code: def _getTrafficClassAndFlowLabel(self):
          
          if self.tf == 0x0:
              return (self.tc_ecn << 6) + self.tc_dscp, self.flowlabel
          elif self.tf == 0x1:
              return (self.tc_ecn << 6), self.flowlabel
          elif self.tf == 0x2:
              return (self.tc_ecn << 6) + self.tc_dscp, 0
          else:
              return 0, 0
docs: Page 6, draft feb 2011