied will show us the number of times we got an access denied error.
      • bad-url will show us the number of times a request was made with an invalid URL.
      • nf (4xx) will count the number of 400 errors recieved when making requests to our URL.

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