def addTrafficItemPacketStack(self, configElementObj, protocolStackNameToAdd, stackNumber, action='append'):
        """
        Description
           To either append or insert a protocol stack to an existing packet.

           You must know the exact name of the protocolTemplate to add by calling
           showProtocolTemplates() API and get the exact name  as a value for the parameter protocolStackNameToAdd.

           You must also know where to add the new packet header stack.  Use showTrafficItemPacketStack() to see
           your current stack numbers.

           This API returns the protocol stack object handle so you could use it to config its settings.

         Parameters
           configElementObj: /api/v1/sessions/1/ixnetwork/traffic/trafficItem/{id}/configElement/{id}

           action:
               append: To add after the specified stackNumber
               insert: To add before the specified stackNumber

           protocolStackNameToAdd: The name of the protocol stack to add.  To get a list of options,
                                   use API showProtocolTemplates().
                                   Some common ones: MPLS, IPv4, TCP, UDP, VLAN, IGMPv1, IGMPv2, DHCP, VXLAN

           stackNumber: The stack number to append or insert into.
                        Use showTrafficItemPacketStack() to view the packet header stack in order to know
                        which stack number to insert your new stack before or after the stack number.

        Example:
            addTrafficItemPacketStack(configElement, protocolStackNameToAdd='UDP',
                                      stackNumber=3, action='append', apiKey=apiKey, verifySslCert=False

        Returns:
            /api/v1/sessions/1/ixnetwork/traffic/trafficItem/{id}/configElement/{id}/stack/{id}
        """
        if action == 'append':
            action = 'appendprotocol'
        if action == 'insert':
            action = 'insertprotocol'

        # /api/v1/sessions/1
        match = re.match('http.*(/api.*sessions/[0-9]).*', self.ixnObj.sessionUrl)
        if match:
            apiHeader = match.group(1)

        # /api/v1/sessions/1/ixnetwork/traffic/trafficItem/1/configElement/1
        arg1 = configElementObj+'/stack/' + str(stackNumber)

        # Display a list of the current packet stack
        response = self.ixnObj.get(self.ixnObj.httpHeader+configElementObj+'/stack')
        for (index, eachHeader) in enumerate(response.json()):
            self.ixnObj.logInfo('{0}: {1}'.format(index+1, eachHeader['displayName']), timestamp=False)

        # Get a list of all the protocol templates:
        response = self.ixnObj.get(self.ixnObj.sessionUrl+'/traffic/protocolTemplate?skip=0&take=end')

        protocolTemplateId = None
        for eachProtocol in response.json()['data']:
            if bool(re.match('^%s$' % protocolStackNameToAdd, eachProtocol['displayName'].strip(), re.I)):
                # /api/v1/sessions/1/traffic/protocolTemplate/30
                protocolTemplateId =  eachProtocol['links'][0]['href']

        if protocolTemplateId == None:
            raise IxNetRestApiException('No such protocolTemplate name found: {0}'.format(protocolStackNameToAdd))
        self.ixnObj.logInfo('protocolTemplateId: %s' % protocolTemplateId, timestamp=False)
        data = {'arg1': arg1, 'arg2': protocolTemplateId}
        response = self.ixnObj.post(self.ixnObj.httpHeader+configElementObj+'/stack/operations/%s' % action, data=data)

        self.ixnObj.waitForComplete(response, self.ixnObj.httpHeader+configElementObj+'/stack/operations/appendprotocol/'+response.json()['id'])

        # /api/v1/sessions/1/ixnetwork/traffic/trafficItem/1/configElement/1/stack/4
        self.ixnObj.logInfo('addTrafficItemPacketStack: Returning: %s' % response.json()['result'], timestamp=False)
        return response.json()['result']